WO2025247301A1

WO2025247301A1 - Novel antibodies specific for cd98 heavy chain and methods of uses thereof

Info

Publication number: WO2025247301A1
Application number: PCT/CN2025/097902
Authority: WO
Inventors: Qian Liu; Yonghong Zhang; Wei Tang; Xiaolu Yu; Xiaoting TIAN; Ke Zhang; Rongqing ZHAO; Nan Zhang; Chenbing GUAN
Original assignee: Sironax Switzerland GmbH
Current assignee: Sironax Switzerland GmbH
Priority date: 2024-05-30
Filing date: 2025-05-29
Publication date: 2025-12-04
Anticipated expiration: 2026-11-30

Abstract

Disclosed herein are antibodies and antigen-binding domains that specifically bind to human CD98 heavy chain (CD98hc) and their use in, for example, transport across the blood brain barrier (BBB). Among others, bispecific antibodies targeting CD98hc and LILRB2 and their uses in, for example, treating neurological diseases are also provided.

Description

NOVEL ANTIBODIES SPECIFIC FOR CD98 HEAVY CHAIN AND METHODS OF USES THEREOF

This application claims priority to PCT Patent Application No. PCT/CN2024/096369, filed May 30, 2024, and to PCT Patent Application No. PCT/CN2024/142663, filed December 26, 2024, both of which are incorporated herein by reference in their entireties.
1. Reference to Sequence Listing Submitted Electronically

This application incorporates by reference a Sequence Listing entitled 509A001WO03_SL. XML created on May 26, 2025 and having a size of 181,252 bytes.

2. Field

The present invention relates to molecular biology and immunology. Provided herein include antibodies targeting CD98 heavy chain, as well as uses thereof in, for example, transport across blood brain barrier (BBB) .

3. Background

The blood-brain barrier (BBB) is a highly selective permeability barrier that restricts the passage of substances from the bloodstream into the brain, thus posing a significant challenge for delivering therapeutic agents to treat central nervous system (CNS) disorders. Traditional methods of drug delivery are often ineffective, as they fail to cross the BBB in sufficient quantities to exert a therapeutic effect. Recent research has focused on identifying novel methods to enhance drug delivery across the BBB, with one promising approach involving the use of antibodies targeting specific transport mechanisms.

CD98 is a transmembrane protein expressed on the surface of various cell types, including those at the BBB. It plays a crucial role in amino acid transport and cellular signaling. Targeting CD98 with antibodies offers a potential pathway to facilitate the transport of therapeutic agents into the brain via receptor-mediated transcytosis. Despite the potential, therapeutics targeting CD98 in treating neurological diseases are currently lacking. The compositions and methods provided herein meet this unmet need and provide other relative advantages.

4. Summary

Provided herein are antibody or antigen-binding fragment thereof that specifically binds human CD98 heavy chain (CD98hc) , comprising a heavy chain variable region (VH) comprising VH CDR1, VH CDR2, and VH CDR3 and a light chain variable region (VL) comprising VL CDR1, VL CDR2, and VL CDR3; having the amino acid sequences of (1) SEQ ID NOs: 25, 26, 27, 28, 29, and 30, respectively; (2) SEQ ID NOs: 31, 32, 33, 34, 35, and 36; (3) SEQ ID NOs: 37, 38, 39, 40, 41, and 42, respectively; (4) SEQ ID NOs: 43, 44, 45, 46, 47, and 48, respectively; (5) SEQ ID NOs: 49, 50 (or 118) , 51, 52, 53, and 54, respectively; (6) SEQ ID NOs: 55, 56, 57, 58, 59, and 60, respectively; (7) SEQ ID NOs: 61, 62, 63, 64, 65, and 66, respectively; (8) SEQ ID NOs: 67, 68, 69, 70, 71, and 72, respectively; (9) SEQ ID NOs: 73, 74, 75 (or 119) , 76, 77, and 78, respectively; or (10) SEQ ID NOs: 79, 80, 81, 82, 83, and 84, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and/or up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

In some embodiments, the antibody or antigen-binding fragment described herein comprises a VH and a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequences of (1) SEQ ID NO: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively.

In some embodiments, the antibody or antigen-binding fragment described herein is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment. In some embodiments, the antibody or antigen-binding fragment described herein is a humanized antibody or antigen-binding fragment.

In some embodiments, the humanized antibody or antigen-binding fragment described herein comprises (a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to SEQ ID NO: 113. In some embodiments, the humanized antibody or antigen-binding fragment described herein comprises (a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110 and 137; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 103 or 105.

In some embodiments, the antibody or antigen-binding fragment described herein comprises a VL and a VH having the amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.

In some embodiments, the antibody or antigen-binding fragment described herein is selected from the group consisting of a Fab, a Fab’ , a F (ab’ ) 2, a Fv, a scFv, a (scFv) 2, a single domain antibody (sdAb) , and a heavy chain antibody (HCAb) .

In some embodiments, the antibody or antigen-binding fragment described herein is an scFv, wherein the scFv comprises from N terminus to C terminus, the VH, a linker, and the VL; or the VL, a linker, and the VH. In some embodiments, the linker has an amino acid sequence selected from the group consisting of SEQ ID NOs: 130-132.

In some embodiments, the antibody is an IgG1 antibody, an IgG2 antibody, an IgG3 antibody, or an IgG4 antibody.

Provided herein are also an antibody or antigen-binding fragment thereof that competes with the antibody or antigen-binding fragment described herein for binding to human CD98hc. In some embodiments, the antibody or antigen-binding fragment described herein is a bispecific antibody or a multispecific antibody. In some embodiments, the antibody or antigen-binding fragment described herein is a monoclonal antibody or antigen-binding fragment.

The antibody or antigen-binding fragment described herein is an internalizing antibody or antigen binding fragment. In some embodiments, the antibody or antigen-binding fragment described herein can cross the blood brain barrier (BBB) . In some embodiments, the antibody or antigen binding fragment does not inhibit leucine uptake.

Provided herein are also methods of making an antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising culturing the cell described herein under conditions that allow expression of the antibody or antibody fragment. In some embodiments, the method described herein that comprises isolating the antibody from the culture.

Provided herein are conjugates comprising the antibody or antigen-binding fragment described herein linked to an effector moiety. In some embodiments, the effector moiety is selected from the group consisting of drugs for neurological diseases or disorders, neurotrophic factors, growth factors, enzymes, cytotoxic agents and imaging agents.

Provided herein are also methods of delivering an effector moiety across BBB in a subject comprising administering to a subject a conjugate comprising the antibody or antigen-binding fragment described herein linked to the effector moiety.

Provided herein are also fusion proteins comprising the antibody or antigen-binding fragment described herein linked to a second antibody or antigen-binding fragment that specifically binds to a central nervous system (CNS) antigen. In some embodiments, the CNS antigen is selected from the group consisting of alpha-synuclein, amyloid precursor protein (APP) , amyloid-beta (Aβ) , apolipoprotein E (ApoE) , apolipoprotein E4 (ApoE4) , ATP-binding cassette sub-family A member 1 (ABCA1) , ATP-binding cassette sub-family A member 7 (ABCA7) , beta-secretase 1 (BACE1) , caspase 6, CD20, CD33 (Siglec3) , death receptor 6 (DR6) , disialoganglioside (GD2) , epidermal growth factor (EGF) , epidermal growth factor receptor (EGFR) , epidermal growth factor receptor 2 (EGFR2/HER2) , gamma secretase, glycoprotein nonmetastatic melanoma protein B (GPNMB) , HLA-DR1, HLA-DR5, huntingtin, IL-34, IL1RAP, interleukin-13 receptor alpha 2 (IL-13Rα2) , leucine-rich repeat kinase 2 (LRRK2) , LILRB2, matrix metalloproteinases (MMPs) , membrane spanning 4-domains A4A (MS4A4A) , membrane spanning 4-domains A4E (MS4A4E) , membrane spanning 4-domains A 6A (MS4A6A) , p-glucocerebrosidase (GCase or GBA) , p75 neurotrophin receptor (p75NTR) , parkin, paired immunoglobin like type 2 receptor alpha (PILRA) , phosphorylated Tau, prion protein (PrP) , presenilin 1, presenilin 2, progranulin (PGRN) , prosaposin (PSAP) , sialic acid binding Ig-like lectin 11 (Siglec11) , sialic acid binding Ig-like lectin 5 (Siglec5) , sialic acid binding Ig-like lectin 7 (Siglec7) , sialic acid binding Ig-like lectin 9 (Siglec9) , sortilin (SORT) , sphingolipids, Tau protein, transmembrane protein 106B (TMEM106b) , triggering receptor expressed on myeloid cells 2 (TREM2) , TXNRD1, and ubiquitin protein ligase E3A (UBE3A) .

In some embodiments, the fusion protein described herein is a bispecific antibody. In some embodiments, the fusion protein described herein comprises an IgG that specifically binds to the CNS antigen and an scFv that specifically binds to CD98hc. In some embodiments, the scFv is linked to the C terminus of a heavy chain of the IgG. In some embodiments, the CNS antigen is LILRB2. In some embodiments, the antibody that specifically binds to LIBRB2 comprises a VH having VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 122, 123 and 124, respectively, and a VL having VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 125, 126, and 127 respectively. In some embodiments, the antibody that specifically binds to LIBRB2 comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 120 and 121, respectively.

Provided herein are bispecific antibodies for CD98hc and LILBR2, comprising (1) a first peptide chain (HC1) comprising, from N-terminus to C-terminus, VH1 and a first CH region, and a scFv; (2) a second peptide chain (HC2) comprising, from N-terminus to C-terminus, VH1 and a second CH region; and (3) a third peptide chain (LC) comprising, from N-terminus to C-terminus, VL1 and a CL region; wherein (i) the VH1 and VL1 have the amino acid sequences of SEQ ID NOs: 120 and 121, respectively; and (ii) the scFv comprises VH2 and VL2 having the amino acid sequences of (1) SEQ ID NOs: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively; or humanized versions thereof.

In some embodiments, the VH2 and VL2 have amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.

In some embodiments, the scFv has at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-101 and 138.

In some embodiments, the CL region is Cκ. In some embodiments, the first CH region further has T350V, L351Y, F405A, and Y407V substitutions and the second CH region has T350V, T366L, K392L, and T394W substitutions. In some embodiments, the first CH region further has T366W substitution, and the second CH region further has T366S, L368A, and Y407V substitutions. In some embodiments, the first and second CH regions further have L234A, L235A, and D266S substitutions (AAS mutations) , or M252Y, S254T, and T256E (YTE mutations) , or both AAS mutations and YTE mutations. In some embodiments, the second CH region further has H435R and Y436F substitutions.

In some embodiments, the HC1, HC2, and LC of the bispecific antibodies described herein are at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to amino acid sequences of (1) SEQ ID NOs: 85, 86, and 87, respectively; (2) SEQ ID NOs: 88, 86, and 87, respectively; (3) SEQ ID NOs: 89, 86, and 87, respectively; (4) SEQ ID NOs: 90, 86, and 87, respectively; or (5) SEQ ID NOs: 91, 86, and 87, respectively.

In some embodiments, provided herein are polynucleotides encoding a polypeptide of the antibody or antigen-binding fragment described herein. Provided herein are polynucleotide or a plurality of polynucleotide that encodes or collectively encode the three peptide chains of the bispecific antibody described herein. In some embodiments, provided herein are vectors comprising the polynucleotide disclosed herein. In some embodiments, provided herein are host cells comprising the polynucleotide or plurality of nucleotide disclosed herein, or the vector described herein.

Provided herein are also methods of making a bispecific antibody that specifically binds human CD98hc, comprising culturing the cell described herein under conditions that allow expression of the bispecific antibody. In some embodiments, methods provided herein comprise isolating the antibody from the culture.

Provided herein are pharmaceutical compositions comprising a therapeutically effective amount of the fusion protein (e.g., bispecific antibody) described herein and a pharmaceutically acceptable carrier.

Provided herein are also methods of treating a neurological disease or disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the fusion protein (e.g., bispecific antibody) described herein. In some embodiments, the neurological disease or disorder is a neurodegenerative disease. In some embodiments, methods provided herein further comprise administering an additional therapy to the subject. In some embodiments, the subject is a human.

5. Brief Description of Drawings

FIGs. 1A-1C provides flow cytometry results showing the binding of ten candidate antibodies to HEK293 cells overexpressing huCD98c (FIG. 1A) , CHO cells overexpressing Cyno CD98hc (FIG. 1B) , and wildtype CHO cells (FIG. 1C) .

FIG. 2 provides results of pHrodo labeling based high-content imaging assay for measuring the internalizing activities of candidate antibodies.

FIG. 3 provides results of leucine uptake inhibition assay for the candidate antibodies.

FIG. 4 provides results of pHrodo labeling based high-content imaging assay for measuring the internalizing activities of candidate bispecific antibodies

FIG. 5 provides the plasma levels of candidate bispecific antibodies after administered into human CD98 knock-in mice over time.

FIG. 6 provides the relative levels of candidate bispecific antibodies in brain 24 hours after administered into human CD98 knock-in mice.

FIG. 7 provides the relative levels of candidate bispecific antibodies in brain parenchyma 24 hours after administered into human CD98 knock-in mice.

FIG. 8 provides the relative levels of candidate humanized bispecific antibodies in brain cells 24 hours and 72 hours after administered into human CD98 knock-in mice.

FIG. 9 provides the relative levels of candidate humanized bispecific antibodies in brain parenchyma 24 hours and 72 hours after administered into human CD98 knock-in mice.

FIG. 10 provides serum clearance in non-human primates (NHPs) for LILRB2-CD98hc (anti-LILRB2/CD98hc bsAb) , LILRB2-TfR (anti-LILRB2/TfR bsAb) , and LILRB2 (anti-LILRB2) .

FIG. 11 provides NHP CSF PK for LILRB2-CD98hc (anti-LILRB2/CD98hc bsAb) , LILRB2-TfR (anti-LILRB2/TfR bsAb) , and LILRB2 (anti-LILRB2) .

6. Detailed Description

The present disclosure provides novel antibodies targeting human CD98 heavy chain (CD98hc) and their uses in transport across BBB. Conjugates (e.g., fusion proteins) comprising such antibodies, pharmaceutical compositions comprising such conjugates, and their uses in, for example, treating neurological diseases are also provided herein.

CD98, also known as 4F2hc or SLC3A2, is a transmembrane glycoprotein that plays a pivotal role in cellular processes including amino acid transport, cell proliferation, and integrin signaling. It is ubiquitously expressed in a variety of tissues, with particularly high expression in rapidly dividing cells and at the interfaces between tissues and the external environment, such as the BBB. CD98 forms a heterodimer with various light chains, such as LAT1 (SLC7A5) and LAT2 (SLC7A8) , which are essential for the transport of neutral amino acids across the plasma membrane.

Structurally, CD98 consists of a heavy chain (4F2hc) and a light chain, linked by a disulfide bond. The heavy chain is responsible for the protein's trafficking to the plasma membrane, while the light chain carries out the amino acid transport function. This heterodimeric configuration allows CD98 to participate in essential nutrient transport and cellular signaling pathways. Functionally, CD98 is involved in integrin signaling, which influences cell adhesion, migration, and proliferation, making it a critical player in both normal physiology and pathological conditions.

As used herein, the terms “CD98hc” and “CD98hc peptide” are used interchangeably to refer to any native CD98hc from any vertebrate source, including mammals such as primates (e.g., humans and cynomolgus monkeys (cynos) ) and rodents (e.g., mice and rats) , unless otherwise indicated. CD98hc is also referred to as 4F2 cell-surface antigen heavy chain, 4F2hc, 4F2 heavy chain antigen, lymphocyte activation antigen 4F2 large subunit, solute carrier family 3 member 2, and CD98. CD98hc protein is encoded by the SLC3A2 gene and is part of the large amino acid transporter (LAT) complex. The term encompasses both wild-type sequences and naturally occurring variant sequences, e.g., splice variants or allelic variants. The term encompasses full-length, unprocessed CD98hc, as well as any form of CD98hc that results from processing in the cell. In some embodiments, the CD98hc is human CD98hc. An exemplary full length human CD98hc sequence is provided below.

More information about human CD98hc can be found on public databases with the following IDs: HGNC: 11059; NCBI Entrez Gene: 6520; Ensembl: ENSG00000117399; 158070; UniProtKB/Swiss-Prot: P08195. Five (5) alternatively spliced transcript variants encoding different isoforms are described for the human CD98hc gene (Uniprot NOs: P08195-1 to P08195-5) .

Before the present disclosure is further described, it is to be understood that the disclosure is not limited to the particular embodiments set forth herein, and it is also to be understood that the terminology used herein is for the purpose of describing particular embodiments, and is not intended to be limiting.
6.1 Definitions

Unless otherwise defined herein, scientific and technical terms used in the present disclosures shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. Generally, nomenclatures used in connection with, and techniques of, cell and tissue culture, molecular biology, immunology, microbiology, genetics and protein and nucleic acid chemistry and hybridization described herein are those well-known and commonly used in the art.

The term “a” or “an” entity refers to one or more of that entity; for example, “an antibody, ” is understood to represent one or more antibodies.

The term “and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. Thus, the term “and/or” as used in a phrase such as “A and/or B” herein is intended to include “A and B, ” “A or B, ” “A” (alone) , and B” (alone) . Likewise, the term “and/or” as used in a phrase such as “A, B, and/or C” is intended to encompass each of the following aspects: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone) ; B (alone) ; and C (alone) .

As used herein, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects. The term “about” encompasses the exact number recited. In some embodiments, “about” means within plus or minus 10%of a given value or range. In certain embodiments, “about” means that the variation is ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.2%, or ±0.1%of the value to which “about” refers. In some embodiments, “about” means that the variation is ±1%, ±0.5%, ±0.2%, or ±0.1%of the value to which “about” refers.

As used herein and consistent with its understanding in the art, the terms “central nervous system” and “CNS” refer to the complex of nerve tissues that control bodily function and includes the brain and spinal cord.

As used herein and consistent with its understanding in the art, the terms “central nervous system antigen” or “CNS antigen” refer to an antigen expressed in the CNS, including the brain, which can be targeted with an effect moiety, such as an antibody or small molecule. A “brain antigen” refers to a CNS antigen expressed in the brain.

As used herein and consistent with its understanding in the art, the term “neurological disease or disorder” refers to a disease or disorder which affects the nervous system, which includes the brain, spinal cord, and peripheral nerves. These diseases or disorders can arise from a variety of causes, including genetic mutations, developmental issues, infections, trauma, and degenerative diseases. Neurological diseases or disorders can manifest in a wide range of symptoms depending on the affected area and function of the nervous system. Common symptoms include seizures, muscle weakness, poor coordination, pain, altered levels of consciousness, and cognitive impairments.

As used herein and consistent with its understanding in the art, the term “neurodegenerative disease” is a type of neurological disease or disorder characterized by the progressive degeneration of the structure and function of the nervous system. These diseases primarily affect neurons, which are the building blocks of the nervous system, leading to their gradual loss and eventual death. Neurodegenerative diseases are often associated with aging and typically result in cognitive, motor, and functional impairments. The exact causes of many neurodegenerative diseases are still not fully understood, but they often involve genetic, environmental, and lifestyle factors.

As used herein and consistent with its understanding in the art, the terms “blood brain barrier” and “BBB” refer to a network of endothelial cells that are closely sealed by tight junctions and characterized by low levels of nonspecific paracellular and transcellular transport. The BBB separates the circulating blood from the brain and extracellular fluid in the CNS to protect the brain from pathogens and toxins, while allowing essential nutrients to pass through. A molecule can “cross” the BBB means that the molecule has the capability to traverse the BBB to reach and acting on CNS targets. A molecule can cross the BBB via a variety of mechanisms, including lipophilicity, transporter-mediated transcytosis, receptor-mediated transcytosis, or simply small size.

The terms “polypeptide, ” “peptide, ” “protein, ” “polypeptide chain, ” “peptide chain, ” and their grammatical equivalents as used interchangeably herein refer to polymers of amino acids of any length, which can be linear or branched. It can include unnatural or modified amino acids or be interrupted by non-amino acids. A polypeptide, peptide, polypeptide chain, peptide chain, or protein can also be modified with, for example, disulfide bond formation, glycosylation, lipidation, acetylation, phosphorylation, or any other manipulation or modification.

The terms “polynucleotide, ” “nucleic acid, ” and their grammatical equivalents as used interchangeably herein mean polymers of nucleotides of any length and include DNA and RNA. The nucleotides can be deoxyribonucleotides, ribonucleotides, modified nucleotides or bases, and/or their analogs, or any substrate that can be incorporated into a polymer by DNA or RNA polymerase.

As used herein and understood in the art, an “antibody” is an immunoglobulin molecule that recognizes and specifically binds a target (e.g., a protein) through at least one antigen-binding fragment which is typically within the variable region of the immunoglobulin molecule. An “antibody” can be of many different types and structures. For example, antibodies can be polyclonal antibodies, monoclonal antibodies, multispecific antibodies, bispecific antibodies, monospecific antibodies, monovalent antibodies, or any other modified immunoglobulin molecule comprising an antigen-binding site. Antibodies also include, but are not limited to, mouse antibodies, camel antibodies, chimeric antibodies, humanized antibodies, and human antibodies. An antibody can be any of the five major classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, or subclasses (isotypes) thereof (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) , based on the identity of their heavy-chain constant domains referred to as alpha, delta, epsilon, gamma, and mu, respectively. Unless expressly indicated otherwise, the term “antibody” as used herein include “antigen-binding fragment” of intact antibodies. The term “antigen-binding fragment” as used herein refers to a portion or fragment of an intact antibody that is the antigenic determining variable region of an intact antibody. Examples of antigen-binding fragments include, but are not limited to, Fab, Fab', F (ab’ ) 2, Fv, linear antibodies, single chain antibody molecules (e.g., scFv) , heavy chain antibodies (HCAbs) , light chain antibodies (LCAbs) , disulfide-linked scFv (dsscFv) , diabodies, tribodies, tetrabodies, minibodies, dual variable domain antibodies (DVD) , single variable domain antibodies (sdAbs; e.g., camelid antibodies, alpaca antibodies) , and single variable domain of heavy chain antibodies (VHH) .

The structure of immunoglobulins has been well characterized (see, e.g., FUNDAMENTAL IMMUNOLOGY Ch. 7 (Paul, W., ed., 2nd ed. Raven Press, N.Y. (1989) ) . Typically, immunoglobulins comprise two pairs of polypeptide chains, one pair of light (L; low molecular weight) chains and one pair of heavy (H; high molecular weight) chains, all four inter-connected by disulfide bonds.

Each light chain of an immunoglobulin typically includes a light chain variable region ( “VL region” ) and a light chain constant region ( “CL region” ) . There are two distinct types of light chains, referred to as kappa (κ) of lambda (λ) based on the amino acid sequence of the CL region. The amino acid sequences of the CL regions are well known in the art.

Each heavy chain typically includes a heavy chain variable region (a “VH region” ) and a heavy chain constant region (a “CH region” ) . The VH region can be one of five distinct types, referred to as alpha (α) , delta (δ) , epsilon (ε) , gamma (γ) and mu (μ) , based on the amino acid sequence. When combined with a light chain, these distinct types of heavy chains give rise to five well known classes of antibodies, IgA, IgD, IgE, IgG and IgM, respectively. There are four subclasses of IgG, namely, IgG1, IgG2, IgG3 and IgG4. The amino acid sequences of the CH regions of different classes of antibodies are well known in the art.

The CH region of immunoglobulins comprise more than one domain. For example, the CH region of an IgG antibody is comprised of three domains, heavy chain constant domain 1 (CH1) , heavy chain constant domain 2 (CH2) , and heavy chain constant domain 3 (CH3) . The highly flexible region between the CH1 and CH2 domains is referred to as the “hinge region. ” Disulfide bonds in the hinge region are part of the interactions between two heavy chains in an immunoglobulin. The “Fc region” refers to the C-terminal region of an immunoglobulin heavy chain that contains at least a portion of the constant region. In IgG, IgA and IgD isotypes, the Fc region is comprised of the hinge region, the CH2 domain and the CH3 domain; IgM and IgE Fc regions contain three heavy chain constant domains (CH domains 2–4) . The amino acid sequences of the Fc region of human IgG, IgA, IgD, IgM and IgE, and subtypes IgG1, IgG2, IgG3, and IgG4 are known to those of ordinary skill in the art. In some embodiments, the Fc region of an IgG heavy chain can extend from the hinge region to the carboxyl-terminus of the heavy chain. The native Fc regions can be modified. Modification of the Fc regions are further described below. In some embodiments, a bispecific antibody provided herein can comprise paired Fc domains comprising paired different modifications that promote their association with each other, instead of forming homodimers.

Unless otherwise stated or contradicted by context, reference to amino acid positions in the constant regions is according to the EU-numbering (Edelman et al., PNAS. 1969; 63: 78-85, Kabat et al., Sequences of Proteins of Immunological Interest, Fifth Edition. 1991 NIH Publication No. 91-3242) .

The term “variable region” refers to a portion of the light or heavy chains of an immunoglobulin that is generally located at the amino-terminal of the light or heavy chain and used in the binding and specificity of each particular antibody for its particular antigen. The variable region of a light chain is referred to as a “light chain variable region” or “VL region, ” which includes at least one, typically one, “light chain variable domain” or “VL. ” The variable region of a heavy chain is referred to as a “heavy chain variable region” or “VH region, ” which includes at least one, typically one, “heavy chain variable domain” or “VH. ” The variable domains differ extensively in sequence between different antibodies. A “pair of VL and VH” or “VH/VL pair” can associate with each other and form a binding site that specifically binds the target antigen or epitope.

The VH and VL regions can be further subdivided into regions of hypervariability (or hypervariable regions which may be hypervariable in sequence and/or form of structurally defined loops) , also termed complementarity determining regions (CDRs) , interspersed with regions that are more conserved, termed framework regions (FRs) . The variability in sequence is concentrated in the CDRs while the less variable portions in the variable domain are referred to as framework regions (FR) . The CDRs of the light and heavy chains are primarily responsible for the interaction of the antibody with antigen. Each VH and VL is typically composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4 (see also Chothia and Lesk, J Mol Biol. 1987; 196: 901-17) .

A CDR refers to one of three hypervariable regions (H1, H2 or H3) within the non-framework region of the immunoglobulin (Ig or antibody) VH β-sheet framework, or one of three hypervariable regions (L1, L2 or L3) within the non-framework region of the antibody VL β-sheet framework. CDR regions are well known to those skilled in the art and have been defined by a variety of methods/systems. These systems and/or definitions include, for example, Kabat, Chothia, IMGT, AbM, and Contact. For example, Kabat defines the regions of most hypervariability within the antibody variable (V) domains (Kabat et al., J. Biol. Chem. 252: 6609-6616 (1977) ; Kabat, Adv. Prot. Chem. 32: 1-75 (1978) ) . Software programs (e.g., abYsis) are available and known to those of skill in the art for analysis of antibody sequence and determination of CDRs.

A CDR refers to one of three hypervariable regions (H1, H2 or H3) within the non-framework region of the immunoglobulin (Ig or antibody) VH β-sheet framework, or one of three hypervariable regions (L1, L2 or L3) within the non-framework region of the antibody VL β-sheet framework. Accordingly, CDRs are variable region sequences interspersed within the framework region sequences. CDR regions are well known to those skilled in the art and have been defined by a variety of methods/systems. These systems and/or definitions have been developed and refined over years and include Kabat, Chothia, IMGT, AbM, and Contact. For example, Kabat defines the regions of most hypervariability within the antibody variable (V) domains (Kabat et al, J. Biol. Chem. 252: 6609-6616 (1977) ; Kabat, Adv. Prot. Chem. 32: 1-75 (1978) ) . The Chothia definition is based on the location of the structural loop regions, which defines CDR region sequences as those residues that are not part of the conserved β-sheet framework, and thus are able to adapt different conformations (Chothia and Lesk, J. Mol. Biol. 196: 901-917 (1987) ) . Both terminologies are well recognized in the art. Additionally, the IMGT system is based on sequence variability and location within the structure of the variable regions. The AbM definition is a compromise between Kabat and Chothia. The Contact definition is based on analyses of the available antibody crystal structures. Software programs (e.g., abYsis) are available and known to those of skill in the art for analysis of antibody sequence and determination of CDRs. The positions of CDRs within a canonical antibody variable domain have been determined by comparison of numerous structures (Al-Lazikani et al, J. Mol. Biol. 273: 927-948 (1997) ; Morea et al, Methods 20: 267-279 (2000) ) . Because the number of residues within a hypervariable region varies in different antibodies, additional residues relative to the canonical positions are conventionally numbered with a, b, c and so forth next to the residue number in the canonical variable domain numbering scheme (Al-Lazikani et al., supra (1997) ) . Such nomenclature is similarly well known to those skilled in the art.

For example, CDRs defined according to either the Kabat (hypervariable) or Chothia (structural) designations, are set forth in the table below.

¹Residue numbering follows the nomenclature of Kabat et al., supra
²Residue numbering follows the nomenclature of Chothia et al., supra

A single chain Fv ( “scFv” ) polypeptide is a covalently linked VL/VH heterodimer which is usually expressed from a gene fusion including VL and VH-encoding genes linked by a peptide-encoding linker. The scFv fragment includes CDRs that are held in appropriate conformation, in particular by using gene recombination techniques. In some embodiments of scFvs, the N-terminus of VL is linked to the C-terminus of the VH via a linker. In some embodiments of scFvs, the N-terminus of VH is linked to the C-terminus of the VL via a linker.

As used herein and understood in the art, a “bispecific” antibody is an artificial hybrid antibody having two different antigen binding fragments. In some embodiments, the two different antigen binding fragments specifically bind two different target antigens. In some embodiments, the two different antigen binding fragments specifically bind two different epitopes on the same target antigen. In some embodiments, the bispecific antibodies provided herein comprise an antigen binding fragment that specifically binds to human CD98hc and an antigen binding fragment that that specifically binds to human LILRB2. Bispecific antibodies can be formed from antibody fragments.

As used herein and understood in the art, an “internalizing” antibody or an “internalization” antibody refers to an antibody that, upon binding to its target antigen on the surface of a cell, is actively transported into the interior of the cell. This process, known as internalization, involves the antibody-antigen complex being engulfed by the cell membrane and then transported into the cell via endocytosis or other cellular uptake mechanisms. Internalizing antibodies are particularly useful in therapeutic and diagnostic applications because they can deliver attached therapeutic agents, such as drugs or toxins, directly into the target cells. This targeted delivery can enhance the efficacy and specificity of the treatment while minimizing off-target effects. In contrast, non-internalizing antibodies bind to their target antigens on the cell surface but do not undergo endocytosis. Non-internalizing therapeutic antibodies exert their therapeutic effects extracellularly. Non-internalizing antibodies can be used for a variety of purposes, such as blocking receptor-ligand interactions, recruiting immune cells to destroy the target cell via mechanisms like antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) , and neutralizing toxins or pathogens in the bloodstream.

The term “linker” as used herein refers to one or more amino acid residues inserted between domains (e.g., immunoglobulin domains) to provide sufficient mobility for the domains. A linker can be inserted at the transition between variable domains or between variable and constant domains, respectively, at the sequence level.

The term “humanized antibody” as used herein refers to forms of non-human (e.g., murine) antibodies that are specific immunoglobulin chains, chimeric immunoglobulins, or fragments thereof that contain minimal non-human sequences. Typically, humanized antibodies are human immunoglobulins. In some instances, the variable region residues of a human immunoglobulin are replaced with the corresponding residues in an antibody from a non-human species. In some instances, residues of the CDRs are replaced by residues from the CDRs of a non-human species (e.g., mouse, rat, hamster, camel) that have the desired specificity, affinity, and/or binding capability. The humanized antibody can be further modified by the substitution of additional residues either in the variable region and/or within the replaced non-human residues to refine and optimize antibody specificity, affinity, and/or binding capability.

The term “variant” as used herein in relation to a protein or a polypeptide with particular sequence features (the “reference protein” or “reference polypeptide” ) refers to a different protein or polypeptide having one or more (such as, for example, about 1 to about 25, about 1 to about 20, about 1 to about 15, about 1 to about 10, or about 1 to about 5) amino acid substitutions, deletions, and/or additions as compared to the reference protein or reference polypeptide. The changes to an amino acid sequence can be amino acid substitutions. The changes to an amino acid sequence can be conservative amino acid substitutions. A functional fragment or a functional variant of a protein or polypeptide maintains the basic structural and functional properties of the reference protein or polypeptide.

The term “specifically binds, ” as used herein, means that a polypeptide or molecule interacts more frequently, more rapidly, with greater duration, with greater affinity, or with some combination of the above to the epitope, protein, or target molecule than with alternative substances, including related and unrelated proteins. A binding moiety (e.g., antibody) that specifically binds a target molecule (e.g., antigen) can be identified, for example, by immunoassays, ELISAs, Bio-Layer Interferometry ( “BLI” ) , SPR (e.g., Biacore) , or other techniques known to those of skill in the art. Typically, a specific reaction will be at least twice background signal or noise and can be more than 10 times background. See, e.g., Paul, ed., 1989, FUNDAMENTAL IMMUNOLOGY SECOND EDITION, Raven Press, New York at pages 332-336 for a discussion regarding antibody specificity. A binding moiety that specifically binds a target molecule can bind the target molecule at a higher affinity than its affinity for a different molecule. In some embodiments, a binding moiety that specifically binds a target molecule can bind the target molecule with an affinity that is at least 20 times greater, at least 30 times greater, at least 40 times greater, at least 50 times greater, at least 60 times greater, at least 70 times greater, at least 80 times greater, at least 90 times greater, or at least 100 times greater, than its affinity for a different molecule. In some embodiments, a binding moiety that specifically binds a particular target molecule binds a different molecule at such a low affinity that binding cannot be detected using an assay described herein or otherwise known in the art. In some embodiments, “specifically binds” means, for instance, that a binding moiety binds a molecule target with a K_D of about 0.1 mM or less. In some embodiments, “specifically binds” means that a polypeptide or molecule binds a target with a K_D of at about 10 μM or less or about 1 μM or less. In some embodiments, “specifically binds” means that a polypeptide or molecule binds a target with a K_D of at about 0.1 μM or less, about 0.01 μM or less, or about 1 nM or less. Because of the sequence identity between homologous proteins in different species, specific binding can include a polypeptide or molecule that recognizes a protein or target in more than one species. Likewise, because of homology within certain regions of polypeptide sequences of different proteins, specific binding can include a polypeptide or molecule that recognizes more than one protein or target. It is understood that, in some embodiments, a binding moiety (e.g., antibody) that specifically binds a first target may or may not specifically bind a second target. As such, “specific binding” does not necessarily require (although it can include) exclusive binding, i.e., binding to a single target. Thus, a binding moiety (e.g., antibody) can, in some embodiments, specifically bind more than one target. For example, an antibody can, in certain instances, comprise two identical antigen-binding sites, each of which specifically binds the same epitope on two or more proteins. In certain alternative embodiments, an antibody can be bispecific and comprise at least two antigen-binding sites with differing specificities.

The term “binding affinity” as used herein generally refers to the strength of the sum total of noncovalent interactions between a binding moiety and a target molecule (e.g., antigen) . The binding of a binding moiety and a target molecule is a reversible process, and the affinity of the binding is typically reported as an equilibrium dissociation constant (K_D) . K_D is the ratio of a dissociation rate (k_off or k_d) to the association rate (k_on or k_a) . The lower the K_D of a binding pair, the higher the affinity. A variety of methods of measuring binding affinity are known in the art, any of which can be used for purposes of the present disclosure. Specific illustrative embodiments include the following. In some embodiments, the “K_D” or “K_D value” can be measured by assays known in the art, for example by a binding assay. The K_D may be measured in a radiolabeled antigen binding assay (RIA) (Chen, et al., (1999) J. Mol Biol 293: 865-881) . The K_D or K_D value can also be measured by using biolayer interferometry (BLI) using, for example, the Gator system (Probe Life) , or the Octet-96 system (Sartorius AG) . The K_D or K_D value can also be measured by using surface plasmon resonance assays (SPR) by Biacore, using, for example, a BIAcoreTM-2000 or a BIAcoreTM-3000 BIAcore, Inc., Piscataway, NJ) .

The terms “identical, ” percent “identity, ” and their grammatical equivalents as used herein in the context of two or more polynucleotides or polypeptides, refer to two or more sequences or subsequences that are the same or have a specified percentage of nucleotides or amino acid residues that are the same, when compared and aligned (introducing gaps, if necessary) for maximum correspondence, not considering any conservative amino acid substitutions as part of the sequence identity. The percent identity can be measured using sequence comparison software or algorithms or by visual inspection. Various algorithms and software that can be used to obtain alignments of amino acid or nucleotide sequences are well-known in the art. These include, but are not limited to, BLAST, ALIGN, Megalign, BestFit, GCG Wisconsin Package, and variants thereof. In some embodiments, two polynucleotides or polypeptides provided herein are substantially identical, meaning they have at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, and in some embodiments at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%nucleotide or amino acid residue identity, when compared and aligned for maximum correspondence, as measured using a sequence comparison algorithm or by visual inspection. In some embodiments, identity exists over a region of the amino acid sequences that is at least about 10 residues, at least about 20 residues, at least about 40-60 residues, at least about 60-80 residues in length or any integral value there between. In some embodiments, identity exists over a longer region than 60-80 residues, such as at least about 80-100 residues, and in some embodiments the sequences are substantially identical over the full length of the sequences being compared, such as the coding region of a target protein or an antibody. In some embodiments, identity exists over a region of the nucleotide sequences that is at least about 10 bases, at least about 20 bases, at least about 40-60 bases, at least about 60-80 bases in length or any integral value there between. In some embodiments, identity exists over a longer region than 60-80 bases, such as at least about 80-1000 bases or more, and in some embodiments the sequences are substantially identical over the full length of the sequences being compared, such as a nucleotide sequence encoding a protein of interest.

As used herein, the term “conjugate” refers to a complex formed by the covalent or non-covalent attachment of two or more distinct molecules or moieties. In some embodiments, the conjugate is formed by at least one molecule or moiety that possesses the ability to cross the BBB (e.g., an anti-CD98hc antibody disclosed herein) and another molecule or moiety (e.g., a drug, toxin, or imaging agent) that serves as an effector with therapeutic or diagnostic properties. This conjugation enables the combined entity to leverage the properties of each individual component to achieve a desired function, such as targeted delivery of a drug or imaging agent to the brain. In some embodiments, the two moieties are “linked” together, i.e., connected by covalent bond, such as peptide bond.

As used herein, the term “effector moiety” refers to the functional component of a conjugate molecule that is responsible for exerting the desired effect, such as the therapeutic or diagnostic effect. In some embodiments, the effector moiety can be a drug, toxin, enzyme, imaging agent, or other bioactive molecule that, when delivered to a specific target site within the body, performs its intended biological activity. The effector moiety can be therapeutic (e.g., chemotherapy drugs, neuroprotective agents) or diagnostic (e.g., contrast agents for imaging) .

A polypeptide, peptide, protein, antibody, polynucleotide, vector, cell, or composition which is “isolated” is a polypeptide, peptide, protein, antibody, polynucleotide, vector, cell, or composition which is in a form not found in nature. Isolated polypeptides, peptides, proteins, antibodies, polynucleotides, vectors, cells, or compositions include those which have been purified to a degree that they are no longer in a form in which they are found in nature. In some embodiments, a polypeptide, peptide, protein, antibody, polynucleotide, vector, cell, or composition which is isolated is substantially pure. In some embodiments, a material is “substantially pure” means that the material is at least 50%pure (i.e., free from contaminants) , at least 90%pure, at least 95%pure, at least 98%pure, or at least 99%pure.

The term “pharmaceutically acceptable carrier” or “pharmaceutically acceptable excipient” refers to a material that is suitable for drug administration to an individual along with an active agent without causing undesirable biological effects or interacting in a deleterious manner with any of the other components of the pharmaceutical composition. In some embodiments, the pharmaceutical compositions disclosed herein can comprise one or more of a buffer system, a preservative, a tonicity agent, a chelating agent, a stabilizer and/or a surfactant, as well as various combinations thereof. The use of preservatives, isotonic agents, chelating agents, stabilizers and surfactants in pharmaceutical compositions is well-known to the skilled person. Reference may be made to REMINGTON: THE SCIENCE AND PRACTICE OF PHARMACY, 19^th edition, 1995.

The term “treat” and its grammatical equivalents as used herein in connection with a disease or a condition, or a subject having a disease or a condition refer to an action that suppresses, eliminates, reduces, and/or ameliorates a symptom, the severity of the symptom, and/or the frequency of the symptom associated with the disease or disorder being treated.

The term “administer” and its grammatical equivalents as used herein refer to the act of delivering, or causing to be delivered, a therapeutic or a pharmaceutical composition to the body of a subject by a method described herein or otherwise known in the art. The therapeutic can be a compound, a polypeptide, an antibody, a cell, or a population of cells. Administering a therapeutic or a pharmaceutical composition includes prescribing a therapeutic or a pharmaceutical composition to be delivered into the body of a subject. Exemplary forms of administration include oral dosage forms, such as tablets, capsules, syrups, suspensions; injectable dosage forms, such as intravenous (IV) , intramuscular (IM) , or intraperitoneal (IP) ; transdermal dosage forms, including creams, jellies, powders, or patches; buccal dosage forms; inhalation powders, sprays, suspensions, and rectal suppositories.

The terms “effective amount, ” “therapeutically effective amount, ” and their grammatical equivalents as used herein refer to the administration of an agent to a subject, either alone or as a part of a pharmaceutical composition and either in a single dose or as part of a series of doses, in an amount that is capable of having any detectable, positive effect on any symptom, aspect, or characteristics of a disease, disorder or condition when administered to the subject. The therapeutically effective amount can be ascertained by measuring relevant physiological effects. The exact amount required varies from subject to subject, depending on the age, weight, and general condition of the subject, the severity of the condition being treated, the judgment of the clinician, and the like. An appropriate “effective amount” in any individual case can be determined by one of ordinary skill in the art using routine experimentation.

The term “subject” as used herein refers to any animal (e.g., a mammal) , including, but not limited to, humans, non-human primates, canines, felines, rodents, and the like, which is to be the recipient of a particular agent (e.g., therapeutic agent or diagnostic agent) . A subject can be a human. A subject can have a particular disease or condition. A subject can be at risk of having a particular disease or condition.

Ranges: throughout this disclosure, various aspects of the invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This applies regardless of the breadth of the range.

Exemplary genes and polypeptides are described herein with reference to GenBank numbers, GI numbers and/or SEQ ID NOS. It is understood that one skilled in the art can readily identify homologous sequences by reference to sequence sources, including but not limited to Uniprot (https: //www. uniprot. org/) , GenBank (ncbi. nlm. nih. gov/genbank/) and EMBL (embl. org/) .

The EU numbering is followed for numbering the amino acid residues in antibody sequences, specially in the variable regions of the immunoglobulins. Kabat et al. (1991) . SEQUENCES OF PROTEINS OF IMMUNOLOGICAL INTEREST (5TH ED. ) . U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health.
6.2 Antibodies targeting CD98hc

Provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98 heavy chain (CD98hc, e.g., human CD98hc) . In some embodiments, provided herein are anti-CD98hc antibodies. In some embodiments, the antibody is an IgA, IgD, IgE, IgG, or IgM antibody. In some embodiments, the antibody is an IgA antibody. In some embodiments, the antibody is an IgD antibody. In some embodiments, the antibody is an IgE antibody. In some embodiments, the antibody is an IgG antibody. In some embodiments, the antibody is an IgM antibody. In some embodiments, the antibodies provided herein can be an IgG1 antibody, an IgG2 antibody, an IgG3 antibody, or an IgG4 antibody. In some embodiments, the antibody is an IgG1 antibody. In some embodiments, the antibody is an IgG2 antibody. In some embodiments, the antibody is an IgG3 antibody. In some embodiments, the antibody is an IgG4 antibody.

In some embodiments, provided herein are antigen-binding fragments of an anti-CD98hc antibody. In some embodiments, antigen-binding fragments provided herein can be a single domain antibody (sdAb) , a heavy chain antibody (HCAb) , a Fab, a Fab’ , a F (ab’ ) ₂, a Fv, a single-chain variable fragment (scFv) , a disulfide-linked scFv [ (scFv) ₂] , or a diabody (dAb) . In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a single domain antibody (sdAb) . In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a heavy chain antibody (HCAb) . In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a Fab. In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a Fab’ . In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a F (ab’ ) ₂. In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a Fv. In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a scFv. In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a disulfide-linked scFv [ (scFv) ₂] . In some embodiments, the antigen-binding fragment of an anti-CD98hc antibody is a diabody (dAb) .

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise recombinant antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise monoclonal antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise polyclonal antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise camelid (e.g., camels, dromedary and llamas) antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise chimeric antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise humanized antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein comprise human antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein are humanized anti-CD98hc scFvs.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein are isolated. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein are substantially pure.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment provided herein comprises a multispecific antibody or antigen-binding fragment. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment provided herein comprises a bispecific antibody or antigen-binding fragment. In some embodiments, the bispecific antibody or antigen-binding fragment comprises an anti-CD98hc antibody or antigen-binding fragment provided herein. In some embodiments, the bispecific antibody or antigen-binding fragment comprises an anti-CD98hc scFv provided herein. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment provided herein comprises an internalizing antibody or antigen-binding fragment.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment provided herein comprises a monovalent antigen-binding site. In some embodiments, an anti-CD98hc antibody or antigen-binding fragment comprises a monospecific binding site. In some embodiments, an anti-CD98hc antibody or antigen-binding fragment comprises a bivalent binding site.

In some embodiments, an anti-CD98hc antibody or antigen-binding fragment is a monoclonal antibody or antigen-binding fragment. Monoclonal antibodies can be prepared by any method known to those of skill in the art. One exemplary approach is screening protein expression libraries, e.g., phage or ribosome display libraries. Phage display is described, for example, in Ladner et al., U.S. Patent No. 5,223,409; Smith (1985) Science 228: 1315-1317; and WO 92/18619. In some embodiments, recombinant monoclonal antibodies are isolated from phage display libraries expressing variable regions or CDRs of a desired species. Screening of phage libraries can be accomplished by various techniques known in the art.

In some embodiments, a monoclonal antibody is modified by using recombinant DNA technology to generate alternative antibodies. In some embodiments, the constant domains of the light chain and heavy chain of a mouse monoclonal antibody are replaced with the constant regions of a human antibody to generate a chimeric antibody. In some embodiments, the constant regions are truncated or removed to generate a desired antibody fragment of a monoclonal antibody. In some embodiments, site-directed or high-density mutagenesis of the variable region (s) is used to optimize specificity and/or affinity of a monoclonal antibody.

In some embodiments, provided herein is the anti-CD98hc antibody clone SIR-BP-H001-H010, i.e., SIR-BP-H001, SIR-BP-H002, SIR-BP-H003, SIR-BP-H004, SIR-BP-H005, SIR-BP-H006, SIR-BP-H007, SIR-BP-H008, SIR-BP-H009 and SIR-BP-H010. The sequence features are described below. The specific CDR sequences defined herein are generally based on Kabat definition. However, it is understood that a general reference to a heavy chain CDR or CDRs and/or a light chain CDR or CDRs of a specific antibody encompasses all CDR definitions as known to those of skill in the art. In some embodiments, provided herein are anti-CD98hc antibodies having the VH CDRs and/or VL CDRs of antibody clone SIR-BP-H001-H010 disclosed herein, wherein the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as exemplified in detail below) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H001. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H001 (SEQ ID NO: 5) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H001 (SEQ ID NO: 6) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H001. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H001 (SEQ ID NO: 5) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H001 (SEQ ID NO: 6) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H001, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H001. The SIR-BP-H001 variant can have a VH that is a variant of the VH of SIR-BP-H001 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 5. The SIR-BP-H001 variant can have a VH that is a variant of the VH of SIR-BP-H001 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 5. The SIR-BP-H001 variant can have a VL that is a variant of the VL of SIR-BP-H001 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 6. The SIR-BP-H001 variant can have a VL that is a variant of the VL of SIR-BP-H001 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 6. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H001 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H001 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H001. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H001.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a heavy chain variable region (VH) comprising one, two, and/or three heavy chain variable region CDRs (VH CDRs) from Table 1a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a light chain variable region (VL) comprising one, two, and/or three light chain variable region CDRs (VL CDRs) from Table 1a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 1a.

Table 1a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H001

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 25; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 26; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 27; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 28; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 29; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 30; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 25; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 26; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 27; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 25, 26 and 27, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 28; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 29; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 30; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 28, 29 and 30, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 25, 26, 27, 28, 29 and 30, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 1b Amino acid sequences of VH and VL of SIR-BP-H001

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 5; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 6. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 5 and 6, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 5. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 5. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 5. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 5. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 5. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 5.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 6. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 6. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 6. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 6. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 6. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 6.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H001. In some embodiments, provided herein are humanized SIR-BP-H001. In some embodiments, the SIR-BP-H001 variant can have a VH that is a variant of the VH of SIR-BP-H001 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 5. In some embodiments, the variant can have up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 5. In some embodiments, the variant can have up to about 3 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 5. In some embodiments, the SIR-BP-H001 variant can have a VL that is a variant of the VL of SIR-BP-H001 having about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 6. In some embodiments, the variant can have up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 6. In some embodiments, the variant can have up to about 3 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 6. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H001 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H001 has up to 3 conservative amino acid substitutions.

The anti-CD98hc antibodies or antigen-binding fragments thereof can comprise a combination of any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv. In some embodiments, the VH and VL are connected by a linker. In some embodiments, the anti-CD98hc scFv provided herein comprises (1) from N terminus to C terminus, the VH, a linker, and the VL; or (2) from N terminus to C terminus, the VL, a linker, and the VH. The linker can be a flexible linker or a rigid linker. In some embodiments, the linker has the amino acid sequence of (G4S) 3 (SEQ ID NO: 130) . In some embodiments, the linker has the amino acid sequence of GTEGKSSGSGSESKST (SEQ ID NO: 131) .

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 5 and/or a VL having the amino acid sequence of SEQ ID NO: 6. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 5 and 6, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H002. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H002 (SEQ ID NO: 7) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H002 (SEQ ID NO: 8) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H002. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H002 (SEQ ID NO: 7) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H002 (SEQ ID NO: 8) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H002, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H002. The SIR-BP-H002 variant can have a VH that is a variant of the VH of SIR-BP-H002 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 7. The SIR-BP-H002 variant can have a VH that is a variant of the VH of SIR-BP-H002 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 7. The SIR-BP-H002 variant can have a VL that is a variant of the VL of SIR-BP-H002 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 8. The SIR-BP-H002 variant can have a VL that is a variant of the VL of SIR-BP-H002 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 8. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H002 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H002 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H002. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H002.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 2a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 2a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 2a.

Table 2a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H002

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 31; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 32; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 33; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 34; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 35; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 36; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 31; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 32; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 33; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 31, 32 and 33, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 34; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 35; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 36; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 34, 35 and 36, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 31, 32, 33, 34, 35 and 36, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 2b Amino acid sequences of VH and VL of SIR-BP-H002

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 7; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 8. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 7 and 8, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 7. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 7. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 7. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 7. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 7. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 7.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 8. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 8. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 8. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 8. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 8. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 8.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 7 and/or a VL having the amino acid sequence of SEQ ID NO: 8. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 7 and 8, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H003. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H003 (SEQ ID NO: 9) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H003 (SEQ ID NO: 10) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H003. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H003 (SEQ ID NO: 9) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H003 (SEQ ID NO: 10) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H003, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H003. The SIR-BP-H003 variant can have a VH that is a variant of the VH of SIR-BP-H003 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 9. The SIR-BP-H003 variant can have a VH that is a variant of the VH of SIR-BP-H003 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 9. The SIR-BP-H003 variant can have a VL that is a variant of the VL of SIR-BP-H003 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 10. The SIR-BP-H003 variant can have a VL that is a variant of the VL of SIR-BP-H003 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 10. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H003 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H003 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H003. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H003.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 3a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 3a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 3a.

Table 3a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H003

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 37; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 38; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 39; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 40; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 41; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 42; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 37; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 38; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 39; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 37, 38 and 39, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 40; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 41; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 42; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 40, 41 and 42, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 37, 38, 39, 40, 41 and 42, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 3b Amino acid sequences of VH and VL of SIR-BP-H003

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 9; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 10. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 9 and 10, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 9. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 9. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 9. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 9. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 9. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 9.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 10. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 10. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 10. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 10. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 10. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 10.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 9 and/or a VL having the amino acid sequence of SEQ ID NO: 10. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 9 and 10, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H004. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H004 (SEQ ID NO: 11) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H004 (SEQ ID NO: 12) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H004. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H004 (SEQ ID NO: 11) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H004 (SEQ ID NO: 12) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H004, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H004. The SIR-BP-H004 variant can have a VH that is a variant of the VH of SIR-BP-H004 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 11. The SIR-BP-H004 variant can have a VH that is a variant of the VH of SIR-BP-H004 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 11. The SIR-BP-H004 variant can have a VL that is a variant of the VL of SIR-BP-H004 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 12. The SIR-BP-H004 variant can have a VL that is a variant of the VL of SIR-BP-H004 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 12. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H004 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H004 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H004. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H004.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 4a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 4a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 4a.

Table 4a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H004

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 43; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 44; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 45; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 46; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 47; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 48; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 43; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 44; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 45; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 43, 44 and 45, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 46; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 47; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 48; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 46, 47 and 48, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 43, 44, 45, 46, 47 and 48, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 4b Amino acid sequences of VH and VL of SIR-BP-H004

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 11; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 12. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 11 and 12, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 11. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 11. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 11. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 11. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 11. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 11.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 12. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 12. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 12. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 12. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 12. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 12.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 11 and/or a VL having the amino acid sequence of SEQ ID NO: 12. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 11 and 12, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H005. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H005 (SEQ ID NO: 13) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H005 (SEQ ID NO: 14) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H005. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H005 (SEQ ID NO: 13) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H005 (SEQ ID NO: 14) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H005, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H005. The SIR-BP-H005 variant can have a VH that is a variant of the VH of SIR-BP-H005 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 13. The SIR-BP-H005 variant can have a VH that is a variant of the VH of SIR-BP-H005 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 13. The SIR-BP-H005 variant can have a VL that is a variant of the VL of SIR-BP-H005 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 14. The SIR-BP-H005 variant can have a VL that is a variant of the VL of SIR-BP-H005 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 14. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H005 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H005 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H005. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H005.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 5a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 5a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 5a.

Table 5a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H005

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 49; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 50; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 51; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 52; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 53; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 54; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 49; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 50; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 51; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 49, 50 and 51, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, the VH CDR2 can have the amino acid sequence of SEQ ID NO: 50 with a substitution at G8 (which corresponds to G57 in the VH) . In some embodiments, the VH CDR2 can have the amino acid sequence of SEQ ID NO: 50 with a substitution of G8A. In some embodiments, the VH CDR2 has the amino acid sequence of SEQ ID NO: 118.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 52; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 53; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 54; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 52, 53 and 54, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of (1) SEQ ID NOs: 49, 50, 51, 52, 53 and 54, respectively, or (2) SEQ ID NOs: 49, 118, 51, 52, 53 and 54, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 5b Amino acid sequences of VH and VL of SIR-BP-H005 and the humanized VHs and VLs of SIR-BP-H005

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 13; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 14. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 13 and 14, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 13. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 13. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 13. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 13. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 13. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 13.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 14. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 14. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 14. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 14. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 14. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 14.

In some embodiments, provided herein are humanized SIR-BP-H005. In some embodiments, provided herein are humanized anti-CD98hc antibodies or antigen-binding fragments thereof comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110 and 137; and/or (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to SEQ ID NO: 103 or 105.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 102. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 102. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 102. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 102. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 102. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 102.

In some embodiments, the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 104. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 104. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 104. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 104. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 104. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 104.

In some embodiments, the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 106. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 106. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 106. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 106. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 106. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 106.

In some embodiments, the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 108. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 108. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 108. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 108. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 108. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 108.

In some embodiments, the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 110. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 110. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 110. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 110. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 110. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 110.

In some embodiments, the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 137. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 137. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 137. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 137. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 137. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 137.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 103. In some embodiments, the VL has at least 85%sequence identity to SEQ ID NO: 103. In some embodiments, the VL has at least 90%sequence identity to SEQ ID NO: 103. In some embodiments, the VL has at least 95%sequence identity to SEQ ID NO: 103. In some embodiments, the VL has at least 98%sequence identity to SEQ ID NO: 103. In some embodiments, the VL has the amino acid sequence of SEQ ID NO: 103.

In some embodiments, the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 105. In some embodiments, the VL has at least 85%sequence identity to SEQ ID NO: 105. In some embodiments, the VL has at least 90%sequence identity to SEQ ID NO: 105. In some embodiments, the VL has at least 95%sequence identity to SEQ ID NO: 105. In some embodiments, the VL has at least 98%sequence identity to SEQ ID NO: 105. In some embodiments, the VL has the amino acid sequence of SEQ ID NO: 105.

In some embodiments, provided herein are anti-CD98hc antibodies or antigen-binding fragments thereof that comprise VH CDRs from a VH described herein (SEQ ID NO: 13, 102, 104, 106, 108, 110 or 137) , and/or VL CDRs from a VL described herein (SEQ ID NO: 14, 103, or 105) . Methods to identify CDRs are well known in the art. For example, software programs (abYsis) on publicly available websites are known to those of skill in the art for analysis of antibody sequence and determination of CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising (a) a VH comprising VH CDRs 1, 2, and 3 from a VH having an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110 and 137; and/or (b) a VL comprising VL CDRs 1, 2, and 3 from a VL having the amino acid sequence of SEQ ID NO: 103 or 105.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of a humanized SIR-BP-H005 provided herein. The variant can have a VH that is a variant of the VH of a humanized SIR-BP-H005 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110 and 137. The variant can have a VH that is a variant of the VH of a humanized SIR-BP-H005 having up to about 5 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110 and 137. The variant can have a VL that is a variant of the VL of a humanized SIR-BP-H005 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 103 or 105. The variant can have a VL that is a variant of the VL of a humanized SIR-BP-H005 having up to about 5 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 103 or 105. In some embodiments, the variant of a humanized SIR-BP-H005 has up to about 5 conservative amino acid substitutions.

In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 102 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 102 and 105, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 104 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 104 and 105, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 106 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 106 and 105, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 108 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 108 and 105, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 110 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 110 and 105, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 137 and 103, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 137 and 105, respectively.

Table 5c Amino acid sequences of SIR-BP-H005 scFv

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises (1) a VH selected from the group consisting of SEQ ID NOs: 13, 102, 104, 106, 108, 110, and 137, and/or (2) a VL having the amino acid sequence of SEQ ID NO: 103 or 105. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of (1) SEQ ID NOs: 13 and 14, respectively; (2) SEQ ID NOs: 102 and 103, respectively; (3) SEQ ID NOs: 102 and 105, respectively; (4) SEQ ID NOs: 104 and 103, respectively; (5) SEQ ID NOs: 104 and 105, respectively; (6) SEQ ID NOs: 106 and 103, respectively; (7) SEQ ID NOs: 106 and 105, respectively; (8) SEQ ID NOs: 108 and 103, respectively; (9) SEQ ID NOs: 108 and 105, respectively; (10) SEQ ID NOs: 110 and 103, respectively; (11) SEQ ID NOs: 110 and 105, respectively; (12) SEQ ID NOs: 137 and 103, respectively; or (13) SEQ ID NOs: 137 and 105, respectively.

In some embodiments, provided herein are anti-CD98hc scFv having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-97 and
138. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at
least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 92. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 92. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 93. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 93. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 94. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 94. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 95. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 95. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 96. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 96. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 97. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 97. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 138. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 138.

In some embodiments, the anti-CD98hc scFv provided herein is a variant of a SIR-BP-H005 scFv provided herein. In some embodiments, the anti-CD98hc scFv provided herein is a variant of HZ01, HZ02, HZ03, HZ04, HZ05, or HZ09. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 92. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 93. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 94. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 95. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 96. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 97. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 138. The variant can have up to about 5 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-97 and 138. In some embodiments, the variant can have up to about 5 conservative amino acid substitutions.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H006. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H006 (SEQ ID NO: 15) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H006 (SEQ ID NO: 16) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H006. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H006 (SEQ ID NO: 15) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H006 (SEQ ID NO: 16) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H006, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H006. The SIR-BP-H006 variant can have a VH that is a variant of the VH of SIR-BP-H006 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 15. The SIR-BP-H006 variant can have a VH that is a variant of the VH of SIR-BP-H006 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 15. The SIR-BP-H006 variant can have a VL that is a variant of the VL of SIR-BP-H006 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 16. The SIR-BP-H006 variant can have a VL that is a variant of the VL of SIR-BP-H006 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 16. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H006 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H006 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H006. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H006.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 6a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 6a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 6a.

Table 6a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H006

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 55; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 56; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 57; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 58; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 59; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 60; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 55; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 56; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 57; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 55, 56 and 57, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 58; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 59; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 60; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 58, 59 and 60, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 55, 56, 57, 58, 59 and 60, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 6b Amino acid sequences of VH and VL of SIR-BP-H006

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 15; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 16. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 15 and 16, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 15. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 15. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 15. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 15. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 15. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 15.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 16. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 16. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 16. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 16. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 16. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 16.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 15 and/or a VL having the amino acid sequence of SEQ ID NO: 16. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 15 and 16, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H007. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H007 (SEQ ID NO: 17) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H007 (SEQ ID NO: 18) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H007. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H007 (SEQ ID NO: 17) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H007 (SEQ ID NO: 18) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H007, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H007. The SIR-BP-H007 variant can have a VH that is a variant of the VH of SIR-BP-H007 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 17. The SIR-BP-H007 variant can have a VH that is a variant of the VH of SIR-BP-H007 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 17. The SIR-BP-H007 variant can have a VL that is a variant of the VL of SIR-BP-H007 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 18. The SIR-BP-H007 variant can have a VL that is a variant of the VL of SIR-BP-H007 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 18. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H007 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H007 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H007. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H007.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 7a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 7a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 7a.

Table 7a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H007

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 61; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 62; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 63; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 64; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 65; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 66; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 61; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 62; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 63; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 61, 62 and 63, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 64; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 65; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 66; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 64, 65 and 66, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 61, 62, 63, 64, 65 and 66, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 7b Amino acid sequences of VH and VL of SIR-BP-H007

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 17; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 18. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 17 and 18, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 17. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 17. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 17. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 17. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 17. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 17.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 18. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 18. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 18. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 18. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 18. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 18.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 17 and/or a VL having the amino acid sequence of SEQ ID NO: 18. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 17 and 18, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H008. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H008 (SEQ ID NO: 19) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H008 (SEQ ID NO: 20) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H008. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H008 (SEQ ID NO: 19) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H008 (SEQ ID NO: 20) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H008, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H008. The SIR-BP-H008 variant can have a VH that is a variant of the VH of SIR-BP-H008 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 19. The SIR-BP-H008 variant can have a VH that is a variant of the VH of SIR-BP-H008 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 19. The SIR-BP-H008 variant can have a VL that is a variant of the VL of SIR-BP-H008 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 20. The SIR-BP-H008 variant can have a VL that is a variant of the VL of SIR-BP-H008 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 20. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H008 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H008 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H008. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H008.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 8a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 8a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 8a.

Table 8a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H008

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 67; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 68; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 69; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 70; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 71; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 72; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 67; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 68; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 69; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 67, 68 and 69, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 70; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 71; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 72; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 70, 71 and 72, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 67, 68, 69, 70, 71 and 72, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. . In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 8b Amino acid sequences of VH and VL of SIR-BP-H008

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 19; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 20. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 19 and 20, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 19. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 19. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 19. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 19. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 19. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 19.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 20. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 20. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 20. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 20. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 20. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 20.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 19 and/or a VL having the amino acid sequence of SEQ ID NO: 20. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 19 and 20, respectively.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H009. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H009 (SEQ ID NO: 21) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H009 (SEQ ID NO: 22) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H009. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H009 (SEQ ID NO: 21) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H009 (SEQ ID NO: 22) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H009, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H009. The SIR-BP-H009 variant can have a VH that is a variant of the VH of SIR-BP-H009 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 21. The SIR-BP-H009 variant can have a VH that is a variant of the VH of SIR-BP-H009 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 21. The SIR-BP-H009 variant can have a VL that is a variant of the VL of SIR-BP-H009 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 22. The SIR-BP-H009 variant can have a VL that is a variant of the VL of SIR-BP-H009 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 22. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H009 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H009 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H009. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H009.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 9a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 9a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 9a.

Table 9a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H009

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 73; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 74; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 75; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 76; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 77; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 78; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 73; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 74; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 75; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 73, 74 and 75, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, the VH CDR3 can have the amino acid sequence of SEQ ID NO: 75 with a substitution at G2 (which corresponds to G102 in the VH) . In some embodiments, the VH CDR3 can have the amino acid sequence of SEQ ID NO: 75 with a substitution of G2A. In some embodiments, the VH CDR3 can have the amino acid sequence of SEQ ID NO: 119.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 76; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 77; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 78; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 76, 77 and 78, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of (1) SEQ ID NOs: 73, 74, 75, 76, 77 and 78, respectively, or (2) SEQ ID NOs: 73, 74, 119, 76, 77 and 78, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 9b Amino acid sequences of VH and VL of SIR-BP-H009 and the humanized VHs and VLs of SIR-BP-H009

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 21; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 22. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 21 and 22, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 21. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 21. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 21. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 21. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 21. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 21.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 22. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 22. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 22. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 22. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 22. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 22.

In some embodiments, provided herein are humanized SIR-BP-H009. In some embodiments, provided herein are humanized anti-CD98hc antibodies or antigen-binding fragments thereof comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116; and/or (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to SEQ ID NO: 113.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 112. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 112. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 112. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 112. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 112. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 112.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 114. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 114. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 114. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 114. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 114. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 114.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 116. In some embodiments, the VH has at least 85%sequence identity to SEQ ID NO: 116. In some embodiments, the VH has at least 90%sequence identity to SEQ ID NO: 116. In some embodiments, the VH has at least 95%sequence identity to SEQ ID NO: 116. In some embodiments, the VH has at least 98%sequence identity to SEQ ID NO: 116. In some embodiments, the VH has the amino acid sequence of SEQ ID NO: 116.

In some embodiments, provided herein are humanized antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 113. In some embodiments, the VL has at least 85%sequence identity to SEQ ID NO: 113. In some embodiments, the VL has at least 90%sequence identity to SEQ ID NO: 113. In some embodiments, the VL has at least 95%sequence identity to SEQ ID NO: 113. In some embodiments, the VL has at least 98%sequence identity to SEQ ID NO: 113. In some embodiments, the VL has the amino acid sequence of SEQ ID NO: 113.

In some embodiments, provided herein are anti-CD98hc antibodies or antigen-binding fragments thereof that comprise VH CDRs from a VH described herein (SEQ ID NO: 21, 112, 114, or 116) , and/or VL CDRs from a VL described herein (SEQ ID NO: 22 or 113) . Methods to identify CDRs are well known in the art. For example, software programs (abYsis) on publicly available websites are known to those of skill in the art for analysis of antibody sequence and determination of CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising (a) a VH comprising VH CDRs 1, 2, and 3 from a VH having an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116; and/or (b) a VL comprising VL CDRs 1, 2, and 3 from a VL having the amino acid sequence of SEQ ID NO: 113.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of a humanized SIR-BP-H009 provided herein. The variant can have a VH that is a variant of the VH of a humanized SIR-BP-H009 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116. The variant can have a VH that is a variant of the VH of a humanized SIR-BP-H009 having up to about 5 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116. The variant can have a VL that is a variant of the VL of a humanized SIR-BP-H009 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 113. The variant can have a VL that is a variant of the VL of a humanized SIR-BP-H009 having up to about 5 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 113. In some embodiments, the variant of a humanized SIR-BP-H009 has up to about 5 conservative amino acid substitutions.

In some embodiments, provided herein are anti-CD98hc antibodies or antigen-binding fragments thereof comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 21 and 22, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 112 and 113, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 114 and 113, respectively. In some embodiments, the VH and VL have the amino acid sequences of SEQ ID NOs: 116 and 113, respectively.

Table 9c Amino acid sequences of SIR-BP-H009 scFv

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFv comprises (1) a VH having an amino acid sequence selected from the group consisting of SEQ ID NOs: 21, 112, 114, and 116, and/or (2) a VL having the amino acid sequence of SEQ ID NO: 22 or 113. In some embodiments, the anti-CD98hc scFv comprises a VH and a VL having the amino acid sequences of (1) SEQ ID NOs: 21 and 22, respectively; (2) SEQ ID NOs: 112 and 113, respectively; (3) SEQ ID NOs: 114 and 113, respectively; (4) SEQ ID NOs: 116 and 113, respectively.

In some embodiments, provided herein are anti-CD98hc scFv having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 98-101. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 98. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 98. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 99. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 99. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 100. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 100. In some embodiments, the anti-CD98hc scFv has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 101. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 101.

In some embodiments, the anti-CD98hc scFv provided herein is a variant of a SIR-BP-H009 scFv provided herein. In some embodiments, the anti-CD98hc scFv provided herein is a variant of HZ06, HZ07, or HZ08. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 98. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 99. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 100. The variant can have up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the amino acid sequence of SEQ ID NO: 101. The variant can have up to about 5 amino acid substitutions, additions, and/or deletions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 98-101. The variant can have up to about 5 conservative amino acid substitutions in an amino acid sequence selected from the group consisting of SEQ ID NOs: 98-101.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is the antibody designated as SIR-BP-H010. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH from SIR-BP-H010 (SEQ ID NO: 23) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL from SIR-BP-H010 (SEQ ID NO: 24) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have both the VH and the VL from SIR-BP-H010. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VH that comprises VH CDRs 1, 2, and 3 from the VH from SIR-BP-H010 (SEQ ID NO: 23) . In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein has a VL that comprises VL CDRs 1, 2, and 3 from the VL from SIR-BP-H010 (SEQ ID NO: 24) . The anti-CD98hc antibody or antigen-binding fragment thereof provided herein can have a VH comprising VH CDRs 1, 2, and 3 and a VL comprising VL CDRs 1, 2, and 3 from the VH and VL of SIR-BP-H010, respectively. The CDRs can be defined by any system known in the art. In some embodiments, the CDRs are defined by Kabat, Chothia, IMGT, AbM, or Contact. In some embodiments, the CDRs are defined by Kabat (as detailed herein) . In some embodiments, the CDRs are defined by Chothia. In some embodiments, the CDRs are defined by IMGT. In some embodiments, the CDRs are defined by AbM. In some embodiments, the CDRs are defined by Contact.

In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a variant of SIR-BP-H010. The SIR-BP-H010 variant can have a VH that is a variant of the VH of SIR-BP-H010 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 23. The SIR-BP-H010 variant can have a VH that is a variant of the VH of SIR-BP-H010 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 23. The SIR-BP-H010 variant can have a VL that is a variant of the VL of SIR-BP-H010 having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 24. The SIR-BP-H010 variant can have a VL that is a variant of the VL of SIR-BP-H010 having up to about 5 amino acid substitutions, additions, and/or deletions in SEQ ID NO: 24. The amino acid substitutions, additions, and/or deletions can be in the VH CDRs or VL CDRs. In some embodiments, the amino acid substitutions, additions, and/or deletions are not in the CDRs. In some embodiments, the variant of SIR-BP-H010 has up to about 5 conservative amino acid substitutions. In some embodiments, the variant of SIR-BP-H010 has up to 3 conservative amino acid substitutions. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a humanized antibody or antigen-binding fragment derived from SIR-BP-H010. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof provided herein is a human antibody or antigen-binding fragment derived from SIR-BP-H010.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, three, four, five, and/or six CDRs of any one of the antibodies described herein. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VH comprising one, two, and/or three VH CDRs from Table 10a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise a VL comprising one, two, and/or three VL CDRs from Table 10a. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments provided herein comprise one, two, and/or three VH CDRs and one, two, and/or three VL CDRs from Table 10a.

Table 10a Amino acid sequences of VH CDRs and VL CDRs of SIR-BP-H010

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 79; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 80; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 81; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs; and/or a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 82; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 83; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 84; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH comprising (1) a VH CDR1 having the amino acid sequence of SEQ ID NO: 79; (2) a VH CDR2 having the amino acid sequence of SEQ ID NO: 80; and/or (3) a VH CDR3 having the amino acid sequence of SEQ ID NO: 81; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VH, wherein the VH comprises VH CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 79, 80 and 81, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VH CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VH CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VH CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc, comprising a VL comprising (1) a VL CDR1 having the amino acid sequence of SEQ ID NO: 82; (2) a VL CDR2 having the amino acid sequence of SEQ ID NO: 83; and/or (3) a VL CDR3 having the amino acid sequence of SEQ ID NO: 84; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc having a VL, wherein the VL comprises VL CDR1, CDR2 and CDR3 having the amino acid sequences of SEQ ID NOs: 82, 83 and 84, respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the VL CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the VL CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the VL CDRs.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2 and VL CDR3, having the amino acid sequences of SEQ ID NOs: 79, 80, 81, 82, 83 and 84, respectively, or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 3 amino acid substitutions, additions, and/or deletions in the CDRs. In some embodiments, the variant has up to about 5 conservative amino acid substitutions in the CDRs. In some embodiments, the variant has up to about 3 conservative amino acid substitutions in the CDRs.

Table 10b Amino acid sequences of VH and VL of SIR-BP-H010

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising: (a) a VH having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 23; and (b) a VL having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 24. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH and a VL, wherein the VH and VL have the amino acid sequences of SEQ ID NOs: 23 and 24, respectively.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH, wherein the VH has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 23. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 85%sequence identity to SEQ ID NO: 23. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 90%sequence identity to SEQ ID NO: 23. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 95%sequence identity to SEQ ID NO: 23. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VH having at least 98%sequence identity to SEQ ID NO: 23. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VH having the amino acid sequence of SEQ ID NO: 23.

In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL, wherein the VL has at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%sequence identity to SEQ ID NO: 24. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 85%sequence identity to SEQ ID NO: 24. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 90%sequence identity to SEQ ID NO: 24. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 95%sequence identity to SEQ ID NO: 24. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment thereof has a VL having at least 98%sequence identity to SEQ ID NO: 24. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind CD98hc comprising a VL having the amino acid sequence of SEQ ID NO: 24.

In some embodiments, the anti-CD98hc antigen-binding fragment provided herein is an scFv, comprising any VH disclosed herein and any VL disclosed herein. In some embodiments, the anti-CD98hc scFV comprises a VH having the amino acid sequence of SEQ ID NO: 23 and/or a VL having the amino acid sequence of SEQ ID NO: 24. In some embodiments, the anti-CD98hc scFV comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 23 and 24, respectively.

In some embodiments, provided herein are also antibodies or antigen-binding fragments that compete with the antibody or antigen-binding fragment provided above for binding to CD98hc (e.g., human CD98hc) . Antibodies that “compete with another antibody for binding to a target” refer to antibodies that inhibit (partially or completely) the binding of the other antibody to the target. Whether two antibodies compete with each other for binding to a target, i.e., whether and to what extent one antibody inhibits the binding of the other antibody to a target, can be determined using known competition experiments, e.g., surface plasmon resonance (SPR) analysis. In some embodiments, an anti-CD98hc antibody or antigen-binding fragment competes with, and inhibits binding of another antibody or antigen-binding fragment to CD98hc by at least 50%, 60%, 70%, 80%, 90%or 100%. Competition assays can be conducted as described, for example, in Ed Harlow and David Lane, Cold Spring Harb Protoc; 2006; doi: l0. H0l/pdb. prot4277 or in Chapter 11 of “Using Antibodies” by Ed Harlow and David Lane, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, USA 1999.

The present disclosure further contemplates additional variants and equivalents that are substantially homologous to the recombinant, monoclonal, chimeric, humanized, and human antibodies, or antibody fragments thereof, described herein. In some embodiments, it is desirable to improve the binding affinity of the antibody. In some embodiments, it is desirable to modulate biological properties of the antibody, including but not limited to, specificity, thermostability, expression level, effector function (s) , glycosylation, immunogenicity, and/or solubility. Those skilled in the art will appreciate that amino acid changes may alter post-translational processes of an antibody, such as changing the number or position of glycosylation sites or altering membrane anchoring characteristics.

Antibodies comprising functional variants of the heavy chain, light chains, VL regions, VH regions, or one or more CDRs of the antibodies of the examples as also provided herein. A functional variant of a heavy chain, a light chain, VL, VH, or CDRs used in the context of an antibody still allows the antibody to retain at least a substantial proportion (at least about 90%, 95%or more) of functional features of the “reference” and/or “parent” antibody, including affinity and/or the specificity/selectivity, Fc inertness and PK parameters such as half-life, Tmax, Cmax. Such functional variants typically retain significant sequence identity to the parent antibody and/or have substantially similar length of heavy and light chains. Exemplary variants include those which differ from heavy and/or light chains, VH and/or VL, and/or CDR regions of the parent antibody sequences mainly by conservative substitutions, e.g., 10, such as 9, 8, 7, 6, 5, 4, 3, 2 or 1 of the substitutions in the variant cam be conservative amino acid residue replacements.

Variations can be a substitution, deletion, or insertion of one or more nucleotides encoding the antibody or polypeptide that results in a change in the amino acid sequence as compared with the native antibody or polypeptide sequence. In some embodiments, amino acid substitutions are the result of replacing one amino acid with another amino acid having similar structural and/or chemical properties, such as the replacement of a leucine with a serine, e.g., conservative amino acid replacements. Insertions or deletions can be in the range of about 1 to 5 amino acids. In some embodiments, the substitution, deletion, or insertion includes less than 25 amino acid substitutions, less than 20 amino acid substitutions, less than 15 amino acid substitutions, less than 10 amino acid substitutions, less than 5 amino acid substitutions, less than 4 amino acid substitutions, less than 3 amino acid substitutions, or less than 2 amino acid substitutions relative to the parent molecule. In some embodiments, variations in the amino acid sequence that are biologically useful and/or relevant can be determined by systematically making insertions, deletions, or substitutions in the sequence and testing the resulting variant proteins for activity as compared to the parent protein.

In some embodiments, provided herein are variants of anti-CD98hc antibodies or antigen-binding fragments described herein. In some embodiments, a variant comprises one to 30 amino acid substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to 25 amino acid substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to 20 substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to 15 substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to 10 substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to five amino acid substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, a variant comprises one to three amino acid substitutions, additions, and/or deletions in the parent antibody or antigen-binding fragment. In some embodiments, the amino acid substitution (s) is in a CDR of the antibody or antigen-binding fragment. In some embodiments, the amino acid substitution (s) is not in a CDR of the antibody or antigen-binding fragment. In some embodiments, the amino acid substitution (s) is in a framework region of the antibody or antigen-binding fragment. In some embodiments, the amino acid substitutions, additions, and/or deletions are conservative amino acid substitutions.

The variant antibodies or antigen-binding fragments described herein can be generated using methods known in the art, including but not limited to, site-directed mutagenesis, alanine scanning mutagenesis, and PCR mutagenesis. Methods for mutagenesis and nucleotide sequence alterations are well known in the art. See, for example, Walker and Gaastra, eds. (1983) TECHNIQUES IN MOLECULAR BIOLOGY (MacMillan Publishing Company, New York) ; Kunkel, Proc. Natl. Acad. Sci. USA 82: 488-492 (1985) ; Kunkel et al., Methods Enzymol. 54: 367-382 (1987) ; Sambrook et al. (1989) MOLECULAR CLONING: A LABORATORY MANUAL (Cold Spring Harbor, N.Y. ) ; U.S. Pat. No. 4,873,192; and the references cited therein; herein incorporated by reference. Guidance as to appropriate amino acid substitutions that do not affect biological activity of the polypeptide of interest can be found in the model of Dayhoff et al. (1978) in Atlas of Protein Sequence and Structure (Natl. Biomed. Res. Found., Washington, D.C. ) , pp. 345-352, herein incorporated by reference in its entirety. The model of Dayhoff et al. uses the Point Accepted Mutation (PAM) amino acid similarity matrix (PAM 250 matrix) to determine suitable conservative amino acid substitutions. Conservative substitutions, such as exchanging one amino acid with another having similar properties, can be beneficial.

In some embodiments, variants can include addition of amino acid residues at the amino-and/or carboxyl-terminal end of the antibody or polypeptide. The length of additional amino acids residues can range from one residue to a hundred or more residues. In some embodiments, a variant comprises an N-terminal methionyl residue. In some embodiments, the variant comprises an additional polypeptide/protein (e.g., Fc region) to create a fusion protein. In some embodiments, a variant is engineered to be detectable and can comprise a detectable label and/or protein (e.g., a fluorescent tag or an enzyme) .

In some embodiments, bispecific antibodies disclosed herein can be chemically modified naturally or by intervention. In some embodiments, the bispecific antibodies are chemically modified by glycosylation, acetylation, pegylation, phosphorylation, amidation, derivatization by known protecting/blocking groups, proteolytic cleavage, and/or linkage to a cellular ligand or other protein. Any of numerous chemical modifications can be carried out by known techniques. The bispecific antibodies provided herein can comprise one or more analogs of an amino acid (including, for example, unnatural amino acids) , as well as other modifications known in the art.

In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with an anti-CD98hc antibody or antigen-binding fragment disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H001 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H001 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H002 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H002 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H003 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H003 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H004 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H004 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H005 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H005 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H006 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H006 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H007 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H007 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H008 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H008 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H009 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H009 disclosed herein for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with chimeric SIR-BP-H010 for binding to CD98hc (e.g., human CD98hc) . In some embodiments, provided herein are antibodies or antigen-binding fragments that compete with a humanized SIR-BP-H010 disclosed herein for binding to CD98hc (e.g., human CD98hc) .

Epitope mapping is a method of identifying the binding site, region, or epitope on a target protein where an antibody binds. A variety of methods are known in the art for mapping epitopes on target proteins. These methods include mutagenesis, including but not limited to, shotgun mutagenesis, site-directed mutagenesis, and alanine scanning; domain or fragment scanning; peptide scanning (e.g., Pepscan technology) ; display methods (e.g., phage display, microbial display, and ribosome/mRNA display) ; methods involving proteolysis and mass spectroscopy; and structural determination (e.g., X-ray crystallography and NMR) . In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein are characterized by assays including, but not limited to, N-terminal sequencing, amino acid analysis, HPLC, mass spectrometry, ion exchange chromatography, and papain digestion.

The anti-CD98hc antibodies or antigen-binding fragments of the present disclosure can be analyzed for their physical, chemical and/or biological properties by various methods known in the art. In some embodiments, an anti-CD98hc antibody is tested for its ability to bind CD98hc (e.g., human CD98hc or cyno CD98hc) . Binding assays include, but are not limited to, BLI, SPR (e.g., Biacore) , ELISA, and FACS. In addition, antibodies can be evaluated for solubility, stability, thermostability, viscosity, expression levels, expression quality, and/or purification efficiency.

In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with high affinity, for example, with a K_D of 10^-7 M or less, 5×10^-8 M or less, 10^-8 M or less, 5×10^-9 M or less, 10^-9 M or less, 5×10^-10 M or less, or 10^-10 M or less. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with high affinity, for example, with a K_D of about 10^-7 M, about 5×10^-8 M, about 10^-8 M, about 5×10^-9 M, about 10^-9 M, about 5×10^-10 M, or about 10^-10 M. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with a K_D of about 10^-7 M. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with a K_D of about 10^-8 M. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with a K_D of about 10^-9 M. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with a K_D ranging from 10^-10 M to 10^-7 M, from 10^-9 M to 10^-7 M, from 10^-8 M to 10^-7 M, from 10^-10 M to 5×10^-8 M, from 10^-9 M to 5×10^-8 M, from 10^-8 M to 5×10^-8 M, from 10^-10 M to 10^-8 M, from 10^-9 M to 10^-8 M, from 10^-10 M to 5×10^-9 M, from 10^-9 M to 5×10^-9 M, or from 10^-10 M to 10^-9 M. In some embodiments, anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc with high affinity, for example, with a K_D from 10^-9 M to 10^-7 M. In some embodiments, the K_D is determined by BLI. In some embodiments, the K_D is determined by SPR.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein bind to both human CD98hc and cynomolgus CD98hc. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein bind to human CD98hc but not cynomolgus CD98hc.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein can cross the BBB.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein are internalizing antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments disclosed herein can be internalized in BBB epithelial cells greater than 10-fold as compared to internalization by an isotype control.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulate at least 2-fold more than an isotype control in the brain. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulates at least 3, at least 4, or at least 5-fold more than an isotype control in the brain. In some embodiments, the accumulation is measured in a hCD98 knock-in mouse.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulate at least 2-fold more than an isotype control in the brain parenchyma. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulate at least 3, at least 4, or at least 5-fold more than an isotype control in the brain parenchyma. In some embodiments, the accumulation is measured in a hCD98 knock-in mouse.

In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein do not affect BBB integrity or function. Leucine transported into the brain parenchyma serves several functions, including but not limited to, providing a metabolic precursor of fuel molecules, participating in the maintenance of the nitrogen balance, and regulating the activity of some enzymes important for brain energy metabolism. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments described herein do not affect leucine uptake by CD98-expressing cells.
6.3 Conjugates

Provided herein are conjugates comprising an antibody or antigen-binding fragment disclosed herein that specifically binds to human CD98hc. Conjugates provided herein comprise the anti-CD98hc antibody or antigen-binding fragment and an effector moiety. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment and the effector moiety form a complex by non-covalent interaction. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment is linked to the effector moiety.

By being conjugated to the anti-CD98hc antibody or antigen-binding fragment, the effector moiety can cross the BBB and be delivered to the CNS, such as the brain. In some embodiments, the effector moiety is selected from the group consisting of drugs for neurological diseases or disorders, neurotrophic factors, growth factors, enzymes, cytotoxic agents and imaging agents. In some embodiments, the effector moiety is a therapeutic agent, such as a small molecule drug or a biologic drug. In some embodiments, the effector moiety is a small molecule drug for neurological condition (e.g., temozolomide) . In some embodiments, the effector moiety is a peptide (e.g., an IGF-1 peptide) . In some embodiments, the effector moiety is an antibody (e.g., aducanumab) . In some embodiments, the effector moiety can be a gene therapy vector, such as a viral vector. In some embodiments, the effector moiety can be a neuroprotective agent, such as an antioxidant (e.g., Coenzyme Q10) or an anti-inflammatory agent (e.g., minocycline) .

In some embodiments, the effector moiety is a diagnostic agent, such as an imaging agent that helps visualize brain structure or pathology. The imaging agent can be a radioactive isotope, a contrast agent, or a fluorescent dye. In some embodiments, the imaging agent can be fluorodeoxyglucose (FDG) . In some embodiments, the imaging agent can be MRI contrast agent such as gadolinium-based agents.

In some embodiments, the effector moiety is a peptide. In some embodiments, provided herein are fusion proteins comprising the anti-CD98hc antibody or antigen-binding fragment and the peptide effector moiety, connected by a linker, such as a peptide linker. The linker can be e.g., a glycine linker, a glycine-rich linker, or a glycine-serine linker. The linker can be, for example, 1 to 20 amino acids in length. The linker can comprise the amino acid sequence (GGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 128) . The linker can comprise the amino acid sequence (GGGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 129) . The linker can comprise the amino acid sequence (GGGGS) 3 (SEQ ID NO: 130) . The linker can comprise the amino acid sequence GTEGKSSGSGSESKST (SEQ ID NO: 131) . The linker can comprise the amino acid sequence GGAGGA (SEQ ID NO: 132) . A person of ordinary skill in the art would understand that the fusion proteins disclosed herein are not limited by the specific linkers exemplified herein. Any peptide linker with the appropriate length and flexibility that allows both the anti-CD98hc and the peptide effector moiety to properly function can be used.

In some embodiments, a fusion protein provided herein comprises an anti-CD98hc antibody or antigen-binding fragment and a peptide effector moiety. In some embodiments, the peptide effector moiety is a peptide useful in protein replacement therapy (PRT) . In some embodiments, the peptide effector moiety is an enzyme (e.g., an enzyme for use in enzyme replacement therapy (ERT) ) or a catalytically active fragment thereof. In some embodiments, the peptide effector moiety is a growth factor. In some embodiments, the peptide effector moiety is a decoy receptor. In some embodiments, the peptide effector moiety is progranulin (PGRN) , prosaposin (PSAP) , or survival motor neuron protein (SMN) . In some embodiments, the peptide effector moiety can be an enzyme that is ubiquitin protein ligase E3A (UBE3A) , α-L-Iduronidase (IDUA) , Iduronate-2-sulphatase (IDS) , N-acetylgalactosamine-6-sulphatase (GALNS) , N-sulfoglucosamine sulfohydrolase (SGSH) , N-acetylgalactosamine-4-sulphatase (arylsulfatase B; ARSB) , acid sphingomyelinase (ASM) , β-glucocerebrosidase (GCase or GBA) , galactosylceramide beta-galactosidase, glucosylceramidase, beta-hexosaminidase A, beta-hexosaminidase B, arylsulfatase A, beta-galactosidase, acid ceramidase, alpha-glucosidase, lysosomal acid lipase, lysosomal protease, or a synthetic enzyme replacement thereof, such as laronidase, idursulfase, elosulfase alpha, or galsulfase, or a variant thereof, or a catalytically active fragment thereof. In some embodiments, the peptide effector moiety can be clusterin (APOJ) , Reelin, Tripeptidyl Peptidase 1 (CLN2/TPP1) , glucosamine (N-acetyl) -6-sulfatase (GNS) , heparan-α-glucosaminide N-acetyltransferase (HGSNAT) , or N-acetyl-α-glucosaminidase (NAGLU) .

In some embodiments, the fusion protein comprises an anti-CD98hc antibody or antigen-binding fragment and a peptide effector moiety, and an Fc portion. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment and the peptide effector moiety or polypeptide are linked to the N-terminus of the Fc portion of the fusion protein. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment is linked to the N-terminus of the Fc portion and the peptide effector moiety is linked to the C-terminus of the Fc portion of the fusion protein. In some embodiments, the anti-CD98hc antibody or antigen-binding fragment is linked to the C-terminus of the Fc portion and the peptide effector moiety is linked to the N-terminus of the Fc portion of the fusion protein.

In some embodiments, provided herein are fusion proteins comprising anti-CD98hc antibody or antigen-binding fragment linked to a second antibody or antigen-binding fragment. In some embodiments, the fusion protein is a multispecific antibody. In some embodiments, the fusion protein is a bispecific antibody. In some embodiments, the second antibody or antigen specifically binds to a CNS antigen. In some embodiments, the second antibody or antigen specifically binds to a brain antigen.

In some embodiments, the CNS antigen is selected from the group consisting of alpha-synuclein, amyloid precursor protein (APP) , amyloid-beta (Aβ) , apolipoprotein E (ApoE) , apolipoprotein E4 (ApoE4) , ATP-binding cassette sub-family A member 1 (ABCA1) , ATP-binding cassette sub-family A member 7 (ABCA7) , beta-secretase 1 (BACE1) , caspase 6, CD20, CD33 (Siglec3) , death receptor 6 (DR6) , disialoganglioside (GD2) , epidermal growth factor (EGF) , epidermal growth factor receptor (EGFR) , epidermal growth factor receptor 2 (EGFR2/HER2) , gamma secretase, glycoprotein nonmetastatic melanoma protein B (GPNMB) , GLP-1, HLA-DR1, HLA-DR5, huntingtin, IL-34, IL1RAP, interleukin-13 receptor alpha 2 (IL-13Rα2) , leucine-rich repeat kinase 2 (LRRK2) , LILRB2, matrix metalloproteinases (MMPs) , membrane spanning 4-domains A4A (MS4A4A) , membrane spanning 4-domains A4E (MS4A4E) , membrane spanning 4-domains A 6A (MS4A6A) , p-glucocerebrosidase (GCase or GBA) , p75 neurotrophin receptor (p75NTR) , parkin, paired immunoglobin like type 2 receptor alpha (PILRA) , phosphorylated Tau, prion protein (PrP) , presenilin 1, presenilin 2, progranulin (PGRN) , prosaposin (PSAP) , sialic acid binding Ig-like lectin 11 (Siglec11) , sialic acid binding Ig-like lectin 5 (Siglec5) , sialic acid binding Ig-like lectin 7 (Siglec7) , sialic acid binding Ig-like lectin 9 (Siglec9) , sortilin (SORT) , sphingolipids, Tau protein, transmembrane protein 106B (TMEM106b) , triggering receptor expressed on myeloid cells 2 (TREM2) , TXNRD1, and ubiquitin protein ligase E3A (UBE3A) .

The fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein can comprise a constant region. In some embodiments, a constant region is a human constant region. The constant region can be a light chain constant region. The constant region can be a human light chain constant region. The constant region can be a heavy chain constant region. The constant region can be a human heavy chain constant region. The constant region can be an IgG constant region. The constant region can be an IgG1 constant region. The constant region can be an IgG2 constant region. The constant region can be an IgG4 constant region. The constant region can be a human IgG constant region. The constant region can be a human IgG1 constant region. The constant region can be a human IgG2 constant region. The constant region can be a human IgG4 constant region.

In some embodiments, the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein comprise a heavy chain and a light chain. With respect to the heavy chain, in some embodiments, the heavy chain of an antigen-binding protein described herein can be an alpha (α) , delta (δ) , epsilon (ε) , gamma (γ) , and mu (μ) . heavy chain. In some embodiments, the heavy chain can comprise a human alpha (α) , delta (δ) , epsilon (ε) , gamma (γ) , and mu (μ) heavy chain. In some embodiments, the heavy chain comprises a human gamma (γ) heavy chain constant region. In some embodiments, the heavy chain of comprises the amino acid sequence of an IgG1 heavy chain constant region. In some embodiments, the heavy chain comprises the amino acid sequence of an IgG2 (e.g., IgG2a or IgG2b) heavy chain constant region. In some embodiments, the heavy chain comprises the amino acid sequence of an IgG4 heavy chain constant region. With respect to the light chain, in some embodiments, the light chain is a kappa light chain. In some embodiments, the light chain is a lambda light chain. In some embodiments, the light chain is a human kappa light chain or a human lambda light chain.

In some embodiments, the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein comprise constant regions comprising the amino acid sequences of the constant regions of an IgG, IgE, IgM, IgD, IgA, or IgY immunoglobulin molecule, or a human IgG, IgE, IgM, IgD, IgA, or IgY immunoglobulin molecule. In some embodiments, the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein comprise constant regions comprising the amino acid sequences of the constant regions of an IgG, IgE, IgM, IgD, IgA, or IgY immunoglobulin molecule, any class (e.g., IgG1, IgG2, IgG3, IgG4, IgAl, and IgA2) , or any subclass (e.g., IgG2a and IgG2b) of immunoglobulin molecule. In some embodiments, the constant regions comprise the amino acid sequences of the constant regions of a human IgG, IgE, IgM, IgD, IgA, or IgY immunoglobulin molecule, any class (e.g., IgG1, IgG2, IgG3, IgG4, IgAl, and IgA2) , or any subclass (e.g., IgG2a and IgG2b) of immunoglobulin molecule. Non-limiting examples of human constant region sequences have been described in e.g., U.S. Patent No. 5,693,780 and Kabat EA et al., (1991) SEQUENCES OF PROTEINS OF IMMUNOLOGICAL INTEREST, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242) .

It is known in the art that the constant regions of an antibody mediate several effector functions and these effector functions can vary depending on the isotype of the antibody. For example, binding of the C1 component of complement to the Fc region of IgG or IgM antibodies (bound to antigen) activates the complement system. Activation of complement is important in the opsonization and lysis of cell pathogens. The activation of complement also stimulates the inflammatory response and can be involved in autoimmune hypersensitivity. In addition, the Fc region of an antibody can bind a cell expressing a Fc receptor (FcR) . There are a number of Fc receptors which are specific for different classes of antibody, including IgG (gamma receptors) , IgE (epsilon receptors) , IgA (alpha receptors) and IgM (mu receptors) . Binding of antibody to Fc receptors on cell surfaces triggers a number of important and diverse biological responses including engulfment and destruction of antibody-coated particles, clearance of immune complexes, lysis of antibody-coated target cells by killer cells (called antibody-dependent cell cytotoxicity or ADCC) , release of inflammatory mediators, placental transfer, and control of immunoglobulin production.

In some embodiments, at least one or more of the constant regions has been modified or deleted in the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein. In some embodiments, the antibodies comprise modifications to one or more of the three heavy chain constant regions (CH1, CH2 or CH3) and/or to the light chain constant region (CL) .

In some embodiments, the heavy chain constant region of the modified antibodies comprises at least one human constant region. In some embodiments, the heavy chain constant region of the modified antibodies comprises more than one human constant region. In some embodiments, modifications to the constant region comprise additions, deletions, or substitutions of one or more amino acids in one or more regions. In some embodiments, one or more regions are partially or entirely deleted from the constant regions of the modified antibodies. In some embodiments, the entire CH2 domain has been removed from an antibody (ΔCH2 constructs) . In some embodiments, a deleted constant region is replaced by a short amino acid spacer that provides some of the molecular flexibility typically imparted by the absent constant region. In some embodiments, a modified antibody comprises a CH3 domain directly fused to the hinge region of the antibody. In some embodiments, a modified antibody comprises a peptide spacer inserted between the hinge region and modified CH2 and/or CH3 domains.

In some embodiments, the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein can comprise an Fc domain or fragment thereof. In some embodiments, an Fc domain is of IgG class, the IgM class, or the IgA class. In some embodiments, an Fc domain or fragment thereof is an IgG Fc domain or fragment thereof. In some embodiments, an Fc domain or fragment thereof is a human IgG Fc domain or fragment thereof. In some embodiments, an Fc domain or fragment thereof is a human IgG1 Fc domain or fragment thereof. In some embodiments, an Fc domain or fragment thereof is a human IgG2 Fc domain or fragment thereof. In some embodiments, an Fc domain or fragment thereof is a human IgG4 Fc domain or fragment thereof.

In some embodiments, the modified antibodies (e.g., modified Fc region) provide altered effector functions that, in turn, affect the biological profile of the antibody. For example, in some embodiments, the deletion or inactivation (through point mutations or other means) of a constant region reduces Fc receptor binding of the modified antibody as it circulates. In some embodiments, the constant region modifications reduce the immunogenicity of the antibody. In some embodiments, the constant region modifications increase the serum half-life of the antibody. In some embodiments, the constant region modifications reduce the serum half-life of the antibody. In some embodiments, the constant region modifications decrease or remove ADCC and/or CDC of the antibody. In some embodiments, specific amino acid substitutions in a human IgG1 Fc region with corresponding IgG2 or IgG4 residues reduce effector functions (e.g., ADCC and CDC) in the modified antibody. In some embodiments, an antibody does not have one or more effector functions (e.g., “effectorless” antibodies) . In some embodiments, the antibody does not bind an Fc receptor and/or complement factors. In some embodiments, the antibody has no effector function (s) . In some embodiments, the constant region is modified to eliminate disulfide linkages or oligosaccharide moieties. In some embodiments, the constant region is modified to add/substitute one or more amino acids to provide one or more oligosaccharide, or carbohydrate attachment sites. In some embodiments, the fusion proteins or multispecific antibodies (e.g., bispecific antibodies) provided herein can comprise a modified Fc domain as compared to a native Fc region.

In some embodiments of the fusion proteins or antibodies provided herein, the Fc domain comprises one or more amino acid substitution that reduces binding to an Fc receptor. The Fc receptor can be a human Fc receptor. The Fc receptor can be an Fcγ receptor. The Fc receptor can be an activating Fc receptor. The Fc receptor can be an activating human Fcγ receptor, such as a human Fcγ RIIIa, Fcγ RI or Fcγ RIIa. In some embodiments of the antibodies provided herein, the Fc domain comprises one or more amino acid substitution that reduces the effector function. In some embodiments of the antibodies provided herein, the same one or more amino acid substitution is present in each of the two subunits of the Fc region. In one aspect, the one or more amino acid substitution reduces the binding affinity of the Fc region to an Fc receptor. In one aspect, the one or more amino acid substitution reduces the binding affinity of the Fc region to an Fc receptor by at least 2-fold, at least 5-fold, or at least 10-fold.

Variants with reduced effector functions are known in the art and can be incorporated in the antibodies disclosed herein. For example, amino acid substitutions are known to reduce effector function. hIgG1 L235A/G237A/E318A antibody is unable to bind to human cell lines expressing FcγRs, resulting in reduced ADCC. hIgG1 and hIgG4 antibodies with L234A/L235A Fc domains have no detectable binding to the low affinity FcγRs and C1q and significantly reduced ADCC and CDC. The D266S mutation also reduces binding to FcγRs and C1q, similar to L234A and L235A. Mutations at specific residues in hIgG1 known to interact with both FcγRs and C1q, such as amino acid substitutions L234F/L235E/P331S, can reduce binding to the low affinity FcγRs and result in no detectable binding to FcγRI. The G236R/L328R mutation pair reduces or completely abrogates binding to the FcγRs. S267E substitution also reduces binding for all low affinity hFcγRs. S267K substitution combined with a series of mutations in the lower hinge of hIgG2 (E233P/L234V/L235A mutations and a deletion of residue G236) and incorporated into a hIgG1 background result in a lack of binding to all hFcγR. P329G disrupts the interaction between hIgG and hFcγR. The triple mutant L234A/L235A/P329G has no detectable binding to C1q or FcγRs, resulting in abrogated ADCC when introduced into a hIgG1. Combined point mutations of N297Q, L234F, L235E, D265A, P331S ablate Fc function. The combination of L234F/L235E/D265A potently silences the Fc region, resulting in no detectable binding to FcyRI, reduced binding to the low affinity FcyRs and reduced binding to C1q. From the site saturation mutagenesis libraries centered about the Fc C′/E loop, the S298G/T299A mutations are found to abolish or significantly reduce binding to C1q and most FcγRs except for FcγRIIA-R131 and FcγRIIB.

Additionally, glycoengineering techniques can be used to generate antibodies with reduced effector functions. The N297 glycan is central to the binding between hIgG1 and FcγRs and C1q. As such, amino acid mutations at this site which remove this glycan, including N297A, N297Q and N297G, can reduce binding to all FcγRs and C1q, resulting in reduction of ADCC and CDC.

For hIgG4, which has low affinity for all FcγR, the serine at position 228 plays a pivotal role in F (ab) arm exchange. The S228P substitution can provide homogeneous hIgG4, and is commonly introduced in therapeutic hIgG4 antibodies. Based upon its inherent lack of effector function, the human γ4 constant region can be used in Fc-silencing approaches. For example, exchanging the human γ1 region with that of human γ4 can reduce effector functionality. Murine IgG2b isotype, which also has low FcγR binding activity, differs from hIgG4 at position 235. Incorporating the mouse IgG2b residue (glutamic acid) into the hIgG4 antibody at this position can further minimize Fc effector function, resulting in an antibody (with the S228P/L235E mutations) with substantially reduced, if any, binding to all FcγRs and C1q, and no measurable ADCC. Additionally, rather than replacing the whole constant region of hIgG1 with hIgG4, specific amino acids from human γ4 can be introduced into antibodies of other IgG isotypes. For example, a combination of amino acid mutations-H268Q/V309L/A330S/P331S (IgG2m4) , when introduced into a hIgG2 backbone, can lead to no detectable binding to hFcγRI, hFcγRIIIA or C1q, reduced binding to hFcγRIIB and no change in binding to FcγRIIA-H131 when compared to the WT hIgG2 antibody. For another example, the V234A/G237A/P238S/H268A/V309L/A330S/P331S (IgG2c4d) mutations, where multiple residues within the hIgG2 constant region are replaced with IgG4 residues, can result in no detectable binding to any FcγRs or C1q and no measurable ADCC, ADCP or CDC when compared to the WT hIgG2 counterpart.

Accordingly, for illustrative purposes, such variants include: aglycosylation (N297A/Q/G; or “NA” ) , L235A/G237A/E318A ( “AAA” ) , L234A/L235A ( “LALA” ) , L234A/L235A/D266S ( “AAS” ) , S228P/L235E ( “IgG4 PE” ) , G236R/L328R ( “RR” ) , S298G/T299A ( “GA” ) , L234F/L235E/P331S ( “FES” ) , H268Q/V309L/A330S/P331S ( “IgG2m4” ) , E233P/L234V/L235A/deletion of G236/S267K, L234A/L235A/P329G ( “LALAPG” ) , V234A/G237A/P238S/H268A/V309L/A330S/P331S ( “IgG2c4d” ) , and L234F/L235E/D265A ( “FEA” ) . (See Liu et al., Antibodies 9.4 (2020) : 64; Delidakis et al., Annual review of biomedical engineering 24 (2022) : 249-274, both incorporated herein by reference in their entireties) . As a person of ordinary skill in the art would understand, the fusion proteins and antibodies disclosed herein are not limited by specific Fc modifications, and any combination and permutations of the Fc modifications disclosed herein or otherwise known in the art that reduce the effector function or binding affinity to FcγR can be adopted.

In some embodiments, Fc mutations are incorporated to improve serum half-life. Exemplary mutations include, for example, M252Y/S254T/T256E (YTE) substitutions, M428L/N434S (LS) substitutions, T307A/E380A/N434A (TM) substitutions, and H433K/N434F (HS) substations. These mutations are specifically designed to enhance the interaction of the antibody with the FcRn receptor, thereby reducing lysosomal degradation and prolonging the antibody's circulation time in the bloodstream.

In some embodiments, fusion proteins or multispecific antibodies (e.g., bispecific antibodies) disclosed herein comprise an anti-CD98 antigen-binding fragment disclosed herein, a second antibody or antigen-binding fragment that targets a CNS antigen or a brain antigen, and a modified Fc domain. In some embodiments, the modified Fc domain has reduced effector function. In some embodiments, the modified domain has improved half-life. In some embodiments, the modified Fc domain has L234A/L235A/D266S ( “AAS” ) substitutions. In some embodiments, the modified Fc domain has M252Y/S254T/T256E (YTE) substitutions. In some embodiments, the modified Fc domain has L234A/L235A/D266S ( “AAS” ) substitutions and M252Y/S254T/T256E (YTE) substitutions.

In some embodiments, provided herein are bispecific antibodies comprising an anti-CD98hc antibody or antigen-binding fragment described herein and a second antibody or antigen-binding fragment that specifically binds to a CNS antigen. Various formats of bispecific antibodies have been developed and are known in the art. As a person of ordinary skill would understand, the bispecific antibodies of present disclosure are not limited by any specific format (e.g., Brinkmann and Kontermann. MAbs. 9: 2 (2017) ; Kontermann and Brinkmann, Drug Discov Today, (2015) 20 (7) : 838-47) . Accordingly, bispecific proteins of the present disclosure can include various configurations having a first antigen-binding domain that binds to human CD98hc and a second antigen-binding domain, e.g., that binds to a CNS antigen or a brain antigen.

Examples of bispecific molecules that can be used in the present disclosure include, IgG-like bispecific antibodies and non-IgG-like bispecific antibodies. In some embodiments, the bispecific antibodies provided herein can be IgG-like bispecific antibodies. These antibodies have been engineered to promote heterologous Fc matching and include several platforms, including (1) Knobs-into-Holes, which involves modifying the CH3 region of one antibody chain to form a “knob” and the other to form a “hole, ” promoting efficient heterodimerization; (2) SEED, which alternates sequences from IgA and IgG to create complementary domains, enhancing heterodimer formation; (3) DEKK, which uses mutations to form salt bridges, stabilizing the interaction between the heavy chains; (4) ART-Ig, which promotes recombination by introducing different charges in the Fc region; (5) Orthogonal Fab, which introduces mutations to generate an orthogonal interface, allowing correct assembly of different Fab domains; (6) DuoBody, which utilizes controlled Fab-arm exchange (cFAE) technology; (7) DVD-Ig and FIT-Ig, which feature symmetrical structures with four antigen-binding sites, allowing simultaneous targeting of two different antigens; (8) two-in-one platform or dual action fab (DAF) , which uses phage display technology to optimize the original antibody with changes to residues in VL CDRs to specifically bind to the second target while retaining the ability to bind to the first target; (9) CrossMab and Wuxibody, which are both used for resolving the BsAb light chain mismatch. In some embodiments, the bispecific antibodies provided herein can be non-IgG-like bispecific antibodies. These formats lack the Fc segment, making them easier to produce with lower immunogenicity, including (1) Bispecific T-cell engagers (BiTEs) , which use linkers to connect two scFvs, redirecting T cells to cancer cells; (2) Dual-affinity retargeting molecules (DARTs) , which involve linking VH and VL sequences with interchain disulfide bonds; (3) TandAbs, which are tetravalent antibodies having two binding sites for each of the two antigens; (4) Bi-Nanobody, which onnects the VH regions of two or more antibodies, creating stable and permeable molecules. Ma et al. (2021) . Front Immunol. 12: 626616.

In some embodiments, bispecific antibodies provided herein can be in IgG-scFv format. Specifically, bispecific antibodies provided herein can comprise an IgG that specifically binds to a CNS antigen or a brain antigen, and an anti-CD98 antibody scFv disclosed herein. The anti-CD98hc scFv can comprise any VH/VL pair disclosed herein. In some embodiments, one anti-CD98hc scFv is linked to the C-terminus of one of the two heavy chains of the IgG (2+1 format) . In some embodiments, two anti-CD98hc scFvs are linked to the C-terminus of both heavy chains of the IgG (2+2 format) . The two CD98hc scFvs can have the same sequence or different sequences. In some embodiments, the anti-CD98 scFv is linked to the IgG via a peptide linker. The linker can be, for example, 1 to 20 amino acids in length. The linker can comprise the amino acid sequence (GGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 128) . The linker can comprise the amino acid sequence (GGGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 129) . The linker can comprise the amino acid sequence (GGGGS) 3 (SEQ ID NO: 130) . The linker can comprise the amino acid sequence GTEGKSSGSGSESKST (SEQ ID NO: 131) . The linker can comprise the amino acid sequence GGAGGA (SEQ ID NO: 132) . A person of ordinary skill in the art would understand that the bispecific antibodies disclosed herein are not limited by the specific linkers exemplified herein. Any peptide linker with the appropriate length and flexibility that allows both the IgG and the scFv to properly bind their targets can be used.
6.4 Bispecific antibodies targeting LILRB2

Leukocyte Immunoglobulin-Like Receptor Subfamily B Member 2 (LILRB2) , also known as CD85j or ILT4, is a transmembrane protein that plays a significant role in the regulation of immune responses. This receptor is part of the larger immunoglobulin superfamily and is predominantly expressed on myeloid cells, including monocytes, macrophages, dendritic cells, and certain subsets of lymphocytes. LILRB2 consists of an extracellular domain with multiple immunoglobulin-like domains, a transmembrane region, and a cytoplasmic tail containing immunoreceptor tyrosine-based inhibitory motifs (ITIMs) . These ITIMs are crucial for the receptor's inhibitory signaling function, as they recruit phosphatases like SHP-1 and SHP-2 upon activation, leading to downstream signaling events that dampen immune responses.

LILRB2 functions primarily as an inhibitory receptor. Its main role is to modulate the immune response by delivering negative signals that inhibit the activation and proliferation of immune cells. This regulatory mechanism is essential for maintaining immune homeostasis and preventing excessive inflammation or autoimmunity. LILRB2 interacts with various ligands, including major histocompatibility complex (MHC) class I molecules and beta-amyloid plaques, to exert its effects. The interaction between LILRB2 and beta-amyloid influences microglial activity, leading to altered immune responses in the brain. By modulating the activation and phagocytic activity of microglia, LILRB2 affects the clearance of beta-amyloid and the overall inflammatory environment in the brain. By regulating microglial activity, LILRB2 plays a role in various neurological conditions where inflammation is a key component.

An exemplary sequence of human LILRB2 is provided below (Uniprot Accession No. Q8N423-2, SEQ ID NO: 133) . More information about human LILRB2 can be found on public databases with the following IDs: HGNC: 6711; NCBI Gene: 10288; Ensembl: ENSG00000151067; 604821; UniProtKB/Swiss-Prot: Q8N423.

In some embodiments, provided herein are bispecific antibodies that specifically bind to LILRB2 and CD98hc. In some embodiments, the bispecific antibodies are chimeric antibodies. In some embodiments, the bispecific antibodies are humanized antibodies. In some embodiments, the bispecific antibodies are human antibodies. In some embodiments, the bispecific antibodies are monoclonal antibodies.

In some embodiments, the bispecific antibodies comprise a VH1/VL1 pair that specifically targets LILRB2. In some embodiments, the bispecific antibodies comprise a VH2/VL2 pair that specifically targets CD98hc. The VH2/VL2 pair that specifically targets CD98hc can be any VH/VL pair described in present disclosure. In some embodiments, the VH2/VL2 pair can have the amino acid sequences of (1) SEQ ID NOs: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively; or humanized versions thereof. In some embodiments, the VH2/VL2 pair can have the amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.

In some embodiments, the bispecific antibodies comprise a VH1/VL1 pair that specifically targets LILRB2, wherein the VH1 has VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 122, 123 and 124, respectively, and the VL1 having VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 125, 126, and 127 respectively; or a variant thereof having up to about 3, about 5, about 8, about 10, about 12, or about 15 amino acid substitutions, additions, and/or deletions in the VH CDRs and/or VL CDRs. In some embodiments, provided herein are antibodies or antigen-binding fragments thereof that specifically bind LILRB2 comprising: (a) a VH1 having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 120; and (b) a VL1 having at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 121. In some embodiments, the VH1 and VL1 have the amino acid sequences of SEQ ID NOs: 120 and 121, respectively.

The anti-LILRB2/CD98hc bispecific antibodies disclosed herein can be in any format known in the art. In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies provided herein can be IgG-like bispecific antibodies. These antibodies have been engineered to promote heterologous Fc matching and include several platforms, including (1) Knobs-into-Holes, which involves modifying the CH3 region of one antibody chain to form a “knob” and the other to form a “hole, ” promoting efficient heterodimerization; (2) SEED, which alternates sequences from IgA and IgG to create complementary domains, enhancing heterodimer formation; (3) DEKK, which uses mutations to form salt bridges, stabilizing the interaction between the heavy chains; (4) ART-Ig, which promotes recombination by introducing different charges in the Fc region; (5) Orthogonal Fab, which introduces mutations to generate an orthogonal interface, allowing correct assembly of different Fab domains; (6) DuoBody, which utilizes controlled Fab-arm exchange (cFAE) technology; (7) DVD-Ig and FIT-Ig, which feature symmetrical structures with four antigen-binding sites, allowing simultaneous targeting of two different antigens; (8) two-in-one platform or dual action fab (DAF) , which uses phage display technology to optimize the original antibody with changes to residues in VL CDRs to specifically bind to the second target while retaining the ability to bind to the first target; (9) CrossMab and Wuxibody, which are both used for resolving the BsAb light chain mismatch. In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies provided herein can be non-IgG-like bispecific antibodies. These formats lack the Fc segment, making them easier to produce with lower immunogenicity, including (1) Bispecific T-cell engagers (BiTEs) , which use linkers to connect two scFvs, redirecting T cells to cancer cells; (2) Dual-affinity retargeting molecules (DARTs) , which involve linking VH and VL sequences with interchain disulfide bonds; (3) TandAbs, which are tetravalent antibodies having two binding sites for each of the two antigens; (4) Bi-Nanobody, which onnects the VH regions of two or more antibodies, creating stable and permeable molecules. Ma et al. (2021) . Front Immunol. 12: 626616.

Table 11: Sequences for exemplary anti-LILRB2 antibody

In some embodiments, bispecific antibodies provided herein can be in IgG-scFv format. Specifically, bispecific antibodies provided herein can comprise an IgG that specifically binds to a LILRB2, and an anti-CD98 antibody scFv disclosed herein. The anti-CD98hc scFv can comprise any VH/VL pair disclosed herein. In some embodiments, one anti-CD98hc scFv is linked to the C-terminus of one of the two heavy chains of the anti-LILRB2 IgG (2+1 format) . In some embodiments, two anti-CD98hc scFvs are linked to the C-terminus of both heavy chains of the anti-LILRB2 IgG (2+2 format) . The two CD98hc scFvs can have the same sequence or different sequences. In some embodiments, the anti-CD98 scFv is linked to the IgG via a peptide linker. The linker can be, for example, 1 to 20 amino acids in length. The linker can comprise the amino acid sequence (GGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 128) . The linker can comprise the amino acid sequence (GGGGS) n, n=1, 2, 3, 4, or 5 (SEQ ID NO: 129) . The linker can comprise the amino acid sequence (GGGGS) 3 (SEQ ID NO: 130) . The linker can comprise the amino acid sequence GTEGKSSGSGSESKST (SEQ ID NO: 131) . The linker can comprise the amino acid sequence GGAGGA (SEQ ID NO: 132) . A person of ordinary skill in the art would understand that the bispecific antibodies disclosed herein are not limited by the specific linkers exemplified herein. Any peptide linker with the appropriate length and flexibility that allows both the IgG and the scFv to properly bind their targets can be used.

Provided herein are bispecific antibody for CD98hc and LILBR2, comprising (1) a first peptide chain (HC1) comprising, from N-terminus to C-terminus, VH1 and a first CH region, and a scFv; (2) a second peptide chain (HC2) comprising, from N-terminus to C-terminus, VH1 and a second CH region; and (3) a third peptide chain (LC) comprising, from N-terminus to C-terminus, VL1 and a CL region. In some embodiments, the VH1 and VL1 have the amino acid sequences of SEQ ID NOs: 120 and 121, respectively. In some embodiments, the scFv comprises VH2 and VL2, wherein the VH2/VL2 pair can be any VH/VL pair that specifically targets CD98 disclosed herein. In some embodiments, the scFv comprises VH2 and VL2 having the amino acid sequences of (1) SEQ ID NOs: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively; or humanized versions thereof. In some embodiments, the VH2 and VL2 have amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.

In some embodiments of the anti-LILRB2/CD98hc bispecific antibodies disclosed herein, the anti-CD98hc scFv has at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-101 and 138. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 92. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 93. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 94. In some embodiments, the anti-CD98hc scFv has the amino acid sequence of SEQ ID NO: 95.

The amino acid sequences of the CL region and the CH region of the bispecific antibodies disclosed herein can be derived from any appropriate source, e.g., a constant region of an antibody such as an IgG1, IgG2, IgG3, or IgG4. In some embodiments, the constant regions of the bispecific antibodies provided herein are derived from human IgG. In some embodiments, the constant regions of the bispecific antibodies provided herein are derived from human IgG1. In some embodiments, the constant regions of the bispecific antibodies provided herein are derived from human IgG2. In some embodiments, the constant regions of the bispecific antibodies provided herein are derived from human IgG3. In some embodiments, the constant regions of the bispecific antibodies provided herein are derived from human IgG4. In some embodiments, the amino acid sequences of the CL region and the CH of the bispecific antibodies disclosed herein can comprise one or more amino acid substitutions, additions, or deletions that differ from the wildtype immunoglobulin, e.g., one or more amino acid substitutions in a wild type IgG1 or IgG4. Such mutations are known in the art (see, e.g., US7704497, US7083784, US6821505, US 8323962, US6737056, and US7416727) .

The bispecific antibodies provided herein comprise a first CH region, a second CH region, and a CL region. In some embodiments, the CL region is Cκ (SEQ ID NO: 134) or Cλ (SEQ ID NO: 135) , or a variant thereof having up to ten amino acids substitutions, additions, and/or deletions. In some embodiments, the VL region is Cκ (SEQ ID NO: 134) . In some embodiments, the VL region is Cλ (SEQ ID NO: 135) .

The bispecific antibodies provided herein comprise a first CH region and a second region, which can be human IgG1 CH region, human IgG2 CH region, human IgG3 CH region, or human IgG4 CH region, or a variant thereof having up to ten amino acids substitutions, additions, and/or deletions. In some embodiments, bispecific antibodies provided herein comprise

In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions having up to three, up to five, up to eight, up to ten, and up to twenty amino acid substitutions, additions, and/or deletions.

In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions with mutations to reduce the effector function. In some embodiments, the modification can be aglycosylation (N297A/Q/G; or “NA” ) , L235A/G237A/E318A ( “AAA” ) , L234A/L235A ( “LALA” ) , L234A/L235A/D266S ( “AAS” ) , S228P/L235E ( “IgG4 PE” ) , G236R/L328R ( “RR” ) , S298G/T299A ( “GA” ) , L234F/L235E/P331S ( “FES” ) , H268Q/V309L/A330S/P331S ( “IgG2m4” ) , E233P/L234V/L235A/deletion of G236/S267K, L234A/L235A/P329G ( “LALAPG” ) , V234A/G237A/P238S/H268A/V309L/A330S/P331S ( “IgG2c4d” ) , and L234F/L235E/D265A ( “FEA” ) . In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions with L234A/L235A/D266S ( “AAS” ) substitutions.

In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions with mutations to improve serum half-life. Exemplary mutations include, for example, M252Y/S254T/T256E (YTE) substitutions, M428L/N434S (LS) substitutions, T307A/E380A/N434A (TM) substitutions, and H433K/N434F (HS) substations.

In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions with reduced effector function and improved half-life. In some embodiments, the first and second CH regions of the bispecific antibodies provided herein are human IgG1 CH regions with M252Y/S254T/T256E (YTE) substitutions.

In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies provided herein comprises a mutation to promote heterodimerization of Fc regions. In some embodiments, a dimerized Fc region of a bispecific provided herein is formed by Fc regions that contain amino acid mutations, substitutions, additions, or deletions to promote heterodimerization in which different polypeptides comprising different Fc regions can dimerize to yield a heterodimer configuration. In some embodiments, a bispecific of the present disclosure comprises a first Fc sequence comprising a first CH3 region, and a second Fc sequence comprising a second CH3 region, wherein the sequences of the first and second CH3 regions are different and are such that the heterodimeric interaction between said first and second CH3 regions is stronger than each of the homodimeric interactions of said first and second CH3 regions

Methods to promote heterodimerization of Fc regions include amino acid deletions, additions, or substitutions of the amino acid sequence of the Fc region, such as by including a set of “knob-into-hole” deletions, additions, or substitutions or including amino acid deletions, additions, or substitutions to effect electrostatic steering of the Fc to favor attractive interactions among different polypeptide chains. Methods for promoting heterodimerization of complementary Fc polypeptides have been previously described in, for example, Ridgway et al., 1996, Protein Eng, 9: 617-621; Merchant et al., 1998, Nature Biotechnol, 16: 677-681; Moore et al., 2011, MAbs, 3: 546-557; Von Kreudenstein et al., 2013, 5: 646-654; Gunasekaran et al., 2010, J Biol Chem, 285: 19637-19464; Leaver-Fay et al., 2016, Structure, 24: 641-651; Ha et al., 2016, Frontiers in Immunology, 7: 1; Davis et al., 2010, Protein Eng Des Sei, 23: 195-202; W01996/027011; WO 1998/050431; W02006/028936; W02009/089004; WO2011/143545; WO2014/067011; WO2012/058768; WO2018/027025; US2014/0363426; US2015/0307628; US2018/0016354; US2015/0239991; US2017/0058054; USPN5731168; USPN7183076; USPN9701759; USPN9605084; USPN9650446; USPN8216805; USPN8765412; and USPN8258268.

In some embodiments, bispecific antibodies provided herein have complementary Fc polypeptides to form heterodimer of the “knob-into-hole” configurations or “KIH” configuration. “Knob-into-hole” technology is described in e.g., U.S. Pat. Nos. 5,731,168; 7,695,936; 8,216,805; 8,765,412; Ridgway et al., Prot Eng 9, 617-621 (1996) ; and Carter, J Immunol Meth 248, 7-15 (2001) . Generally, the method involves introducing a protuberance ( “knob” ) at the interface of a first polypeptide and a corresponding cavity ( “hole” ) in the interface of a second polypeptide, such that the protuberance can be positioned in the cavity so as to promote heterodimer formation and hinder homodimer formation. Protuberances are constructed by replacing small amino acid side chains from the interface of the first polypeptide with larger side chains (e.g., tyrosine or tryptophan) . Compensatory cavities of identical or similar size to the protuberances are created in the interface of the second polypeptide by replacing large amino acid side chains with smaller ones (e.g., alanine or threonine) . The protuberance and cavity can be made by altering the nucleic acid encoding the polypeptides, e.g., by site-specific mutagenesis, or by peptide synthesis. In some embodiments, a knob modification comprises the amino acid substitution T366W in one of the two subunits of the Fc domain, and the hole modification comprises the amino acid substitutions T366S, L368A and Y407V in the other one of the two subunits of the Fc domain. In some embodiments, the subunit of the Fc domain comprising the knob modification additionally comprises the amino acid substitution S354C, and the subunit of the Fc domain comprising the hole modification additionally comprises the amino acid substitution Y349C. Introduction of these two cysteine residues results in the formation of a disulfide bridge between the two subunits of the Fc domain, thus further stabilizing the dimer (Carter, J Immunol Methods 248, 7-15 (2001) ) . Thus, in such configurations, a first Fc polypeptide comprises amino acid modifications to form the “knob” and a second Fc polypeptide comprises amino acid modifications to form the “hole” thus forming an Fc heterodimer comprising complementary Fc polypeptides.

In some embodiments, complementary Fc polypeptides of an Fc heterodimer include a mutation to alter charge polarity across the Fc dimer interface such that co-expression of electrostatically matched Fc regions support favorable attractive interactions, thereby promoting desired Fc heterodimer formation; whereas unfavorable repulsive charge interactions suppress unwanted Fc homodimer formation (Guneskaran et al., 2010, J Biol Chem, 285: 19637-19646) . When co-expressed in a cell, association between the polypeptide chains is possible but the chains do not substantially self-associate due to charge repulsion.

Exemplary paired amino acid modifications of complementary Fc polypeptides of an Fc heterodimeric configuration are set forth below in the table below (EU numbering) .

Table 12: Exemplary paired Fc modifications for heterodimeric Fc domains

The anti-LILRB2/CD98hc bispecific antibodies disclosed herein can comprise complementary Fc regions having the modifications described in Table 12 above. In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies disclosed herein comprises a first CH region and a second CH region comprising paired Fc modification described in Table 12 above. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have T366Y substitution and Y407T, respectively, or vice versa.

In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have T366W substitution and T366S/L368W/Y407V substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have T366W substitution and T366S/L368A/Y407V substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have T366W/S354C substitutions and T366S/L368A/Y407V/Y349C substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have T350V/L351Y/F405A/Y407V substitutions and T350V/T366L/K392L/T394W substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have K360D/D399M/Y407A substitutions and E345R/Q347R/T366V/K409V substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have K409D/K392D substitutions and D399K/E356K substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have K360E/K409W substitutions and Q347R/D399V/F405T substitutions, respectively, or vice versa. In some embodiments, the first CH region and the second CH region of the bispecific antibodies disclosed herein have L360E/K409W/Y349C substitutions and
Q347R/D399V/F405T/S354C substitutions, respectively, or vice versa. In some embodiments, the
first CH region and the second CH region of the bispecific antibodies disclosed herein have K370E/K409W substitutions and E357N/D399V/F405T substitutions, respectively, or vice versa.

In some embodiments, in the bispecific antibody disclosed herein, the first CH region further has T350V, L351Y, F405A, and Y407V substitutions and the second CH region has T350V, T366L, K392L, and T394W substitutions.

In some embodiments, to further reduce formation of homodimers, one of the CH regions further has H435R and Y436F substitutions. In some embodiments, the second CH region further has H435R and Y436F substitutions

Table 13: Sequences of Exemplary Bispecific Antibodies

In some embodiments, provided herein are bispecific antibody that specifically bind to human LILRB2 and human CD98hc, wherein the bispecific antibody has a first peptide chain (HC1) , a second peptide chain (HC2) , and a third peptide chain (LC) , wherein HC1 has an amino acid sequence that is at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 85 and 88-91, HC2 has an amino acid sequence that is at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%identical to SEQ ID NO: 86, and LC1 has an amino acid sequence that is at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%identical to SEQ ID NO: 87. In some embodiments, HC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 85. HC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 85. HC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 85. HC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 85. HC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 85. HC1 can have the amino acid sequence of SEQ ID NO: 85. In some embodiments, HC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 88. HC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 88. HC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 88. HC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 88. HC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 88. HC1 can have the amino acid sequence of SEQ ID NO: 88. In some embodiments, HC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 89. HC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 89. HC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 89. HC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 89. HC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 89. HC1 can have the amino acid sequence of SEQ ID NO: 89. In some embodiments, HC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 90. HC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 90. HC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 90. HC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 90. HC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 90. HC1 can have the amino acid sequence of SEQ ID NO: 90. In some embodiments, HC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 91. HC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 91. HC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 91. HC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 91. HC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 91. HC1 can have the amino acid sequence of SEQ ID NO: 91. In some embodiments, HC2 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 86. HC2 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 86. HC2 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 86. HC2 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 86. HC2 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 86. HC2 can have the amino acid sequence of SEQ ID NO: 86. In some embodiments, LC1 has an amino acid sequence that is at least 85%identical to SEQ ID NO: 87. LC1 can have an amino acid sequence that is at least 90%identical to SEQ ID NO: 87. LC1 can have an amino acid sequence that is at least 95%identical to SEQ ID NO: 87. LC1 can have an amino acid sequence that is at least 98%identical to SEQ ID NO: 87. LC1 can have an amino acid sequence that is at least 99%identical to SEQ ID NO: 87. LC1 can have the amino acid sequence of SEQ ID NO: 87. In some embodiments, provided herein are bispecific antibody that specifically bind to human LILRB2 and human CD98hc having a first peptide chain (HC1) , a second peptide chain (HC2) , and a third peptide (LC) , wherein HC1, HC2, and LC have amino acid sequences of SEQ ID NOs: 85, 86, and 87, respectively. In some embodiments, HC1, HC2, and LC have amino acid sequences of SEQ ID NOs: 88, 86, and 87, respectively. In some embodiments, HC1, HC2, and LC have amino acid sequences of SEQ ID NOs: 89, 86, and 87, respectively. In some embodiments, HC1, HC2, and LC have amino acid sequences of SEQ ID NOs: 90, 86, and 87, respectively. In some embodiments, HC1, HC2, and LC have amino acid sequences of SEQ ID NOs: 91, 86, and 87, respectively.

In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies described herein can cross the BBB.

In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies described herein are internalizing antibodies or antigen-binding fragments. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments disclosed herein can be internalized in BBB epithelial cells greater than 10-fold as compared to internalization by an isotype control.

In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies provided herein accumulate at least 2-fold more than an isotype control in the brain. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulate at least 3, at least 4, or at least 5-fold more than an isotype control in the brain. In some embodiments, the accumulation is measured in a hCD98 knock-in mouse.

In some embodiments, anti-LILRB2/CD98hc bispecific antibodies provided herein accumulate at least 2-fold more than an isotype control in the brain parenchyma. In some embodiments, the anti-CD98hc antibodies or antigen-binding fragments provided herein accumulate at least 3, at least 4, or at least 5-fold more than an isotype control in the brain parenchyma. In some embodiments, the accumulation is measured in a hCD98 knock-in mouse.

In some embodiments, anti-LILRB2/CD98hc bispecific antibodies do not affect BBB integrity or function. In some embodiments, the anti-LILRB2/CD98hc bispecific antibodies described herein do not affect leucine uptake by CD98-expressing cells.
6.5 Polynucleotides, vectors, and cells

Provided herein are polynucleotides encoding at least one peptide chain of the anti-CD98hc antibody or anti-LILRB2/CD98hc bispecific antibodies disclosed herein. In some embodiments, the polynucleotides provided herein encode one peptide. In some embodiments, the polynucleotides provided herein encode more than one peptide. In some embodiments, the polynucleotides provided herein can encode, for example, two or three peptide chains of the anti-CD98hc antibody or bispecific antibody provided herein (e.g., the bispecific antibodies in IgG-scFv format) . In some embodiments, provided herein are polynucleotides encoding the HC1, HC2, and LC of the anti-LILRB2/CD98hc bispecific antibodies disclosed herein in the IgG-scFv format. For example, provided herein are polynucleotides encoding the HC1, HC2, and LC of the bispecific antibodies exemplified in Table 13.

Cistrons can be separated by, for example, an internal ribosomal entry site (IRES) or 2A element. An IRES, as understood in the art, refers to nucleotide sequences in an expression cassette which when transcribed into mRNA, can recruit ribosomes directly, without a previous scanning of untranslated region of mRNA by the ribosomes. A 2A element, as understood in the art, encoding self-cleaving short peptides (about 20 amino acids) that provide a mechanism for subsequent separation of equimolarly produced polypeptides of interest. Illustrative 2A self-cleaving peptides include P2A, E2A, F2A, and T2A.

As used herein, the term “encode” and its grammatical equivalents refer to the inherent property of specific sequences of nucleotides in a polynucleotide or a nucleic acid, such as a gene, a cDNA, or an mRNA, to serve as templates for synthesis of other polymers and macromolecules in biological processes having either a defined sequence of nucleotides (i.e., rRNA, tRNA and mRNA) or a defined sequence of amino acids and the biological properties resulting therefrom. Thus, a gene encodes a protein if transcription and translation of mRNA corresponding to that gene produces the protein. Unless otherwise specified, a “nucleotide sequence encoding an amino acid sequence” includes all nucleotide sequences that are degenerate versions of each other and that encode the same amino acid sequence. Nucleotide sequences that encode proteins and RNA can include introns.

The term “polynucleotide that encodes a polypeptide” encompasses a polynucleotide which includes only coding sequences for the polypeptide as well as a polynucleotide which includes additional coding and/or non-coding sequences. The polynucleotides of the disclosure can be in the form of RNA or in the form of DNA. DNA can be cDNA, genomic DNA, or synthetic DNA, and can be double-stranded or single-stranded. Single stranded DNA can be the coding strand or non-coding (anti-sense) strand. The polynucleotides of the disclosure can be mRNA.

The present disclosure also provides variants of the polynucleotides described herein, wherein the variants have a nucleotide sequence at least about 80%identical, at least about 85%identical, at least about 90%identical, at least about 95%identical, at least about 96%identical, at least about 97%identical, at least about 98%identical, or at least about 99%identical to a polynucleotide sequence encoding at least one peptide chain of a bispecific antibody described herein. As used herein, the phrase “apolynucleotide having a nucleotide sequence at least about 95%identical to a polynucleotide sequence” means that the nucleotide sequence of the polynucleotide is identical to a reference sequence except that the polynucleotide sequence can include up to five point mutations per each 100 nucleotides of the reference nucleotide sequence. In other words, to obtain a polynucleotide having a nucleotide sequence at least 95%identical to a reference nucleotide sequence, up to 5%of the nucleotides in the reference sequence can be deleted or substituted with another nucleotide, or a number of nucleotides up to 5%of the total nucleotides in the reference sequence can be inserted into the reference sequence. These mutations of the reference sequence can occur at the 5’ or 3’ terminal positions of the reference nucleotide sequence or anywhere between those terminal positions, interspersed either individually among nucleotides in the reference sequence or in one or more contiguous groups within the reference sequence.

The polynucleotide variants can contain alterations in the coding regions, non-coding regions, or both. In some embodiments, a polynucleotide variant contains alterations which produce silent substitutions, additions, or deletions, but does not alter the properties or activities of the encoded polypeptide. In some embodiments, a polynucleotide variant comprises silent substitutions that results in no change to the amino acid sequence of the polypeptide (due to the degeneracy of the genetic code) . Polynucleotide variants can be produced for a variety of reasons, for example, to optimize codon expression for a particular host (e.g., change codons in the human mRNA to those preferred by a bacterial host such as E. coli) . In some embodiments, a polynucleotide variant comprises at least one silent mutation in a non-coding or a coding region of the sequence.

In some embodiments, a polynucleotide variant is produced to modulate or alter expression (or expression levels) of the encoded polypeptide. In some embodiments, a polynucleotide variant is produced to increase expression of the encoded polypeptide. In some embodiments, a polynucleotide variant is produced to decrease expression of the encoded polypeptide. In some embodiments, a polynucleotide variant has increased expression of the encoded polypeptide as compared to a parental polynucleotide sequence. In some embodiments, a polynucleotide variant has decreased expression of the encoded polypeptide as compared to a parental polynucleotide sequence.

In some embodiments, a polynucleotide comprises the coding sequence for a polypeptide (e.g., an antibody or a fusion protein) fused in the same reading frame to a polynucleotide which aids in expression and secretion of a polypeptide from a host cell (e.g., a leader sequence which functions as a secretory sequence for controlling transport of a polypeptide) . The polypeptide can have the leader sequence cleaved by the host cell to form a “mature” form of the polypeptide.

In some embodiments, a polynucleotide comprises the coding sequence for a polypeptide (e.g., an antibody) fused in the same reading frame to a marker or tag sequence. For example, in some embodiments, a marker sequence is a hexa-histidine tag (HIS-tag) that allows for efficient purification of the polypeptide fused to the marker. In some embodiments, a marker sequence is a hemagglutinin (HA) tag derived from the influenza hemagglutinin protein when a mammalian host (e.g., COS-7 cells) is used. In some embodiments, the marker sequence is a FLAG^TM tag. In some embodiments, a marker can be used in conjunction with other markers or tags.

In some embodiments, a polynucleotide is isolated. In some embodiments, a polynucleotide is substantially pure.

In some embodiments, provided herein are also vectors comprising a polynucleotide disclosed herein. The term “vector, ” and its grammatical equivalents as used herein refer to a vehicle that is used to carry genetic material (e.g., a polynucleotide sequence) , which can be introduced into a host cell, where it can be replicated and/or expressed. Vectors applicable for use include, for example, expression vectors, plasmids, phage vectors, viral vectors, episomes and artificial chromosomes, which can include selection sequences or markers operable for stable integration into a host cell’s chromosome. Additionally, the vectors can include one or more selectable marker genes and appropriate expression control sequences. Selectable marker genes that can be included, for example, provide resistance to antibiotics or toxins, complement auxotrophic deficiencies, or supply critical nutrients not in the culture media. Expression control sequences can include constitutive and inducible promoters, transcription enhancers, transcription terminators, and the like which are well known in the art. When two or more polynucleotides are to be co-expressed, both polynucleotides can be inserted, for example, into a single expression vector or in separate expression vectors. For single vector expression, the encoding polynucleotides can be operationally linked to one common expression control sequence or linked to different expression control sequences, such as one inducible promoter and one constitutive promoter. The introduction of polynucleotides into a host cell can be confirmed using methods well known in the art. It is understood by those skilled in the art that the polynucleotides are expressed in a sufficient amount to produce a desired product, and it is further understood that expression levels can be optimized to obtain sufficient expression using methods well known in the art.

In some embodiments, vectors provided herein can be expression vectors. In some embodiments, vectors provided herein comprise a polynucleotide encoding at least one peptide chain of the bispecific antibodies described herein. In some embodiments, provided herein are recombinant expression vectors, which can be used to amplify and express a polynucleotide encoding at least one peptide chain of the bispecific antibodies described herein. For example, a recombinant expression vector can be a replicable DNA construct that includes synthetic or cDNA-derived DNA fragments encoding at least one peptide chain of the bispecific antibodies described herein, operatively linked to suitable transcriptional and/or translational regulatory elements derived from mammalian, microbial, viral or insect genes. In some embodiments, a viral vector is used. DNA regions are “operatively linked” when they are functionally related to each other. For example, a promoter is operatively linked to a coding sequence if it controls the transcription of the sequence; or a ribosome binding site is operatively linked to a coding sequence if it is positioned so as to permit translation. In some embodiments, structural elements intended for use in certain expression systems include a leader sequence enabling extracellular secretion of translated protein by a host cell. In some embodiments, in situations where recombinant protein is expressed without a leader or transport sequence, a polypeptide can include an N-terminal methionine residue.

Examples of vectors are plasmid, autonomously replicating sequences, and transposable elements. Useful expression vectors for bacterial hosts include known bacterial plasmids, such as plasmids from E. coli, including pCR1, pBR322, pMB9 and their derivatives, and wider host range plasmids, such as M13 and other filamentous single-stranded DNA phages. Additional exemplary vectors include, without limitation, plasmids, phagemids, cosmids, artificial chromosomes such as yeast artificial chromosome (YAC) , bacterial artificial chromosome (BAC) , or P1-derived artificial chromosome (PAC) , bacteriophages such as lambda phage or M13 phage, and animal viruses. Examples of categories of animal viruses useful as vectors include, without limitation, retrovirus (including lentivirus) , adenovirus, adeno-associated virus, herpesvirus (e.g., herpes simplex virus) , poxvirus, baculovirus, papillomavirus, and papovavirus (e.g., SV40) . Examples of expression vectors are pClneo vectors (Promega) for expression in mammalian cells; pLenti4/V5-DEST^TM, pLenti6/V5-DEST^TM, and pLenti6.2/V5-GW/lacZ (Invitrogen) for lentivirus-mediated gene transfer and expression in mammalian cells. Useful expression vectors for eukaryotic hosts include, for example, vectors comprising expression control sequences from SV40, bovine papilloma virus, adenovirus, and cytomegalovirus. Exemplary transposon systems such as Sleeping Beauty and PiggyBac can be used, which can be stably integrated into the genome (e.g., Ivics et al., Cell, 91 (4) : 501–510 (1997) ; et al., (2007) Nucleic Acids Research. 35 (12) : e87) .

In some embodiments, the vector is an episomal vector or a vector that is maintained extrachromosomally. As used herein, the term “episomal” refers to a vector that is able to replicate without integration into host’s chromosomal DNA and without gradual loss from a dividing host cell also meaning that said vector replicates extrachromosomally or episomally. The vector is engineered to harbor the sequence coding for the origin of DNA replication or “ori” from a lymphotrophic herpes virus or a gamma herpesvirus, an adenovirus, SV40, a bovine papilloma virus, or a yeast, specifically a replication origin of a lymphotrophic herpes virus or a gamma herpesvirus corresponding to oriP of EBV. In some embodiments, the lymphotrophic herpes virus may be Epstein Barr virus (EBV) , Kaposi's sarcoma herpes virus (KSHV) , Herpes virus saimiri (HS) , or Marek's disease virus (MDV) . Epstein Barr virus (EBV) and Kaposi's sarcoma herpes virus (KSHV) are also examples of a gamma herpesvirus. Typically, the host cell comprises the viral replication transactivator protein that activates the replication.

“Expression control sequences, ” “control elements, ” or “regulatory sequences” present in an expression vector are those non-translated regions of the vector-origin of replication, selection cassettes, promoters, enhancers, translation initiation signals (Shine Dalgarno sequence or Kozak sequence) introns, a polyadenylation sequence, 5'a nd 3'untranslated regions-which interact with host cellular proteins to carry out transcription and translation. Such elements can vary in their strength and specificity. Depending on the vector system and host utilized, any number of suitable transcription and translation elements, including ubiquitous promoters and inducible promoters can be used.

Illustrative ubiquitous expression control sequences that can be used in present disclosure include, but are not limited to, a cytomegalovirus (CMV) immediate early promoter, a viral simian virus 40 (SV40) promoter (e.g., early or late) , a Moloney murine leukemia virus (MoMLV) LTR promoter, a Rous sarcoma virus (RSV) LTR, a herpes simplex virus (HSV) (thymidine kinase) promoter, H5, P7.5, and P11 promoters from vaccinia virus, an elongation factor 1-alpha (EF1a) promoter, early growth response 1 (EGR1) , ferritin H (FerH) , ferritin L (FerL) , Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) , eukaryotic translation initiation factor 4A1 (EIF4A1) , heat shock 70kDa protein 5 (HSPA5) , heat shock protein 90kDa beta, member 1 (HSP90B1) , heat shock protein 70kDa (HSP70) , β-kinesin (β-KIN) , the human ROSA 26 locus (Irions et al., Nature Biotechnology 25, 1477 -1482 (2007) ) , a Ubiquitin C promoter (UBC) , a phosphoglycerate kinase-1 (PGK) promoter, a cytomegalovirus enhancer/chicken β-actin (CAG) promoter, and a β-actin promoter.

Illustrative examples of inducible promoters/systems include, but are not limited to, steroid-inducible promoters such as promoters for genes encoding glucocorticoid or estrogen receptors (inducible by treatment with the corresponding hormone) , metallothionine promoter (inducible by treatment with various heavy metals) , MX-1 promoter (inducible by interferon) , the “GeneSwitch” mifepristone-regulatable system (Sirin et al., 2003, Gene, 323: 67) , the cumate inducible gene switch (WO 2002/088346) , tetracycline-dependent regulatory systems, etc. The bispecific antibodies described herein can be produced by any method known in the art, including chemical synthesis and recombinant expression techniques. The practice of the invention employs, unless otherwise indicated, conventional techniques in molecular biology, microbiology, genetic analysis, recombinant DNA, organic chemistry, biochemistry, PCR, oligonucleotide synthesis and modification, nucleic acid hybridization, and related fields within the skill of the art.

The present disclosure also provides cells comprising the polynucleotides disclosed herein that encode at least one peptide chain of the bispecific antibodies described herein. In some embodiments, cells provided herein comprise a polynucleotide that encodes the anti-CD98hc antibodies disclosed herein. In some embodiments, cells provided herein comprise a polynucleotide that encodes the HC1, HC2 and LC of the anti-LILRB2/CD98hc bispecific antibodies disclosed herein in the IgG-scFv format.

Cells comprising vectors disclosed herein are also contemplated. In some embodiments, provided herein are host cells comprising a vector comprising a polynucleotide disclosed herein. In some embodiments, host cells provided herein comprise a vector or multiple vectors that collectively comprise the polynucleotides encoding the polypeptide chains of the bispecific antibodies described herein. In some embodiments, host cells provided herein produce the bispecific antibodies described herein.

Examples of suitable mammalian host cell lines include, but are not limited to, COS-7 (monkey kidney-derived) , L-929 (murine fibroblast-derived) , C127 (murine mammary tumor-derived) , 3T3 (murine fibroblast-derived) , CHO (Chinese hamster ovary-derived) , HeLa (human cervical cancer-derived) , BHK (hamster kidney fibroblast-derived) , HEK-293 (human embryonic kidney-derived) cell lines and variants thereof. Mammalian expression vectors can comprise non-transcribed elements such as an origin of replication, a suitable promoter and enhancer linked to the gene to be expressed, and other 5’ or 3’ flanking non-transcribed sequences, and 5’ or 3’ non-translated sequences, such as necessary ribosome binding sites, a polyadenylation site, splice donor and acceptor sites, and transcriptional termination sequences. Expression of recombinant proteins in insect cell culture systems (e.g., baculovirus) also offers a robust method for producing correctly folded and biologically functional proteins. Baculovirus systems for production of heterologous proteins in insect cells are well-known to those of skill in the art.
6.6 Methods of production

Provided herein are also methods of producing the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) and the anti-LILRB2/CD98hc bispecific antibodies disclosed herein. In some embodiments, the anti-CD98hc antibodies, fusion proteins, or the anti-LILRB2/CD98hc bispecific antibodies disclosed herein are comprised of more than one polypeptide chain, which can be produced separately or together. In some embodiments, methods provided herein produce at least one polypeptide chain of the bispecific antibodies disclosed herein. In some embodiments, methods provided herein produce all polypeptide chains of the bispecific antibodies disclosed herein.

The anti-CD98hc antibodies, fusion proteins, and the anti-LILRB2/CD98hc bispecific antibodies described herein can be produced and isolated using methods known in the art. Polyeptides can be synthesized, in whole or in part, using chemical methods (see, e.g., Caruthers (1980) . Nucleic Acids Res. Symp. Ser. 215; Horn (1980) ; and Banga, A.K., THERAPEUTIC PEPTIDES AND PROTEINS, FORMULATION, PROCESSING AND DELIVERY SYSTEMS (1995) Technomic Publishing Co., Lancaster, PA) . Peptide synthesis can be performed using various solid phase techniques (see, e.g., Roberge, Science 269: 202 (1995) ; Merrifield, Methods. Enzymol. 289: 3 (1997) ) and automated synthesis may be achieved, e.g., using the ABI 431A Peptide Synthesizer (Perkin Elmer) in accordance with the manufacturer’s instructions. Peptides can also be synthesized using combinatorial methodologies. Synthetic residues and polypeptides can be synthesized using a variety of procedures and methodologies known in the art (see, e.g., ORGANIC SYNTHESES COLLECTIVE VOLUMES, Gilman, et al., (Eds) John Wiley &Sons, Inc., NY) . Modified peptides can be produced by chemical modification methods (see, for example, Belousov, Nucleic Acids Res. 25: 3440 (1997) ; Frenkel, Free Radic. Biol. Med. 19: 373 (1995) ; and Blommers, Biochemistry 33: 7886 (1994) ) . Peptide sequence variations, derivatives, substitutions and modifications can also be made using methods such as oligonucleotide-mediated (site-directed) mutagenesis, alanine scanning, and PCR based mutagenesis. Site-directed mutagenesis (Carter et al., Nucl. Acids Res., 13: 4331 (1986) ; Zoller et al., Nucl. Acids Res. 10: 6487 (1987) ) , cassette mutagenesis (Wells et al., Gene 34: 315 (1985) ) , restriction selection mutagenesis (Wells et al., Philos. Trans. R. Soc. London SerA 317: 415 (1986) ) and other techniques can be performed on cloned DNA to produce invention peptide sequences, variants, fusions and chimeras, and variations, derivatives, substitutions and modifications thereof.

A variety of host-expression vector systems can be utilized to recombinantly express the bispecific antibodies described herein or one or more of their polypeptide chains. Suitable host cells for expression include prokaryotes, yeast cells, insect cells, or higher eukaryotic cells under the control of appropriate promoters. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts, as well as methods of protein production, including antibody production are well-known in the art. Such host-expression systems represent vehicles by which the coding sequences of the bispecific antibodies described herein can be produced and subsequently purified, but also represent cells which may, when transformed or transfected with the appropriate polynucleotide coding sequences, express the bispecific antibodies described herein in situ. These include, but are not limited to, microorganisms such as bacteria (e.g., E. coli and B. subtilis) transformed with recombinant bacteriophage DNA, plasmid DNA or cosmid DNA expression vectors containing coding sequences for the compounds described herein; yeast (e.g., Saccharomyces pichia) transformed with recombinant yeast expression vectors containing sequences encoding the compounds described herein; insect cell systems infected with recombinant virus expression vectors (e.g., baclovirus) containing the sequences encoding the compounds described herein; plant cell systems infected with recombinant virus expression vectors (e.g., cauliflower mosaic virus (CaMV) and tobacco mosaic virus (TMV) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing sequences encoding the molecules compounds described herein; or mammalian cell systems (e.g., COS, CHO, BHK, 293, 293T, 3T3 cells, lymphotic cells (see U.S. Pat. No. 5,807,715) , Per C. 6 cells (human retinal cells developed by Crucell) harboring recombinant expression constructs containing promoters derived from the genome of mammalian cells (e.g., metallothionein promoter) or from mammalian viruses (e.g., the adenovirus late promoter; the vaccinia virus 7.5K promoter) .

In bacterial systems, many expression vectors can be advantageously selected depending upon the use intended for the protein being expressed. For example, when a large quantity of such a protein is to be produced, for the generation of pharmaceutical compositions of the bispecific antibodies described herein, vectors which direct the expression of high levels of protein products that are readily purified can be desirable. Such vectors include, but are not limited, to the E. coli expression vector pUR278 (Ruther et al., (1983) , EMBO J. 2: 1791-1794) ; pIN vectors (Inouye et al., (1985) , Nucleic Acids Res. 13: 3101-3110; Van Heeke et al., (1989) , J. Biol. Chem. 24: 5503-5509) ; and the like. pGEX vectors can also be used to express polypeptides as fusion proteins with glutathione S-transferase (GST) . In general, such proteins are soluble and can easily be purified from lysed cells by adsorption and binding to a matrix glutathione-agarose beads followed by elution in the presence of free glutathione. The pGEX vectors are designed to include thrombin or factor Xa protease cleavage sites so that the cloned target gene product can be released from the GST moiety.

Useful expression vectors for eukaryotic hosts include, for example, vectors comprising expression control sequences from SV40, bovine papilloma virus, adenovirus, and cytomegalovirus. In mammalian host cells, a number of viral-based expression systems can be utilized. Examples of suitable mammalian host cell lines include, but are not limited to, COS-7 (monkey kidney-derived) , L-929 (murine fibroblast-derived) , C127 (murine mammary tumor-derived) , 3T3 (murine fibroblast-derived) , CHO (Chinese hamster ovary-derived) , HeLa (human cervical cancer-derived) , BHK (hamster kidney fibroblast-derived) , HEK-293 (human embryonic kidney-derived) cell lines and variants thereof. Mammalian expression vectors can comprise non-transcribed elements such as an origin of replication, a suitable promoter and enhancer linked to the gene to be expressed, and other 5’ or 3’ flanking non-transcribed sequences, and 5’ or 3’ non-translated sequences, such as necessary ribosome binding sites, a polyadenylation site, splice donor and acceptor sites, and transcriptional termination sequences. Expression of recombinant proteins in insect cell culture systems (e.g., baculovirus) also offers a robust method for producing correctly folded and biologically functional proteins. Baculovirus systems for production of heterologous proteins in insect cells are well-known to those of skill in the art. Autographa californica nuclear polyhedrosis virus (AcNPV) is used as a vector to express foreign genes.

In addition, a host cell strain can be chosen which modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products can be important for the function of the protein. For example, in certain embodiments, the antibodies described herein can be expressed as a single gene product (e.g., as a single polypeptide chain, i.e., as a polyprotein precursor) , requiring proteolytic cleavage by native or recombinant cellular mechanisms to form separate polypeptides of the bispecific antibodies described herein. The disclosure thus encompasses engineering a nucleic acid sequence to encode a polyprotein precursor molecule comprising the polypeptides of the bispecific antibodies described herein, which includes coding sequences capable of directing post translational cleavage of said polyprotein precursor. Post-translational cleavage of the polyprotein precursor results in the polypeptides of the bispecific antibodies described herein. The post translational cleavage of the precursor molecule comprising the polypeptides of the compounds described herein can occur in vivo (i.e., within the host cell by native or recombinant cell systems/mechanisms, e.g. furin cleavage at an appropriate site) or can occur in vitro (e.g. incubation of said polypeptide chain in a composition comprising proteases or peptidases of known activity and/or in a composition comprising conditions or reagents known to foster the desired proteolytic action) . Purification and modification of recombinant proteins is well known in the art such that the design of the polyprotein precursor can include a number of embodiments readily appreciated by a skilled artisan. Any known proteases or peptidases known in the art can be used for the described modification of the precursor molecule.

Different host cells have characteristic and specific mechanisms for the post-translational processing and modification of proteins and gene products. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the foreign protein expressed. To this end, eukaryotic host cells which possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the gene product may be used. Such mammalian host cells include but are not limited to CHO, VERY, BHK, HeLa, COS, MDCK, 293, 293T, 3T3, WI38, BT483, Hs578T, HTB2, BT20 and T47D, CRL7030 and Hs578Bst.

For long-term, high-yield production of recombinant proteins, stable expression is preferred. For example, cell lines which stably express compounds described herein can be engineered. Rather than using expression vectors which contain viral origins of replication, host cells can be transformed with DNA controlled by appropriate expression control elements (e.g., promoter, enhancer, sequences, transcription terminators, polyadenylation sites, etc. ) , and a selectable marker. Following the introduction of the foreign DNA, engineered cells can be allowed to grow for 1-2 days in an enriched media, and then are switched to a selective media. The selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which in turn can be cloned and expanded into cell lines. This method can advantageously be used to engineer cell lines which express the compounds described herein. Such engineered cell lines may be particularly useful in screening and evaluation of compounds that interact directly or indirectly with the compounds described herein.

A number of selection systems may be used, including but not limited to the herpes simplex virus thymidine kinase (Wigler et al., (1977) , Cell 11: 223-232) , hypoxanthine-guanine phosphoribosyltransferase (Szybalska et al., (1992) Bioessays 14: 495-500) , and adenine phosphoribosyltransferase (Lowy et al., (1980) , Cell 22: 817-823) genes can be employed in tk-, hgprt-or aprt-cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for the following genes: dhfr, which confers resistance to methotrexate (Wigler et al., (1980) PNAS 77: 3567-3570; O'Hare et al., (1981) PNAS, 78: 1527-1531) ; gpt, which confers resistance to mycophenolic acid (Mulligan et al., (1981) PNAS, 78: 2072-2076) ; neo, which confers resistance to the aminoglycoside G-418 (Tolstoshev (1993) , Ann. Rev. Pharmacol. Toxicol. 32: 573-596; Mulligan (1993) , Science 260: 926-932; and Morgan et al., (1993) , Ann. Rev. Biochem. 62: 191-217) and hygro, which confers resistance to hygromycin (Santerre et al., (1984) Gene 30: 147-156) . Methods commonly known in the art of recombinant DNA technology which can be used are described in Ausubel et al., (eds. ) , 1993, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley &Sons, NY; Kriegler, 1990, GENE TRANSFER AND EXPRESSION, A LABORATORY MANUAL, Stockton Press, NY; and in Chapters 12 and 13, Dracopoli et al., (eds) , 1994, CURRENT PROTOCOLS IN HUMAN GENETICS, John Wiley &Sons, NY.

The expression levels of antibodies described herein or their polypeptide chains can be increased by vector amplification (for a review, see Bebbington and Hentschel, The use of vectors based on gene amplification for the expression of cloned genes in mammalian cells in DNA cloning, Vol. 3 (Academic Press, New York, 1987) . When a marker in the vector system described herein is amplifiable, increase in the level of inhibitor present in culture of host cell will increase the number of copies of the marker gene. Since the amplified region is associated with the nucleotide sequence of a protein of interest, production of the protein of interest will also increase (Crouse et al., (1983) Mol. Cell. Biol. 3: 257-266) .

The host cell can be co-transfected with more than one expression vectors, each encoding a polypeptide chain of a bispecific antibody described herein. The vectors can contain identical selectable markers which enable equal expression of all polypeptides. Alternatively, a single vector can be used which encodes two or more polypeptides. The coding sequences for the polypeptides of compounds described herein can comprise cDNA or genomic DNA.

Once the anti-CD98hc antibodies, fusion proteins, and the anti-LILRB2/CD98hc bispecific antibodies described herein has been recombinantly expressed, it can be purified by any method known in the art for purification of polypeptides, polyproteins or antibodies (e.g., analogous to antibody purification schemes based on antigen selectivity) for example, by chromatography (e.g., ion exchange, affinity, particularly by affinity for the specific antigen (optionally after Protein A selection where the compound comprises an Fc domain (or portion thereof) ) , and sizing column chromatography) , centrifugation, differential solubility, or by any other standard technique for the purification of polypeptides or antibodies.

Provided herein are methods of producing anti-CD98hc antibodies, fusion proteins, and the anti-LILRB2/CD98hc bispecific antibodies described herein, the method comprising obtaining a cell described herein and expressing the polynucleotide described herein in said cell. In some embodiments, the method further comprises isolating and purifying a bispecific antibody or polypeptide chain described herein.

The bispecific antibodies described herein can be tested for binding to human CD98hc and/or LILRB2 by, for example, standard ELISA. Briefly, microtiter plates are coated with purified antigen, and then blocked with bovine serum albumin. Dilutions of antibody are added to each well and incubated. The plates are washed and incubated with secondary reagent (e.g., for human antibodies, a goat-anti-human IgG Fc-specific polyclonal reagent) conjugated to horseradish peroxidase (HRP) . After washing, the plates can be developed and analyzed by a spectrophotometer. Antibodies can be further tested by flow cytometry for binding to a cell line expressing human CD98hc and/or LILRB2, but not to a control cell line that does not express the target antigen. Briefly, the binding of antibodies can be assessed by incubating CD98hc and/or LILRB2 expressing CHO cells with the bispecific antibody provided herein. The cells can be washed, and binding can be detected with an anti-human IgG Ab. Flow cytometric analyses can be performed using a FACS can flow cytometry (Becton Dickinson, San Jose, CA) .

The bispecific antibodies provided herein can be further tested for reactivity with the target antigen (s) by Western blotting, and other methods known in the art for analyzing binding affinity, cross-reactivity, and binding kinetics of various bispecific antibodies described herein include, for example, biolayer interferometry (BLI) using, for example, Gator system (Probe Life) or the Octet-96 system (Sartorius AG) , or BIACORE^TM surface plasmon resonance (SPR) analysis using a BIACORE^TM 2000 SPR instrument (Biacore AB, Uppsala, Sweden) .

The practice of the invention employs, unless otherwise indicated, conventional techniques in molecular biology, microbiology, genetic analysis, recombinant DNA, organic chemistry, biochemistry, PCR, oligonucleotide synthesis and modification, nucleic acid hybridization, and related fields within the skill of the art. These techniques are described in the references cited herein and are fully explained in the literature. See, e.g., Maniatis et al., (1982) MOLECULAR CLONING: A LABORATORY MANUAL, Cold Spring Harbor Laboratory Press; Sambrook et al., (1989) , MOLECULAR CLONING: A LABORATORY MANUAL, Second Edition, Cold Spring Harbor Laboratory Press; Sambrook et al., (2001) MOLECULAR CLONING: A LABORATORY MANUAL, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY; Ausubel et al., CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley &Sons (1987 and annual updates) ; CURRENT PROTOCOLS IN IMMUNOLOGY, John Wiley &Sons (1987 and annual updates) Gait (ed. ) (1984) OLIGONUCLEOTIDE SYNTHESIS: A PRACTICAL APPROACH, IRL Press; Eckstein (ed. ) (1991) OLIGONUCLEOTIDES AND ANALOGUES: A PRACTICAL APPROACH, IRL Press; Birren et al., (eds. ) (1999) GENOME ANALYSIS: A LABORATORY MANUAL, Cold Spring Harbor Laboratory Press; Borrebaeck (ed. ) (1995) ; each of which is incorporated herein by reference in its entirety.
6.7 Pharmaceutical Compositions

Provided herein are also pharmaceutical compositions comprising the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein. In some embodiments, the pharmaceutical composition comprises a therapeutically effective amount of the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein and a pharmaceutically acceptable carrier. In some embodiments, pharmaceutical compositions disclosed herein are useful in treating a neurological disease or disorder.

In some embodiments, the pharmaceutical compositions provided herein comprise the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) provided herein. Pharmaceutically acceptable carriers that can be used in compositions provided herein include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. In some embodiments, the carrier is suitable for intravenous, intramuscular, subcutaneous, parenteral, spinal or epidermal administration (e.g., by injection or infusion) . Depending on the route of administration, the active ingredient (i.e., the bispecific antibodies) can be coated in a material to protect the active ingredient from the action of acids and other natural conditions that can inactivate the active ingredient.

Provided herein are also kits for preparation of pharmaceutical compositions having the bispecific antibodies disclosed herein. In some embodiments, the kit comprises the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein and a pharmaceutically acceptable carrier in one or more containers. In another embodiment, the kits can comprise the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein for administration to a subject. In specific embodiments, the kits comprise instructions regarding the preparation and/or administration of the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein.

Provided herein are also pharmaceutical compositions or formulations that improve the stability of the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein to allow for their long-term storage. In some embodiments, the pharmaceutical composition or formulation disclosed herein comprises: (a) the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , and/or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) disclosed herein disclosed herein; (b) a buffering agent; (c) a stabilizing agent; (d) a salt; (e) a bulking agent; and/or (f) a surfactant. In some embodiments, the pharmaceutical composition or formulation is stable for at least 1 month, at least 2 months, at least 3 months, at least 6 months, at least 1 year, at least 2 years, at least 3 years, at least 5 years or more. In some embodiments, the pharmaceutical composition or formulation is stable when stored at 4℃, 25℃, or 40℃.

Buffering agents useful in the pharmaceutical compositions or formulations disclosed herein can be a weak acid or base used to maintain the acidity (pH) of a solution near a chosen value after the addition of another acid or base. Suitable buffering agents can maximize the stability of the pharmaceutical formulations by maintaining pH control of the formulation. Suitable buffering agents can also ensure physiological compatibility or optimize solubility. Rheology, viscosity and other properties can also depend on the pH of the formulation. Common buffering agents include, but are not limited to, histidine, citrate, succinate, acetate and phosphate. In some embodiments, a buffering agent comprises histidine (e.g., L-histidine) with isotonicity agents and potentially pH adjustment with an acid or a base known in the art. In certain embodiments, the buffering agent is L-histidine. In certain embodiments, the pH of the formulation is maintained between about 2 and about 10, or between about 4 and about 8.

Stabilizing agents are added to a pharmaceutical product to stabilize that product. Such agents can stabilize proteins in different ways. Common stabilizing agents include, but are not limited to, amino acids such as glycine, alanine, lysine, arginine, or threonine, carbohydrates such as glucose, sucrose, trehalose, rafftnose, or maltose, polyols such as glycerol, mannitol, sorbitol, cyclodextrins or destrans of any kind and molecular weight, or PEG. In some embodiments, the stabilizing agent is chosen to maximize the stability of FIX polypeptide in lyophilized preparations. In certain embodiments, the stabilizing agent is sucrose and/or arginine.

Bulking agents can be added to a pharmaceutical composition or formulation to add volume and mass to the product, thereby facilitating precise metering and handling thereof. Common bulking agents include, but are not limited to, lactose, sucrose, glucose, mannitol, sorbitol, calcium carbonate, or magnesium stearate.

Surfactants are amphipathic substances with lyophilic and lyophobic groups. A surfactant can be anionic, cationic, zwitterionic, or nonionic. Examples of nonionic surfactants include, but are not limited to, alkyl ethoxylate, nonylphenol ethoxylate, amine ethoxylate, polyethylene oxide, polypropylene oxide, fatty alcohols such as cetyl alcohol or oleyl alcohol, cocamide MEA, cocamide DEA, polysorbates, or dodecyl dimethylamine oxide. In some embodiments, the surfactant is polysorbate 20 or polysorbate 80.

The pharmaceutical compositions disclosed herein can further comprise one or more of a buffer system, a preservative, a tonicity agent, a chelating agent, a stabilizer and/or a surfactant, as well as various combinations thereof. The use of preservatives, isotonic agents, chelating agents, stabilizers and surfactants in pharmaceutical compositions is well-known to the skilled person. Reference may be made to REMINGTON: THE SCIENCE AND PRACTICE OF PHARMACY, 19^th edition, 1995.

In some embodiments, the pharmaceutical composition is an aqueous formulation. Such a formulation is typically a solution or a suspension, but can also include colloids, dispersions, emulsions, and multi-phase materials. The term “aqueous formulation” is defined as a formulation comprising at least 50%w/w water. Likewise, the term “aqueous solution” is defined as a solution comprising at least 50 %w/w water, and the term “aqueous suspension” is defined as a suspension comprising at least 50 %w/w water.

In some embodiments, the pharmaceutical compositions disclosed herein are freeze-dried, to which the physician or the patient adds solvents and/or diluents prior to use.

Pharmaceutical compositions disclosed herein can also include a pharmaceutically acceptable antioxidant. Examples of pharmaceutically acceptable antioxidants include: (1) water soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA) , butylated hydroxytoluene (BHT) , lecithin, propyl gallate, alpha-tocopherol, and the like; and (3) metal chelating agents, such as citric acid, ethylenediamine tetraacetic acid (EDTA) , sorbitol, tartaric acid, phosphoric acid, and the like.

Examples of suitable aqueous and nonaqueous carriers that can be employed in the pharmaceutical compositions or formulations described herein include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol, and the like) , and suitable mixtures thereof, vegetable oils, such as olive oil, and injectable organic esters, such as ethyl oleate. Proper fluidity can be maintained, for example, by the use of coating materials, such as lecithin, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants.

These compositions can also contain adjuvants such as preservatives, wetting agents, emulsifying agents and dispersing agents. Prevention of presence of microorganisms can be ensured both by sterilization procedures, supra, and by the inclusion of various antibacterial and antifungal agents, for example, paraben, chlorobutanol, phenol sorbic acid, and the like. It can also be desirable to include isotonic agents, such as sugars, sodium chloride, and the like into the compositions. In addition, prolonged absorption of the injectable pharmaceutical form can be brought about by the inclusion of agents which delay absorption such as aluminum monostearate and gelatin.

Pharmaceutically acceptable carriers include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. The use of such media and agents for pharmaceutically active substances is known in the art. In some embodiments, provided herein is a pharmaceutical composition comprising the bispecific antibodies or cells provided herein wherein the composition is suitable for local administration.

Pharmaceutical compositions or formulations typically must be sterile and stable under the conditions of manufacture and storage. The composition can be formulated as a solution, microemulsion, liposome, or other ordered structure suitable to high drug concentration. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like) , and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. In many cases, the compositions can include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, or sodium chloride in the composition. Prolonged absorption of the injectable compositions can be brought about by including in the composition an agent that delays absorption, for example, monostearate salts and gelatin.

Sterile injectable solutions can be prepared by incorporating the active compound in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by sterilization microfiltration. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated herein. In the case of sterile powders for the preparation of sterile injectable solutions, some methods of preparation are vacuum drying and freeze-drying (lyophilization) that yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

The amount of active ingredient which can be combined with a carrier material in the pharmaceutical compositions or formulations disclosed herein can vary. In some embodiments, the amount of active ingredient which can be combined with a carrier material is the amount that produces a therapeutic effect. Generally, out of one hundred percent, this amount will range from about 0.01 percent to about ninety-nine percent of active ingredient, from about 0.1 percent to about 70 percent, or from about 1 percent to about 30 percent of active ingredient in combination with a pharmaceutically acceptable carrier.

The pharmaceutical compositions disclosed herein can be prepared with carriers that protect the active ingredient against rapid release, such as a controlled release formulation, including implants, transdermal patches, and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and poly lactic acid. Many methods for the preparation of such formulations are patented or generally known to those skilled in the art. See. e.g., SUSTAINED AND CONTROLLED RELEASE DRUG DELIVERY SYSTEMS, J. R. Robinson, ed., Marcel Dekker, Inc., New York, 1978.
6.8 Methods and Uses

The anti-CD98hc antibodies provided herein are capable of crossing BBB. Accordingly, provided herein are methods of uses of the anti-CD98hc antibodies disclosed herein to deliver an effector moiety across the BBB, wherein methods comprising administering to the subject a conjugate comprising the anti-CD98hc antibodies provided herein linked to the effector moiety. As The anti-CD98hc antibodies provided herein, conjugates (e.g., fusion proteins) , and bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) provided herein can advantageously be transported across BBB. Accordingly, provided herein are methods of administering or transporting anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) provided herein across the BBB of a subject comprising administering to the subject anti-CD98hc antibodies provided herein, conjugates (e.g., fusion proteins) , or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) by, for example, oral administration or intravenous injection.

In some embodiments, methods provided herein comprise administering the anti-CD98hc antibodies, conjugates (e.g., fusion proteins) , or bispecific antibodies (e.g., anti-LILRB2/CD98hc bispecific antibodies) provided herein to a subject in need thereof. In some embodiments, the subject is a mammal. In some embodiments, the subject is a human. A human subject who needs the treatment can be a human subject having, at risk for, or suspected of having a disease. A subject having a disease can be identified by routine medical examination, e.g., a physical examination, a laboratory test, an organ functional test, a CT scan, or an ultrasound. A subject suspected of having any of such a disease can show one or more symptoms of the disease. Signs and symptoms for diseases, e.g., autoimmune and inflammatory diseases, are well known to those of ordinary skill in the art. A subject at risk for the disease can be a subject having one or more of the risk factors. In some embodiments, the human subject has a neurological disease or disorder. In some embodiments, the human subject is at risk for having a neurological disease or disorder. In some embodiments, the human subject is suspected of having a neurological disease or disorder.

In view of the ability of therapeutic conjugates provided herein, namely, the conjugates having an anti-CD98hc disclosed herein linked to a therapeutic effector moiety to be transported across a BBB, they can be used to treat a neurological disease or disorder. In some embodiments, provided herein are methods of treating a neurological disease or disorder in a subject comprises administering to the subject a therapeutically effective amount of a conjugate disclosed herein having a therapeutic effector moiety (e.g., anti-LILRB2/CD98hc bispecific antibodies) . The neurological disease or disorder can be, for example, a neuropathy disorder, a neurodegenerative disease, cancer, an ocular disease disorder, a seizure disorder, a lysosomal storage disease, amyloidosis, a viral or microbial disease, ischemia, a behavioral disorder, or CNS inflammation. The neurological disease or disorder can be, for example, a neurodegenerative disease (such as Lewy body disease, postpoliomyelitis syndrome, Shy-Drager syndrome, olivopontocerebellar atrophy, Parkinson’s disease, Gaucher disease, multiple system atrophy, striatonigral degeneration, spinocerebellar ataxia, spinal muscular atrophy) , a tauopathy (such as Alzheimer’s disease and supranuclear palsy) , a prion disease (such as bovine spongiform encephalopathy, scrapie, Creutzfeldt-Jakob disease, kuru, disease, chronic wasting disease, and fatal familial insomnia) , bulbar palsy, motor neuron disease, a nervous system heterodegenerative disorder (such as Canavan disease, Huntington's disease, neuronal ceroid-lipofuscinosis, Alexander’s disease, Tourette's syndrome, Menkes kinky hair syndrome, Cockayne syndrome, Hallervorden-Spatz syndrome, Lafora disease, Rett syndrome, hepatolenticular degeneration, Lesch-Nyhan syndrome, and Unverricht-Lundborg syndrome) , dementia (such as Pick's disease and spinocerebellar ataxia) , cancer of the CNS and/or brain (such as glioblastoma or brain metastases resulting from cancer elsewhere in the body) , stroke, muscular dystrophy (MD) , multiple sclerosis (MS) , amyotrophic lateral sclerosis (ALS) , limbic-predominant age-related TDP-43 encephalopathy (LATE) , cystic fibrosis, Angelman syndrome, Liddle syndrome, Paget’s disease, addictive disorder, or traumatic brain injury. In some embodiments, the neurological disease or disorder is a neurodegenerative disease. In some embodiments, the neurological disease or disorder is Alzheimer’s disease.

The anti-CD98hc antibodies and conjugates (e.g., bispecific antibodies) provided herein can be used for detection and imaging purposes, especially within the CNS. In some embodiments, anti-CD98 antibodies described herein can be conjugated with various effector moieties, such as fluorescent dyes or radioactive isotopes. These conjugates leverage the BBB-penetrating ability of anti-CD98 antibodies to deliver imaging agents into the brain, facilitating the detection and visualization of disease processes in the CNS. Fluorescently labeled anti-CD98 antibodies can also be used for in vivo imaging within the brain. Exemplary fluorescent dyes include Alexa Fluor 680, Cy5, and IRDye 800CW. Additionally, anti-CD98 antibodies can also be conjugated with radioactive isotopes such as technetium-99m (99mTc) , iodine-131 (131I) , fluorine-18 (18F) or Carbon-11 (11C) . These radiolabeled conjugates enable the use of nuclear imaging techniques like single-photon emission computed tomography (SPECT) or positron emission tomography (PET) .

In some embodiments, the conjugates comprise an anti-CD98 antibody or antigen-binding fragment disclosed herein and an antibody for a CNS antigen or a brain antigen, which can be used for the detection of such antigen in CNS. In some embodiments, a method of detecting an antigen in the CNS (e.g., brain) of a subject comprises administering a conjugate described herein comprising an anti-CD98hc antibody and an antigen in the CNS antigen, wherein the conjugate is labeled with an imaging moiety such as a fluorescent label or a radioactive isotope. Such methods can further comprise, e.g., performing PET imaging on the subject.

The anti-CD98hc antibodies and conjugates (e.g., bispecific antibodies) provided herein can be used for prognostic, diagnostic, monitoring, and/or screening applications, including in vivo applications well known and standard to the skilled artisan and based on the present description. For prognostic applications, conjugates can carry biomarkers that indicate disease progression or treatment response, enabling early prediction of outcomes. Diagnostic applications involve using conjugates with imaging agents, such as fluorescent dyes or radiolabeled isotopes, to visualize and detect neurological conditions, including brain tumors and neurodegenerative diseases, through non-invasive imaging techniques like PET or SPECT. Monitoring applications include the use of these conjugates to track disease status and therapeutic efficacy over time by delivering agents that can be periodically detected and measured within the brain. Screening applications involve the use of these conjugates in high-throughput assays to identify patients at risk for CNS disorders or to discover new therapeutic targets.

In some embodiments, anti-CD98hc antibodies and conjugates (e.g., bispecific antibodies) provided herein are not significantly toxic. For example, anti-CD98hc antibodies and conjugates (e.g., bispecific antibodies) provided herein are not significantly toxic to an organ of a human, e.g., one or more of the liver, kidney, brain, lungs, and heart, as determined, e.g., in clinical trials. In some embodiments, the bispecific antibodies disclosed herein do not significantly trigger an undesirable immune response, e.g., autoimmunity or inflammation.

Actual dosage levels of the active ingredients (e.g., the bispecific antibodies provided herein) in the pharmaceutical compositions described herein can be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration, without being toxic to the patient. The selected dosage level will depend upon a variety of pharmacokinetic factors including the activity of the particular compositions described herein, the route of administration, the time of administration, the rate of excretion, the duration of the treatment, other drugs, compounds and/or materials used in combination with the particular compositions employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts.

The anti-CD98hc antibodies, conjugates (e.g., bispecific antibodies) , or pharmaceutical compositions provided herein can be administered to a subject by any methods known in the art, including, but not limited to, pleural administration, intravenous administration, subcutaneous administration, intranodal administration, intratumoral administration, intramuscular administration, intradermal administration, intrathecal administration, intrapleural administration, intraperitoneal administration, intracranial administration, spinal or other parenteral routes of administration, for example by injection or infusion, or direct administration to the thymus. The phrase “parenteral administration” as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal, epidural and intrastemal injection and infusion. In some embodiments, subcutaneous administration is adopted. In some embodiments, intravenous administration is adopted. In some embodiments, oral administration is adopted. In some embodiments, intrathecal administration is adopted. In some embodiments, intranasal administration is adopted. In some embodiments, transdermal administration is adopted. In some embodiments, intra parenchymal administration is adopted. In some embodiments, intramuscular administration is adopted.

The anti-CD98hc antibodies, conjugates (e.g., bispecific antibodies) or pharmaceutical compositions provided herein can be administered with medical devices known in the art. For example, in some embodiments, a needleless hypodermic injection device can be used, such as the devices disclosed in U.S. Patent Nos. 5,399,163; 5,383,851; 5,312,335; 5,064,413; 4,941,880; 4,790,824; or 4,596,556. Examples of well-known implants and modules for use described herein include: U.S. Patent No. 4,487,603, which discloses an implantable micro-infusion pump for dispensing medication at a controlled rate; U.S. Patent No. 4,486,194, which discloses a therapeutic device for administering medicaments through the skin; U.S. Patent No. 4,447,233, which discloses a medication infusion pump for delivering medication at a precise infusion rate; U.S. Patent No. 4,447,224, which discloses a variable flow implantable infusion apparatus for continuous drug delivery; U.S. Patent No. 4,439,196, which discloses an osmotic drug delivery system having multi-chamber compartments; and U.S. Patent No. 4,475,196, which discloses an osmotic drug delivery system. These patents are incorporated herein by reference. Many other such implants, delivery systems, and modules are known to those skilled in the art.

The anti-CD98hc antibodies, conjugates (e.g., bispecific antibodies) , or pharmaceutical compositions described herein can be administered with another treatment, such as a standard of care treatment. The additional therapy can be administered prior to, concurrently with, or subsequent to administration of the conjugates (e.g., bispecific antibodies) or pharmaceutical compositions described herein. Combined administration can include co-administration, either in a single pharmaceutical formulation or using separate formulations, or consecutive administration in either order but generally within a time period such that all active agents can exert their biological activities simultaneously. A person skilled in the art can readily determine appropriate regimens for administering a pharmaceutical composition described herein and an additional therapy in combination, including the timing and dosing of an additional agent to be used in a combination therapy, based on the needs of the subject being treated.
6.9 Exemplified Embodiments

Embodiment 1: An antibody or antigen-binding fragment thereof that specifically binds human CD98 heavy chain (CD98hc) , comprising (a) a heavy chain variable region (VH) comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 25, 26 and 27, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a light chain variable region (VL) comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 28, 29, and 30, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 2: The antibody or antigen-binding fragment of Embodiment 1, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 25, 26, 27, 28, 29, and 30, respectively.

Embodiment 3: The antibody or antigen-binding fragment of Embodiment 1, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 5; and/or
(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 6.

Embodiment 4: The antibody or antigen-binding fragment of Embodiment 3 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 5 and 6, respectively.

Embodiment 5: The antibody or antigen-binding fragment of any one of Embodiments 1 to 4 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 6: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 31, 32 and 33, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 34, 35, and 36, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 7: The antibody or antigen-binding fragment of Embodiment 6, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 31, 32, 33, 34, 35, and 36, respectively.

Embodiment 8: The antibody or antigen-binding fragment of Embodiment 6, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 7; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 8.

Embodiment 9: The antibody or antigen-binding fragment of Embodiment 8 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 7 and 8, respectively.

Embodiment 10: The antibody or antigen-binding fragment of any one of Embodiments 6 to 9 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 11: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 37, 38 and 39, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 40, 41, and 42, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 12: The antibody or antigen-binding fragment of Embodiment 11, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 37, 38, 39, 40, 41, and 42, respectively.

Embodiment 13: The antibody or antigen-binding fragment of Embodiment 11, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 9; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 10.

Embodiment 14: The antibody or antigen-binding fragment of Embodiment 13 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 9 and 10, respectively.

Embodiment 15: The antibody or antigen-binding fragment of any one of Embodiments 11 to 14 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 16: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 43, 44 and 45, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 46, 47, and 48, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 17: The antibody or antigen-binding fragment of Embodiment 16, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 43, 44, 45, 46, 47, and 48, respectively.

Embodiment 18: The antibody or antigen-binding fragment of Embodiment 16, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 11; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 12.

Embodiment 19: The antibody or antigen-binding fragment of Embodiment 18 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 11 and 12, respectively.

Embodiment 20: The antibody or antigen-binding fragment of any one of Embodiments 16 to 19 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 21: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 49, 50 and 51, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 52, 53, and 54, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 22: The antibody or antigen-binding fragment of Embodiment 21, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 49, 50, 51, 52, 53, and 54, respectively.

Embodiment 23: The antibody or antigen-binding fragment of Embodiment 21, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 49, 118, 51, 52, 53, and 54, respectively.

Embodiment 24: The antibody or antigen-binding fragment of Embodiment 21, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 13 and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 14.

Embodiment 25: The antibody or antigen-binding fragment of Embodiment 24 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 13 and 14, respectively.

Embodiment 26: The antibody or antigen-binding fragment of any one of Embodiments 21 to 25 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 27: The antibody or antigen-binding fragment of Embodiment 26 that is a humanized antibody or antigen-binding fragment.

Embodiment 28: The antibody or antigen-binding fragment of Embodiment 27, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110, and 137; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 103 or 105.

Embodiment 29: The antibody or antigen-binding fragment of Embodiment 28 comprising a VL and a VH having the amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; or (6) SEQ ID NOs: 137 and 103, respectively.

Embodiment 30: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 55, 56 and 57, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 58, 59, and 60, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 31: The antibody or antigen-binding fragment of Embodiment 30, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 55, 56, 57, 58, 59, and 60, respectively.

Embodiment 32: The antibody or antigen-binding fragment of Embodiment 30, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 15; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 16.

Embodiment 33: The antibody or antigen-binding fragment of Embodiment 32 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 15 and 16, respectively.

Embodiment 34: The antibody or antigen-binding fragment of any one of Embodiment 30 to 33 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 35: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 61, 62 and 63, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 64, 65, and 66, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 36: The antibody or antigen-binding fragment of Embodiment 35, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 61, 62, 63, 64, 65, and 66, respectively.

Embodiment 37: The antibody or antigen-binding fragment of Embodiment 35, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 17; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 18.

Embodiment 38: The antibody or antigen-binding fragment of Embodiment 37 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 17 and 18, respectively.

Embodiment 39: The antibody or antigen-binding fragment of any one of Embodiments 35 to 38 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 40: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 67, 68 and 69, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 70, 71, and 72, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 41: The antibody or antigen-binding fragment of Embodiment 40, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 67, 68, 69, 70, 71, and 72, respectively.

Embodiment 42: The antibody or antigen-binding fragment of Embodiment 40, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 19; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 20.

Embodiment 43: The antibody or antigen-binding fragment of Embodiment 42 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 19 and 20, respectively.

Embodiment 44: The antibody or antigen-binding fragment of any one of Embodiments 40 to 43 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 45: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 73, 74 and 75, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 76, 77, and 78, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 46: The antibody or antigen-binding fragment of Embodiment 45, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 73, 74, 75, 76, 77, and 78, respectively, or SEQ ID NOs: 73, 74, 119, 76, 77, and 78, respectively.

Embodiment 47: The antibody or antigen-binding fragment of Embodiment 45, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 21; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 22.

Embodiment 48: The antibody or antigen-binding fragment of Embodiment 47 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 21 and 22, respectively.

Embodiment 49: The antibody or antigen-binding fragment of any one of Embodiments 45 to 48 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 50: The antibody or antigen-binding fragment of Embodiment 49 that is a humanized antibody or antigen-binding fragment.

Embodiment 51: The antibody or antigen-binding fragment of Embodiment 50, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to SEQ ID NO: 113.

Embodiment 52: The antibody or antigen-binding fragment of Embodiment 51 comprising a VL and a VH having the amino acid sequences of (1) SEQ ID NOs: 112 and 113, respectively; (2) SEQ ID NOs: 114 and 113, respectively; or (3) SEQ ID NOs: 116 and 113, respectively.

Embodiment 53: An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising (a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 79, 80 and 81, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and (b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 82, 83, and 84, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.

Embodiment 54: The antibody or antigen-binding fragment of Embodiment 53, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 79, 80, 81, 82, 83, and 84, respectively.

Embodiment 55: The antibody or antigen-binding fragment of Embodiment 53, comprising:
(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity
to the amino acid sequence of SEQ ID NO: 23; and/or (b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 24.

Embodiment 56: The antibody or antigen-binding fragment of Embodiment 55 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 23 and 24, respectively.

Embodiment 57: The antibody or antigen-binding fragment of any one of Embodiments 53 to 56 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.

Embodiment 58: The antibody or antigen-binding fragment of any one of Embodiments 1 to 57 that is selected from the group consisting of a Fab, a Fab’ , a F (ab’ ) 2, a Fv, a scFv, a (scFv) 2, a single domain antibody (sdAb) , and a heavy chain antibody (HCAb) .

Embodiment 59: The antibody or antigen-binding fragment of Embodiment 58 that is an scFv.

Embodiment 60: The antibody or antigen-binding fragment of Embodiment 59, wherein the scFv comprises from N terminus to C terminus, the VH, a linker, and the VL.

Embodiment 61: The antibody or antigen-binding fragment of Embodiment 59, wherein the scFv comprises from N terminus to C terminus, the VL, a linker, and the VH.

Embodiment 62: The antibody or antigen-binding fragment of Embodiment 60 or 61, wherein the linker has an amino acid sequence selected from the group consisting of SEQ ID NOs: 130-132.

Embodiment 63: The antibody or antigen-binding fragment of any one of Embodiments 1 to 57 that is an IgG1 antibody, an IgG2 antibody, an IgG3 antibody, or an IgG4 antibody.

Embodiment 64: An antibody or antigen-binding fragment thereof that competes with the antibody or antigen-binding fragment of any one of Embodiments 1 to 63 for binding to human CD98hc.

Embodiment 65: The antibody or antigen-binding fragment of any one of Embodiments 1 to 64 that is a bispecific antibody or a multispecific antibody.

Embodiment 66: The antibody or antigen-binding fragment of any one of Embodiments 1 to 65 that is a monoclonal antibody or antigen-binding fragment.

Embodiment 67: The antibody or antigen-binding fragment of any one of Embodiments 1 to 66, wherein the antibody or antigen binding fragment is an internalizing antibody or antigen binding fragment.

Embodiment 68: The antibody or antigen-binding fragment of any one of Embodiments 1 to 67, wherein the antibody or antigen binding fragment can cross the blood brain barrier (BBB) .

Embodiment 69: The antibody or antigen-binding fragment of any one of Embodiments 1 to 68, wherein the antibody or antigen binding fragment does not inhibit leucine uptake.

Embodiment 70: A polynucleotide encoding a polypeptide of the antibody or antigen-binding fragment of any one of Embodiments 1 to 69.

Embodiment 71: A vector comprising the polynucleotide of Embodiment 70.

Embodiment 72: A host cell comprising the polynucleotide of Embodiment 70, or the vector of Embodiment 71.

Embodiment 73: A method of making an antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising culturing the cell of Embodiment 72 under conditions that allow expression of the antibody or antibody fragment.

Embodiment 74: The method of Embodiment 73 that comprises isolating the antibody from the culture.

Embodiment 75: A conjugate comprising the antibody or antigen-binding fragment of any one of Embodiments 1 to 69 linked to an effector moiety.

Embodiment 76: The conjugate of Embodiment 75, wherein the effector moiety is selected from the group consisting of drugs for neurological diseases or disorders, neurotrophic factors, growth factors, enzymes, cytotoxic agents and imaging agents.

Embodiment 77: A method of delivering an effector moiety across BBB in a subject comprising administering to a subject a conjugate comprising the antibody or antigen-binding fragment of any one of Embodiments 1 to 69 linked to the effector moiety.

Embodiment 78: A fusion protein comprising the antibody or antigen-binding fragment of any one of Embodiments 1 to 69 linked to a second antibody or antigen-binding fragment that specifically binds to a central nervous system (CNS) antigen.

Embodiment 79: The fusion protein of Embodiment 78, wherein the CNS antigen is selected from the group consisting of alpha-synuclein, amyloid precursor protein (APP) , amyloid-beta (Aβ) , apolipoprotein E (ApoE) , apolipoprotein E4 (ApoE4) , ATP-binding cassette sub-family A member 1 (ABCA1) , ATP-binding cassette sub-family A member 7 (ABCA7) , beta-secretase 1 (BACE1) , caspase 6, CD20, CD33 (Siglec3) , death receptor 6 (DR6) , disialoganglioside (GD2) , epidermal growth factor (EGF) , epidermal growth factor receptor (EGFR) , epidermal growth factor receptor 2 (EGFR2/HER2) , gamma secretase, glycoprotein nonmetastatic melanoma protein B (GPNMB) , HLA-DR1, HLA-DR5, huntingtin, IL-34, IL1RAP, interleukin-13 receptor alpha 2 (IL-13Rα2) , leucine-rich repeat kinase 2 (LRRK2) , LILRB2, matrix metalloproteinases (MMPs) , membrane spanning 4-domains A4A (MS4A4A) , membrane spanning 4-domains A4E (MS4A4E) , membrane spanning 4-domains A 6A (MS4A6A) , p-glucocerebrosidase (GCase or GBA) , p75 neurotrophin receptor (p75NTR) , parkin, paired immunoglobin like type 2 receptor alpha (PILRA) , phosphorylated Tau, prion protein (PrP) , presenilin 1, presenilin 2, progranulin (PGRN) , prosaposin (PSAP) , sialic acid binding Ig-like lectin 11 (Siglec11) , sialic acid binding Ig-like lectin 5 (Siglec5) , sialic acid binding Ig-like lectin 7 (Siglec7) , sialic acid binding Ig-like lectin 9 (Siglec9) , sortilin (SORT) , sphingolipids, Tau protein, transmembrane protein 106B (TMEM106b) , triggering receptor expressed on myeloid cells 2 (TREM2) , TXNRD1, and ubiquitin protein ligase E3A (UBE3A) .

Embodiment 80: The fusion protein of Embodiment 78 or 79, that is a bispecific antibody.

Embodiment 81: The fusion protein of Embodiment 80 wherein the bispecific antibody comprises an IgG that specifically binds to the CNS antigen and an scFv that specifically binds to CD98hc.

Embodiment 82: The fusion protein of Embodiment 81, wherein the scFv is linked to the C terminus of a heavy chain of the IgG.

Embodiment 83: The fusion protein of any one of Embodiments 80 to 82, wherein the CNS antigen is LILRB2.

Embodiment 84: The fusion protein of Embodiment 83, wherein the antibody that specifically binds to LIBRB2 comprises a VH having VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 122, 123 and 124, respectively, and a VL having VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 125, 126, and 127 respectively.

Embodiment 85: The fusion protein of Embodiment 83, wherein the antibody that specifically binds to LIBRB2 comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 120 and 121, respectively.

Embodiment 86: A pharmaceutical composition comprising a therapeutically effective amount of the fusion protein of any one of Embodiments 78 to 85, and a pharmaceutically acceptable carrier.

Embodiment 87: A method of treating a neurological disease or disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the fusion protein of any one of Embodiments 78 to 85.

Embodiment 88: The method of Embodiment 87, wherein the neurological disease or disorder is a neurodegenerative disease.

Embodiment 89: The method of Embodiment 87 or 88, further comprising administering an additional therapy to the subject.

Embodiment 90: The method of any one of Embodiments 87 to 89, wherein the subject is a human.

Embodiment 91: Use of fusion protein of any one of Embodiments 78 to 85 for treating a neurological disease or disorder.

Embodiment 92: Use of fusion protein of any one of Embodiments 78 to 85 for manufacture of a medicament for a neurological disease or disorder.

Embodiment 93: Use of Embodiment 91 or 92, wherein the neurological disease is a neurodegenerative disease.

Embodiment 94: A bispecific antibody for CD98hc and LILBR2, comprising (1) a first peptide chain (HC1) comprising, from N-terminus to C-terminus, VH1 and a first CH region, and a scFv; (2) a second peptide chain (HC2) comprising, from N-terminus to C-terminus, VH1 and a second CH region; and (3) a third peptide chain (LC) comprising, from N-terminus to C-terminus, VL1 and a CL region; wherein (i) the VH1 and VL1 have the amino acid sequences of SEQ ID NOs: 120 and 121, respectively; and (ii) the scFv comprises VH2 and VL2 having the amino acid sequences of (1) SEQ ID NOs: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively; or humanized versions thereof.

Embodiment 95: The bispecific antibody of Embodiment 94, wherein the VH2 and VL2 have amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.

Embodiment 96: The bispecific antibody of Embodiment 94, wherein the scFv has at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-101 and 138.

Embodiment 97: The bispecific antibody of any one of Embodiments 94 to 96, wherein the CL region is Cκ.

Embodiment 98: The bispecific antibody of any one of Embodiments 94 to 97, wherein the first CH region further has T350V, L351Y, F405A, and Y407V substitutions and the second CH region has T350V, T366L, K392L, and T394W substitutions.

Embodiment 99: The bispecific antibody of any one of Embodiments 94 to 97, wherein the first CH region further has T366W substitution, and the second CH region further has T366S, L368A, and Y407V substitutions.

Embodiment 100: The bispecific antibody of Embodiment 98 or 99, wherein the first and second CH regions further have L234A, L235A, and D266S substitutions (AAS mutations) , or M252Y, S254T, and T256E (YTE mutations) , or both AAS mutations and YTE mutations.

Embodiment 101: The bispecific antibody of Embodiment 98 or 99, wherein the second CH region further has H435R and Y436F substitutions.

Embodiment 102: The bispecific antibody of Embodiment 94, wherein the HC1, HC2, and LC are at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to amino acid sequences of (1) SEQ ID NOs: 85, 86, and 87, respectively; (2) SEQ ID NOs: 88, 86, and 87, respectively; (3) SEQ ID NOs: 89, 86, and 87, respectively; (4) SEQ ID NOs: 90, 86, and 87, respectively; or (5) SEQ ID NOs: 91, 86, and 87, respectively.

Embodiment 103: A polynucleotide or a plurality of polynucleotide that encodes or collectively encode the three peptide chains of the bispecific antibody of any one of Embodiments 94 to 102.

Embodiment 104: A host cell comprising the polynucleotide or plurality of nucleotide of Embodiment 103.

Embodiment 105: A method of making a bispecific antibody that specifically binds human CD98hc, comprising culturing the cell of Embodiment 104 under conditions that allow expression of the bispecific antibody.

Embodiment 106: The method of Embodiment 105 that comprises isolating the antibody from the culture.

Embodiment 107: A pharmaceutical composition comprising a therapeutically effective amount of the bispecific antibody of any one of Embodiments 94 to 102, and a pharmaceutically acceptable carrier.

Embodiment 108: A method of treating a neurological disease or disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the bispecific antibody of any one of Embodiments 94 to 102.

Embodiment 109: The method of Embodiment 108, wherein the neurological disease or disorder is a neurodegenerative disease.

Embodiment 110: The method of Embodiment 108 or 109, further comprising administering an additional therapy to the subject.

Embodiment 111: The method of any one of Embodiments 108 to 110, wherein the subject is a human.

Embodiment 112: Use of conjugate of any one of Embodiments 94 to 102 for treating a neurological disease or disorder.

Embodiment 113: Use of conjugate of any one of Embodiments 94 to 102 for manufacture of a medicament for a neurological disease or disorder.

Embodiment 114: Use of Embodiment 112 or 113, wherein the neurological disease or disorder is a neurodegenerative disease.
6.10 Experimental

The examples provided below are for purposes of illustration only, which are not intended to be limiting unless otherwise specified. Thus, the invention should in no way be construed as being limited to the following examples, but rather, should be construed to encompass any and all variations which become evident as a result of the teaching provided herein.
6.10.1 Example 1: Antigen preparation (human CD98 ECD)

His-tagged human and cynomolgus macaque (cyno) CD98 heavy chain extracellular domains (ECD) were generated following the method described below. The cDNA of human and cynomolgus macaque extracellular domain of CD98 variants were cloned to mammalian expression vector with C-terminal His tag. For protein expression, CD98 ECD were expressed in expi293F cells. 4 days after transfection, culture supernatants were collected by centrifugation and filtered using 0.2 μm filtration unit. For protein purification, the supernatant was loaded onto balanced Ni-NTA resin (Qiagen 30250) . The resin was washed with washing buffer containing 20 mM imidazole, following by protein eluted with elution buffer with 400 mM imidazole. The eluents were concentrated and loaded to size-exclusion chromatography (Superdex 200 Increase 10/300 GL, Cytiva) in dPBS buffer. The peak fractions were collected and followed by an endotoxin removal step (ToxinSensor^TM Single Test Kit, GenScript, #L00859) . The purified product was split into aliquots, flash-frozen in liquid nitrogen and stored at -80℃ for immunization.
6.10.2 Example 2: Production of cell line overexpressing human or cyno CD98hc

The cells used for hybridoma screening were prepared as follows: HEK293 or CHO cells were transfected with pLenti-CMV constructs to generate cell line stably expressing human CD98hc (SEQ ID NO: 3) or Cyno CD98hc (SEQ ID NO: 4) , respectively. In brief, Lentiviral constructs were used to express human or cyno CD98hc with puromycin selection. Lentivirus was generated from transfection of 293T cells using GM easy^TM Lentiviral packaging system (Genomeditech, GMeasy-10), which was later used to transduce cells. 3 days post transduction, puromycin was added to the medium as a selection pressure for two rounds. The surviving cells were further analyzed for stable expression of huCD98hc or cynoCD98hc by flow cytometry.
6.10.3 Example 3: Generation of anti-CD98hc hybridoma antibodies

Balb/c and C57bl/6 mice were repeatedly immunized once every two weeks by subcutaneous or intraperitoneal injections of human CD98hc ECD domain with adjuvant. During the injection intervals, sera from the mice on day 21 and day 35 were parallelly analyzed by ELISA for titer against human, cyno CD98hc ECD and by FACS for reactivity to overexpressing human CD98hc HEK293 cells. Three days following the final boost, a single cell suspension of lymphocytes was obtained from spleen of animals with the highest titers. The cell fusion was performed via electrofusion with SP2/0 myeloma cells at a ratio of 1: 10. These cells were plated in 96-wells plates with a hypoxanthine-aminopterin-thymidine medium (HAT medium) to select hybridoma. After 10-12 days of culture, supernatant from hybridoma were collected for binders screening against huCD98hc overexpressed HEK293 cells, Cyno CD98hc CHOK1 cells and HEK293 parental cells. In total 875 clones from two rounds of fusions have been screened by FACS. 268 hits (cutoff: MFI ratio over Isotype >10 against huCD98hc HEK293 cell) were then tested in a DT3C killing assay as confirmatory functional test for antibody internalization (Table 14) .

DT3C is a protein composed of a diphtheria toxin (DT) lacking the receptor binding domain but containing the Fc binding domain of Streptococcus protein G (3C) . It can specifically bind to an antibody. When the antibody is internalized, DT3C can be cleaved by the cytosolic furin protease and release the cytotoxic catalytic domain into the cytoplasm (Toxins, 2020, 12: 658) . Thus, DT3C is mainly used for in vitro screening of internalization efficiency of antibodies. In brief, human CD98hc overexpressing HEK293 cells were seeded at a density of 5, 000 per well in 96-well cell culture plates for 24 hours culture prior to treatment. 2 μg/mL DT3C was pre-incubated with supernatants from hybridoma at 37℃ for 30 min to form the complex. Then the complex was added into the target cells followed a 48-hour incubation. The cell viability was assessed by luminescent cell viability assay (Promega, #G7571) .

Finally, 13 clones were selected and subjected to subcloning and V-region sequencing based on their binding affinity as well as endocytosis activity. Human IgG1 versions of recombinant antibodies in Table 14 were expressed and purified for further in vitro testing, including binding affinity by FACS, internalization activity by pHrodo labeling and Leucine uptake inhibition.

Table 14 Examples of hybridoma supernatant binding activity to huCD98hc and CynoCD98hc overexpressing cells

6.10.4 Example 4: Binding affinity of recombinant antibody to huCD98hc and
CynoCD98hc overexpressing cells

The binding of recombinant antibodies to cellular huCD98hc and CynoCD98hc were assessed by flow cytometry. Human CD98hc overexpressing HEK293 and Cyno CD98hc overexpressing CHO cell were utilized as positive cells, while CHOK1 cells were used as negative control. In general, single cell suspension was prepared with FACS buffer and then incubated with Magic^TM Fc Receptor blocker (Abace, CDN-ZF3) for 15 min. 100, 000 cells were seeded in cell culture plates and incubated with serially diluted antibodies starting from 10 μg/mL for 30 min. After washed three times, the cells were incubated with Alexa488 conjugated donkey anti-human IgG Fcγ fragment specific secondary antibody (Jackson, #709-545-098, 1: 200, 30 min, 4℃) . Binding activity was analyzed by flow cytometry (Millipore, Guava easyCyte BGV) .

As shown in FIGs. 1A-1C, all ten recombinant antibodies specifically bound to cellular human CD98hc (FIG. 1A) and eight antibodies were cross-reactive with cyno CD98hc (FIG. 1B) . None bound to wildtype CHO cells (FIG. 1C) .
6.10.5 Example 5: In vitro internalization of recombinant candidate antibody to
huCD98hc overexpressing HEK293

The internalization activity of candidate antibodies was evaluated in vitro by a pHrodo labeling based high-content imaging assay. In brief, huCD98hc overexpressing HEK293 cells were seeded at a density of 1.1x10⁴ cell per/well for 18 hours prior to treatment. Antibodies were pre-conjugated with an equal volume of pHrodo^TM iFL Green human IgG labeling reagent pHrodo-Green labeling reagent (Invitrogen, Zenon^TM , Z25611) at the molar ratio of 1: 4.5. Then the pHrodo-labelled antibodies were serially diluted into the cells followed by a 3-hour incubation. Finally, the plates were placed into high content analysis system (PerkinElmer, Operetta CLS) for images collection. An anti-CD98hc reference antibody (SIR-BP-R001, corresponding to CD98hc 4, Table 1 in WO2021205361A1) with reported internalization activity was applied as positive control.

As shown in FIG. 2, all ten candidate antibodies were effectively internalized.
6.10.6 Example 6: Recombinant antibody function assessment on Leucine uptake

The huCD98hc/LAT1 overexpressing HEK293 cell were seeded into 96-well plates (50, 000 cells/well) and incubated overnight at 37 ℃. On the next day, the cells were washed once with warm HBSS before treatment. Anti-CD98 antibodies or control LAT1 inhibitor JPH203 were added to cells for 5 min incubation, followed by 100 μM [¹³C6, ¹⁵N] -L-Leucine (Sigma-Aldrich, CAS: 202406-52-8) . Cells were incubated at 37 ℃ under gentle agitation for 20 min. After removing the [¹³C6, ¹⁵N] -L-Leucine solution, the plates were washed three times with ice-cold HBSS. Cells were then lysed with 0.6%n-Decyl-β-D-maltopyranoside (anatrace, D32225GM) in 50 mM tris HCL buffer with 150 mM NaCl and protease inhibitor cocktail (cOmplete^TM, Mini Protease Inhibitor Cocktail, Roche) . The cell homogenates were spiked with 0.5 μM L-Leucine-D3 as internal standard following with the process of protein precipitation by 0.1%formic acid in 90%acetonitrile. The plates were centrifuged for 10 min at 800xg prior to UPLC-MS/MS system analysis. Determination of [¹³C6, ¹⁵N] -L-Leucine as performed on a Vanquish High Performance Liquid Chromatogram (Thermo Fisher Scientific, US) and Q-Exactive mass spectrometer equipped with Heated Electrospray Ionization source. The parallel reaction monitoring (PRM) in the positive mode was applied for quantification analysis of [¹³C6, ¹⁵N] -L-Leucine and ³H-leucine as internal standard. The inhibition of [¹³C6, ¹⁵N] -L-Leucine relative to the isotype control [Mean+ (3xSD) ] reflected the antagonist activity.

As shown in FIG. 3, none of the candidate antibodies showed significant inhibition of leucine uptake. Only the reference antibody (SIR-BP-R001) , SIR-BP-H004, SIR-BP-H007, and SIR-BP-H008 showed marginal inhibitory effect at high concentration of 100 μg/mL (666.66 nM) .
6.10.7 Example 7: Generation of bsAb of IgG-scFv (2+1) format

An anti-CD98hc scFv was fused to the C-terminus of an anti-LILRB2 IgG heavy chain via a short (GGAGGA) (SEQ ID NO: 132) or long linker (GGGGS) 3 (SEQ ID NO: 130) to prepare the bsAb in IgG-scFv format (2+1) . The bsAb has three peptide chains, namely, the first heavy chain HC1, the second heavy chain HC2, and the light chain LC, with the first heavy chain containing the scFv at its C-terminus. The VH and VL domains within scFv were connected by a long linker GTEGKSSGSGSESKST (SEQ ID NO: 131) or (GGGGS) 3 (SEQ ID NO: 130) . In some instances, the scFvs were in a VL-linker-VH format. Mutations in CH3 (HC1: T350V, L351Y, F405A, Y407V; HC2: T350V, T366L, K392L, T394W) were incorporated in the antibody heavy chain to facilitate asymmetric heterodimerization. In some cases, a Knob (T366W) mutation and a hole mutation (T366S, L368A, Y407V) in the constant regions were used. To better remove the homodimeric side products in purification process, a RF mutation (H435R, Y436F) was incorporated into the CH3 domain of the heavy chain HC2. For some bispecific antibodies, additional Hisx6 tag was used in the C-terminus of HC2 for a two-step purification by Ni-NTA.

Exemplary IgG-scFv 2+1 format bispecific antibodies are shown in Table 15. The anti-LILRB2 antibody had the VH and VL of SEQ ID NOs: 120 and 121, respectively. HC1: the first heavy chain

Table 15 Examples of IgG-scFv 2+1 format bispecific antibodies

6.10.8 Example 8: Cell binding of the candidate bispecific antibodies and CD98hc
specificity

The binding of the candidate anti-CD98hc bispecific antibodies to cellular CD98hc was evaluated by FACS using huCD98hc overexpressing HEK293, CynoCD98hc overexpressing CHOK1 and CHOK1 parental cells, respectively. The sample treatment followed the procedure as described above in Example 4. FACS results showing the binding of the bispecific antibodies are shown in Table 16.

Table 16 Cellular binding of IgG-scFv 2+1 anti-CD98hc bispecific antibodies

6.10.9 Example 9: Internalization ability of candidate bispecific antibodies into
huCD98 expressing cell line

Exemplary bispecific anti-CD98hc antibodies described in Example 7 were tested for their internalization activity in a pHrodo labeling HCI assay similar to that described above in Example 5. An isotype hIgG1 antibody was included as a negative control and a reported anti-CD98hc bispecific antibody (SIR-BP-R005, LILRB2-CD98hc bispecific containing SIR-BP-R001 in scFv form) also served as a reference. As shown in FIG. 4, SIR-BP-JHS005, SIR-BP-JHS007, and SIR-BP-JHS009 all showed superior internalization activity than the reference antibody.
6.10.10 Example 10: In vivo PK of candidate bispecific antibodies in huCD98 knock-in
mice

Humanized mouse lines expressing human extracellular domains of CD98hc were generated by Biocytogen. In brief, CRISPR was used to replace the mouse ECD with the human version, while retaining the mouse transmembrane and intracellular regions under the control of mouse promotor (WO 2023/109956 A1) . In vivo expression level of the human ECD was evaluated by western blot. Immunostaining result of brain slice further confirmed the colocalization of human CD98 ECD with both CD31 and LAT1 in brain microvessel region (data not shown) . 3 bispecific antibodies were selected for an in vivo PK exploration in huCD98 KI mice based on the following considerations: (1) cross reactivity between human and cyno CD98hc; (2) covering a broad range of binding affinity and internalization activity; and (3) lack of high developability risk such as PTM in CDR regions. In brief, groups of huCD98hc KI mice were administered with 10mg/kg of test antibodies by single IV bolus at day 0. The monoclonal anti-LILRB2 hIgG1 antibody was utilized as the isotype control. Plasma was collected at scheduled timepoints to monitor the peripheral clearance of antibodies during in-life phase. After 24 hours, a cardiac perfusion with PBS was performed on the anesthetized mice to rinse out the vessel blood. Brain was collected and cut in half for weighting. Tissues were added to a calculated volume of 1%NP40 dPBS buffer (0.2g tissue/1.0 mL buffer) with 1x protease inhibitor (cOmplete^TM, Mini Protease Inhibitor Cocktail, Roche) . Brain samples were homogenized at 8500 rmp of 30 seconds for 3 times and then were kept on ice for 0.5 hour. After complete lysis, the samples were centrifuged at 5400xg for 15 mins and the supernatant were transferred into new tubes for total protein quantification by BCA analysis (Pierce BCA Protein Assay Kit, #23225) . Both plasma and brain samples were analyzed by a commercially available hIgG ELISA kit following its instructions (IgG Human kit, Abcam, #ab195215) . Briefly, plasma or brain samples were diluted in PBS+0.5%BSA with certain dilution factor (plasma 500-100, 000; brain: 15-20) . The standard samples were prepared with the concentration as follows: 15, 7.5, 3.75, 1.87, 0.93, 0.47, 0.23 and 0 ng/mL. Then the capture and detection antibodies were diluted and mixed with 50 μL samples or standard. The mixture was added to the precoated plates and gently rotated at room temperature for 40 mins. After final washing, the plates were developed by adding tetramethylbenzidine solution and incubated for 5-10 mins. The reaction was stopped by adding 100 μL stop solution. The OD value at 450 was recorded by a microplate reader (CLARIOstar^plus, BMG LABTECH) . The amount of hIgG in brain or plasma was determined by back-calculating with standard curve and dilution factor.

As shown in FIG. 5, all three anti-CD98hc bispecific antibodies showed a clear target mediated disposition in the periphery, which resulted in a faster plasma clearance than the isotype control. FIG. 6 shows the anti-CD98hc bispecific antibodies levels in brain homogenates. For all of three antibodies, there was a 2.7 to 5-fold increase in brain uptake compared to isotype control at 24 hours. In addition, brain/plasma ratio at terminal time point was significantly increased by 22 to 82-fold.
6.10.11 Example 11: Capillary depletion demonstrated the penetration of anti-CD98hc
binding molecules to brain parenchyma

Capillary depletion was performed on the brain samples following the protocol described below. The half brain was homogenized in cold HBSS containing protease inhibitors (cOmplete^TM, Mini Protease Inhibitor Cocktail, Roche) . Then the homogenates were centrifuged at 1, 000 g for 10 min. After washing with dPBS, cell pellets were resuspended in 10%dextran and the solution were centrifuged at 5, 400 g for 15 min. The supernatant was transferred to a new tube and washed with 10 mL HBSS buffer. Finally, the parenchyma cell pellets were lysed in 1%NP-40 PBS with protease inhibitors (cOmplete^TM, Mini Protease Inhibitor Cocktail, Roche) prior to human IgG ELISA assay described above. Total protein concentration of the parenchymal fraction was measured using BCA assay (Pierce BCA Protein Assay Kit, Thermo, #23225) .

Human IgG level was normalized to protein concentration. As shown in FIG. 7, a significantly elevated (5-8 fold compared with Isotype control) hIgG concentration in parenchymal fraction was observed at 24 hours after dosing, demonstrating that the bispecific antibodies could cross the BBB and penetrate into parenchymal regions through the CD98hc binding motif.
6.10.12 Example 12: Humanization of anti CD98hc scFv

Candidate anti-CD98 antibody SIR-BP-H005 and SIR-BP-H009 were chosen for humanization and further development. Complementarity-determining region (CDR) grafting technology was used, in which the antigen-binding specificity of a murine antibody was transferred to a human antibody by replacing the CDR loops and selected variable-region framework residues. The reshaped, humanized antibody only retained the essential binding elements from the murine antibody (5–10%of total sequence) and was predicted to be minimally immunogenic. The general progression of CDR grafting included structure modeling, framework selection, CDR grafting and back mutation. As a first step in CDR grafting, a structural model of the murine variable region was constructed using the antibody modeler module of MOE (Molecular Operating Environment, Chemical Computing Group, Montreal, Canada) . As the second step, VH and VL sequences of the murine mAb sequence to be humanized were compared to human VL, VH, LJ, HJ functional germline sequences taken from a database of 114 approved human antibodies out of 629 CSTs collected from OPIG (http: //opig. stats. ox. ac. uk/) . Pseudo-genes and ORFs were ignored. The VH and VL germline sequences that shared the highest sequence homology/identity with the murine frameworks were chosen as the human acceptor frameworks, especially at the critical framework positions. And the most similar VJ and HJ genes were combined. Having finalized the acceptor framework sequences, CDRs of murine anti-CD98 antibody were transplanted onto the human framework. Although antigen binding was predominantly regulated by CDR residues, framework residues might also contribute, either through direct antigen contact or indirectly through packing with CDR residues. The implication for CDR grafting is that it might be necessary to revert one or more human framework residues to the murine equivalents in the reshaped antibody (so-called framework back-mutations) to restore the native biomolecular environment for antigen binding. The BioMOE module of MOE was utilized to identify the canonical residues in the framework that were near the CDRs or the VL/VH interface, contain strong H-bond interactions with CDRs, charge is different from original residues or the foundation residues. The Protein Builder module of MOE was utilized to visualize and analyze the potential residues for back-mutation. Potential back-mutation residues were individually evaluated and the significantly disrupting mutations were reverted back to the original query residues. As a result, humanized sequences could contain up to six back mutations. The murine mAbs and the humanized mAbs are listed as scFv in Table 5c and Table 9c.
6.10.13 Example 13: Binding kinetics of anti-CD98hc bispecific antibodies

Binding kinetics of anti-CD98hc bispecific antibodies were evaluated by BLI on Octet Red384 system (Fortebio, Sartorius) . Briefly, AHC2 Biosensors were pre-equilibrated with running buffer for 10 minutes. Antibodies were diluted to 10 μg/mL and transferred to black 384-well MIRCOPlates (Greiner, #781209) with aliquots of 90 μL. Recombinant human and cynomolgus CD98hc ECD antigen described above in the Example 1 were diluted in system buffer (HBS-EP+, Cytiva, #BR100669) , to a concentration of 400 nM, then serially diluted to 200, 100, 50, 25, 12.5, 6.25 nM. Antibodies were immobilized on AHC2 biosensors by dipping the sensors into the wells for 300s with flowrate of 1000 rpm. In the association step, sensors were dipped into wells containing serially diluted antigen. The subsequent dissociation step was performed with the system buffer for 300s. Data was analyzed using Fortebio Data Analysis 11.1 software to generate kinetic constants. The K_on (on-rate) , K_dis (off-rate) and K_D (equilibrium dissociation constant) for each bispecific antibodies were reported Table 17. These bispecific antibodies exhibited a range of affinities from 9 nM to 108 nM for human CD98hc ECD. All the antibodies showed cross-reactivity with the 100-200 nM range of affinities for cynomolgus CD98hc ECD.

Table 17 Binding affinity of bispecific antibodies for human and cyno CD98hc ECD

6.10.14 Example 14: In vivo PK of humanized bispecific antibodies in huCD98 knock-in
mice

To characterize the brain uptake of humanized anti-CD98hc bispecific antibodies, 14-week-old homozygous CD98hc knock in mice were intravenously dosed 10 mg/kg. An antibody containing the same Fab sequence without anti-CD98hc scFv was utilized as control IgG. Plasma and brain were collected at 24 hours and 72 hours post dosing. Concentrations of hIgG were measured by the ELISA method described above.

As shown in FIG. 8, elevated hIgG concentrations were detected for the two bispecific antibodies in brain compared with isotype control. The fold change over control IgG was further increased to 5.33 and 7.8 fold, respectively, at 72 hours. Similarly, the humanized antibodies exhibited an on target mediated peripheral clearance as previously described. The brain/plasma ratio of the bispecific antibodies were significantly elevated by 18-40 fold at 24 hours and 144-270 fold at 72 hours as shown in FIG. 9.
6.10.15 Example 15: Non-human primates in vivo PK of LILRB2-CD98hc bispecific
antibody

To explore the PK profile of anti-CD98hc bispecific in non-human primates, a single dose of 10 mg per kilogram antibodies were administrated to male cynomolgus monkeys via intravenous infusion (Table 18) . Bispecific antibody SIR-BP-R009 was constructed that shared the same anti-LILRB2 warhead with SIR-BP-BHS005 but had a reported TfR binding motif (WO-2014189973 A2) . The anti-LILRB2 antibody was used as a control group.

Overall, the monkeys from all three groups were well tolerated during the treatment. No notable changes were observed in body weight, food consumption and clinical observation after administration.
Table 18 Cynomolgus monkey PK study design

The human IgG concentrations in monkey serum samples were quantified using a UPLC-high resolution Q Exactive mass spectrometer based bioanalysis method involving enzymatic digestion of target antibody. In brief, a protein precipitation procedure using 1%TCA in isopropanol (1: 3 volume ratio) was added into monkey serum to remove unwanted matrix protein. Pellets were resuspended by the addition of 75 μL 100mM Tris buffer (pH 8.0, containing 1 μg/mL internal standard) . The reconstitute solution was performed with a trypsin digestion at 37℃ for 2 hours. Three sets of calibration standards and QC samples were subjected to the same precipitation and digestion procedure. Finally, the digestion was stopped by acidification with 1%formic acid and centrifuged at 14000 rpm for 20 min prior to LC-MS/MS analysis. The parallel reaction monitoring (PRM) in the positive mode was applied for quantification analysis of fragment peptide GPSVFPLAPSSK (SEQ ID NO: 136) with its isotope labelled peptide as internal standard. At least six points calibration standards were fitted to a 1/x or 1/x² weighted linear regression model. The equation of curve was then used to calculate the predicted concentration in serum samples. Performance of standard curve was verified against QC samples at three concentration levels.

Results shown in FIG. 10 illustrate that both the anti-LILRB2/CD98hc and anti-LILRB2/TfR bsAbs showed increased serum clearance in non-human primates (NHPs) due to binding to target in peripheral tissues, comparing with non-binding control of anti-LILRB2. In the first 72 hours, anti-LILRB2/CD98hc bsAb showed similar serum clearance as compared to anti-LILRB2 control. Then an accelerated peripheral clearance was observed in anti-LILRB2/CD98hc bsAb treatment group from day 7, which was below LLOQ (1 μg/mL) of LC-MS/MS measurement.
6.10.16 Example 16: CSF penetration of LILRB2-CD98hc bispecific antibody in Non-
human primates

Cerebrospinal fluid (CSF) was collected from monkeys at various timepoints after a single dose described in Example 15. The detection of CSF samples utilized a Sandwich ELISA method described as below.

Briefly, 0.15 μg/well LILRB2 ECD protein was coated to a 96-well high binding plate at 4℃ overnight. Then the plate was blocked with 5%BSA in PBST (0.05%Tween-20 in 1xPBS) for 1 hour at room temperature. Test samples were diluted to the minimum required dilution in dPBS with cOmplete^TM, Mini Protease Inhibitor. Calibration standards and QCs were prepared in the same assay buffer with additional blank CSF as matrix (1: 6 volume ratio) . Standards and samples were incubated with agitation for 90 min at room temperature. Then the plate was washed 4 times with PBST. A mouse anti human IgG antibody (abcam, #ab124055) was 1: 4000 diluted in dilution buffer as detective antibody followed by 1 hour incubation at room temperature. The plate was then washed 5 times and added a HRP conjugated goat anti-mouse IgG H&L (1: 10000, abcam, #ab6789) for 1 hour incubation. After final wash, the plate was developed by adding TMB substrate and incubated for 5-10 minutes. Reaction was quenched by adding 100 μL stop solution and OD at 450nm was recorded by microplate reader. The concentration of hIgG in CSF samples were back calculated to the standard calibration curve as illustrated in FIG. 11.

Compared with anti-LILRB2/TfR and anti-LILRB2 alone, there was about 4-fold increased Cmax in CSF detected in the anti-LILRB2/CD98hc administration group at 2 hours. CSF AUC was about 2-fold over anti-LILRB2 alone and anti-LILRB2/TfR group. ^CSF AUC/^Serum AUC ratio for anti-LILRB2/CD98hc was about 8.4 fold over anti-LILRB2 alone and about 2.7 fold over anti-LILRB2/TfR respectively. As such, the anti-LILRB2/CD98hc demonstrated a superior NHP CSF PK than both anti-LILRB2 and anti-LILRB2/TfR in the first 10 days after administration.
***

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims.

Accordingly, the preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

Claims

An antibody or antigen-binding fragment thereof that specifically binds human CD98 heavy chain (CD98hc) , comprising

(a) a heavy chain variable region (VH) comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 25, 26 and 27, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a light chain variable region (VL) comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 28, 29, and 30, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 1, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 25, 26, 27, 28, 29, and 30, respectively.
The antibody or antigen-binding fragment of claim 1, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 5; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 6.
The antibody or antigen-binding fragment of claim 3 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 5 and 6, respectively.
The antibody or antigen-binding fragment of any one of claims 1 to 4 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 31, 32 and 33, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 34, 35, and 36, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 6, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 31, 32, 33, 34, 35, and 36, respectively.
The antibody or antigen-binding fragment of claim 6, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 7; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 8.
The antibody or antigen-binding fragment of claim 8 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 7 and 8, respectively.
The antibody or antigen-binding fragment of any one of claims 6 to 9 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 37, 38 and 39, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 40, 41, and 42, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 11, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 37, 38, 39, 40, 41, and 42, respectively.
The antibody or antigen-binding fragment of claim 11, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 9; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 10.
The antibody or antigen-binding fragment of claim 13 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 9 and 10, respectively.
The antibody or antigen-binding fragment of any one of claims 11 to 14 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 43, 44 and 45, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 46, 47, and 48, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 16, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 43, 44, 45, 46, 47, and 48, respectively.
The antibody or antigen-binding fragment of claim 16, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 11; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 12.
The antibody or antigen-binding fragment of claim 18 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 11 and 12, respectively.
The antibody or antigen-binding fragment of any one of claims 16 to 19 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 49, 50 and 51, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 52, 53, and 54, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 21, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 49, 50, 51, 52, 53, and 54, respectively.
The antibody or antigen-binding fragment of claim 21, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 49, 118, 51, 52, 53, and 54, respectively.
The antibody or antigen-binding fragment of claim 21, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 13 and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 14.
The antibody or antigen-binding fragment of claim 24 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 13 and 14, respectively.
The antibody or antigen-binding fragment of any one of claims 21 to 25 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of claim 26 that is a humanized antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of claim 27, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 102, 104, 106, 108, 110, and 137; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 103 or 105.
The antibody or antigen-binding fragment of claim 28 comprising a VL and a VH having the amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; or (6) SEQ ID NOs: 137 and 103, respectively.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 55, 56 and 57, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 58, 59, and 60, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 30, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 55, 56, 57, 58, 59, and 60, respectively.
The antibody or antigen-binding fragment of claim 30, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 15; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 16.
The antibody or antigen-binding fragment of claim 32 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 15 and 16, respectively.
The antibody or antigen-binding fragment of any one of claim 30 to 33 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 61, 62 and 63, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 64, 65, and 66, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 35, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 61, 62, 63, 64, 65, and 66, respectively.
The antibody or antigen-binding fragment of claim 35, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 17; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 18.
The antibody or antigen-binding fragment of claim 37 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 17 and 18, respectively.
The antibody or antigen-binding fragment of any one of claims 35 to 38 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 67, 68 and 69, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 70, 71, and 72, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 40, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 67, 68, 69, 70, 71, and 72, respectively.
The antibody or antigen-binding fragment of claim 40, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 19; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 20.
The antibody or antigen-binding fragment of claim 42 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 19 and 20, respectively.
The antibody or antigen-binding fragment of any one of claims 40 to 43 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 73, 74 and 75, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 76, 77, and 78, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 45, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 73, 74, 75, 76, 77, and 78, respectively, or SEQ ID NOs: 73, 74, 119, 76, 77, and 78, respectively.
The antibody or antigen-binding fragment of claim 45, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 21; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 22.
The antibody or antigen-binding fragment of claim 47 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 21 and 22, respectively.
The antibody or antigen-binding fragment of any one of claims 45 to 48 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of claim 49 that is a humanized antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of claim 50, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 112, 114, and 116; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to SEQ ID NO: 113.
The antibody or antigen-binding fragment of claim 51 comprising a VL and a VH having the amino acid sequences of (1) SEQ ID NOs: 112 and 113, respectively; (2) SEQ ID NOs: 114 and 113, respectively; or (3) SEQ ID NOs: 116 and 113, respectively.
An antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising

(a) a VH comprising VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 79, 80 and 81, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VH CDRs and

(b) a VL comprising VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 82, 83, and 84, respectively; or a variant thereof having up to about 5 amino acid substitutions, additions, and/or deletions in the VL CDRs.
The antibody or antigen-binding fragment of claim 53, comprising VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3, having the amino acid sequences of SEQ ID NOs: 79, 80, 81, 82, 83, and 84, respectively.
The antibody or antigen-binding fragment of claim 53, comprising:

(a) a VH having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 23; and/or

(b) a VL having at least 85%, at least 90%, at least 95%, at least 98%, or 100%sequence identity to the amino acid sequence of SEQ ID NO: 24.
The antibody or antigen-binding fragment of claim 55 wherein the VH and the VL have the amino acid sequences of SEQ ID NOs: 23 and 24, respectively.
The antibody or antigen-binding fragment of any one of claims 53 to 56 that is a chimeric antibody or antigen-binding fragment, a humanized antibody or antigen-binding fragment, or a human antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of any one of claims 1 to 57 that is selected from the group consisting of a Fab, a Fab’, a F (ab’) ₂, a Fv, a scFv, a (scFv) ₂, a single domain antibody (sdAb) , and a heavy chain antibody (HCAb) .
The antibody or antigen-binding fragment of claim 58 that is an scFv.
The antibody or antigen-binding fragment of claim 59, wherein the scFv comprises from N terminus to C terminus, the VH, a linker, and the VL.
The antibody or antigen-binding fragment of claim 59, wherein the scFv comprises from N terminus to C terminus, the VL, a linker, and the VH.
The antibody or antigen-binding fragment of claim 60 or 61, wherein the linker has an amino acid sequence selected from the group consisting of SEQ ID NOs: 130-132.
The antibody or antigen-binding fragment of any one of claims 1 to 57 that is an IgG1 antibody, an IgG2 antibody, an IgG3 antibody, or an IgG4 antibody.
An antibody or antigen-binding fragment thereof that competes with the antibody or antigen-binding fragment of any one of claims 1 to 63 for binding to human CD98hc.
The antibody or antigen-binding fragment of any one of claims 1 to 64 that is a bispecific antibody or a multispecific antibody.
The antibody or antigen-binding fragment of any one of claims 1 to 65 that is a monoclonal antibody or antigen-binding fragment.
The antibody or antigen-binding fragment of any one of claims 1 to 66, wherein the antibody or antigen binding fragment is an internalizing antibody or antigen binding fragment.
The antibody or antigen-binding fragment of any one of claims 1 to 67, wherein the antibody or antigen binding fragment can cross the blood brain barrier (BBB) .
The antibody or antigen-binding fragment of any one of claims 1 to 68, wherein the antibody or antigen binding fragment does not inhibit leucine uptake.
A polynucleotide encoding a polypeptide of the antibody or antigen-binding fragment of any one of claims 1 to 69.
A vector comprising the polynucleotide of claim 70.
A host cell comprising the polynucleotide of claim 70, or the vector of claim 71.
A method of making an antibody or antigen-binding fragment thereof that specifically binds human CD98hc, comprising culturing the cell of claim 72 under conditions that allow expression of the antibody or antibody fragment.
The method of claim 73 that comprises isolating the antibody from the culture.
A conjugate comprising the antibody or antigen-binding fragment of any one of claims 1 to 69 linked to an effector moiety.
The conjugate of claim 75, wherein the effector moiety is selected from the group consisting of drugs for neurological diseases or disorders, neurotrophic factors, growth factors, enzymes, cytotoxic agents and imaging agents.
A method of delivering an effector moiety across BBB in a subject comprising administering to a subject a conjugate comprising the antibody or antigen-binding fragment of any one of claims 1 to 69 linked to the effector moiety.
A fusion protein comprising the antibody or antigen-binding fragment of any one of claims 1 to 69 linked to a second antibody or antigen-binding fragment that specifically binds to a central nervous system (CNS) antigen.
The fusion protein of claim 78, wherein the CNS antigen is selected from the group consisting of alpha-synuclein, amyloid precursor protein (APP) , amyloid-beta (Aβ) , apolipoprotein E (ApoE) , apolipoprotein E4 (ApoE4) , ATP-binding cassette sub-family A member 1 (ABCA1) , ATP-binding cassette sub-family A member 7 (ABCA7) , beta-secretase 1 (BACE1) , caspase 6, CD20, CD33 (Siglec3) , death receptor 6 (DR6) , disialoganglioside (GD2) , epidermal growth factor (EGF) , epidermal growth factor receptor (EGFR) , epidermal growth factor receptor 2 (EGFR2/HER2) , gamma secretase, glycoprotein nonmetastatic melanoma protein B (GPNMB) , HLA-DR1, HLA-DR5, huntingtin, IL-34, IL1RAP, interleukin-13 receptor alpha 2 (IL-13Rα2) , leucine-rich repeat kinase 2 (LRRK2) , LILRB2, matrix metalloproteinases (MMPs) , membrane spanning 4-domains A4A (MS4A4A) , membrane spanning 4-domains A4E (MS4A4E) , membrane spanning 4-domains A 6A (MS4A6A) , p-glucocerebrosidase (GCase or GBA) , p75 neurotrophin receptor (p75NTR) , parkin, paired immunoglobin like type 2 receptor alpha (PILRA) , phosphorylated Tau, prion protein (PrP) , presenilin 1, presenilin 2, progranulin (PGRN) , prosaposin (PSAP) , sialic acid binding Ig-like lectin 11 (Siglec11) , sialic acid binding Ig-like lectin 5 (Siglec5) , sialic acid binding Ig-like lectin 7 (Siglec7) , sialic acid binding Ig-like lectin 9 (Siglec9) , sortilin (SORT) , sphingolipids, Tau protein, transmembrane protein 106B (TMEM106b) , triggering receptor expressed on myeloid cells 2 (TREM2) , TXNRD1, and ubiquitin protein ligase E3A (UBE3A) .
The fusion protein of claim 78 or 79, that is a bispecific antibody.
The fusion protein of claim 80 wherein the bispecific antibody comprises an IgG that specifically binds to the CNS antigen and an scFv that specifically binds to CD98hc.
The fusion protein of claim 81, wherein the scFv is linked to the C terminus of a heavy chain of the IgG.
The fusion protein of any one of claims 80 to 82, wherein the CNS antigen is LILRB2.
The fusion protein of claim 83, wherein the antibody that specifically binds to LIBRB2 comprises a VH having VH CDR1, VH CDR2, and VH CDR3 having the amino acid sequences of SEQ ID NOs: 122, 123 and 124, respectively, and a VL having VL CDR1, VL CDR2, and VL CDR3 having the amino acid sequences of SEQ ID NOs: 125, 126, and 127 respectively.
The fusion protein of claim 83, wherein the antibody that specifically binds to LIBRB2 comprises a VH and a VL having the amino acid sequences of SEQ ID NOs: 120 and 121, respectively.
A pharmaceutical composition comprising a therapeutically effective amount of the fusion protein of any one of claims 78 to 85, and a pharmaceutically acceptable carrier.
A method of treating a neurological disease or disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the fusion protein of any one of claims 78 to 85.
The method of claim 87, wherein the neurological disease or disorder is a neurodegenerative disease.
The method of claim 87 or 88, further comprising administering an additional therapy to the subject.
The method of any one of claims 87 to 89, wherein the subject is a human.
Use of fusion protein of any one of claims 78 to 85 for treating a neurological disease or disorder.
Use of fusion protein of any one of claims 78 to 85 for manufacture of a medicament for a neurological disease or disorder.
Use of claim 91 or 92, wherein the neurological disease is a neurodegenerative disease.
A bispecific antibody for CD98hc and LILBR2, comprising

(1) a first peptide chain (HC1) comprising, from N-terminus to C-terminus, VH1 and a first CH region, and a scFv;

(2) a second peptide chain (HC2) comprising, from N-terminus to C-terminus, VH1 and a second CH region; and

(3) a third peptide chain (LC) comprising, from N-terminus to C-terminus, VL1 and a CL region; wherein

(i) the VH1 and VL1 have the amino acid sequences of SEQ ID NOs: 120 and 121, respectively; and

(ii) the scFv comprises VH2 and VL2 having the amino acid sequences of (1) SEQ ID NOs: 5 and 6, respectively; (2) SEQ ID NOs: 7 and 8, respectively; (3) SEQ ID NOs: 9 and 10, respectively; (4) SEQ ID NOs: 11 and 12, respectively; (5) SEQ ID NOs: 13 and 14, respectively; (6) SEQ ID NOs: 15 and 16, respectively; (7) SEQ ID NOs: 17 and 18, respectively; (8) SEQ ID NOs: 19 and 20, respectively; (9) SEQ ID NOs: 21 and 22, respectively; or (10) SEQ ID NOs: 23 and 24, respectively; or humanized versions thereof.
The bispecific antibody of claim 94, wherein the VH2 and VL2 have amino acid sequences of (1) SEQ ID NOs: 102 and 103, respectively; (2) SEQ ID NOs: 104 and 105, respectively; (3) SEQ ID NOs: 106 and 103, respectively; (4) SEQ ID NOs: 108 and 103, respectively; (5) SEQ ID NOs: 110 and 103, respectively; (6) SEQ ID NOs: 137 and 103, respectively; (7) SEQ ID NOs: 112 and 113, respectively; (8) SEQ ID NOs: 114 and 113, respectively; or (9) SEQ ID NOs: 116 and 113, respectively.
The bispecific antibody of claim 94, wherein the scFv has at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 92-101 and 138.
The bispecific antibody of any one of claims 94 to 96, wherein the CL region is Cκ.
The bispecific antibody of any one of claims 94 to 97, wherein the first CH region further has T350V, L351Y, F405A, and Y407V substitutions and the second CH region has T350V, T366L, K392L, and T394W substitutions.
The bispecific antibody of any one of claims 94 to 97, wherein the first CH region further has T366W substitution, and the second CH region further has T366S, L368A, and Y407V substitutions.
The bispecific antibody of claim 98 or 99, wherein the first and second CH regions further have L234A, L235A, and D266S substitutions (AAS mutations) , or M252Y, S254T, and T256E (YTE mutations) , or both AAS mutations and YTE mutations.
The bispecific antibody of claim 98 or 99, wherein the second CH region further has H435R and Y436F substitutions.
The bispecific antibody of claim 94, wherein the HC1, HC2, and LC are at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%identical to amino acid sequences of (1) SEQ ID NOs: 85, 86, and 87, respectively; (2) SEQ ID NOs: 88, 86, and 87, respectively; (3) SEQ ID NOs: 89, 86, and 87, respectively; (4) SEQ ID NOs: 90, 86, and 87, respectively; or (5) SEQ ID NOs: 91, 86, and 87, respectively.
A polynucleotide or a plurality of polynucleotide that encodes or collectively encode the three peptide chains of the bispecific antibody of any one of claims 94 to 102.
A host cell comprising the polynucleotide or plurality of nucleotide of claim 103.
A method of making a bispecific antibody that specifically binds human CD98hc, comprising culturing the cell of claim 104 under conditions that allow expression of the bispecific antibody.
The method of claim 105 that comprises isolating the antibody from the culture.
A pharmaceutical composition comprising a therapeutically effective amount of the bispecific antibody of any one of claims 94 to 102, and a pharmaceutically acceptable carrier.
A method of treating a neurological disease or disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the bispecific antibody of any one of claims 94 to 102.
The method of claim 108, wherein the neurological disease or disorder is a neurodegenerative disease.
The method of claim 108 or 109, further comprising administering an additional therapy to the subject.
The method of any one of claims 108 to 110, wherein the subject is a human.
Use of conjugate of any one of claims 94 to 102 for treating a neurological disease or disorder.
Use of conjugate of any one of claims 94 to 102 for manufacture of a medicament for a neurological disease or disorder.
Use of claim 112 or 113, wherein the neurological disease or disorder is a neurodegenerative disease.