WO2025194075A1

WO2025194075A1 - Pharmaceutically acceptable salts of cysteamine-pantetheine disulfide and uses thereof

Info

Publication number: WO2025194075A1
Application number: PCT/US2025/019991
Authority: WO
Inventors: Kathlene Powell; Patrice P. RIOUX; Xiaoyang Wang; Meiqi LI; Xiaoyu Ma
Original assignee: Thiogenesis Therapeutics Inc
Current assignee: Thiogenesis Therapeutics Inc
Priority date: 2024-03-14
Filing date: 2025-03-14
Publication date: 2025-09-18
Anticipated expiration: 2026-09-14

Abstract

The present invention composition features pharmaceutically acceptable salts of cysteamine-pantetheine disulfide and compositions thereof. The pharmaceutically acceptable salts of cysteamine-pantetheine disulfide may be used to treat a disease or condition, such as a neurological injury, an inflammatory condition, chronic pain, or a psychological condition, in a subject in need thereof.

Description

PHARMACEUTICALLY ACCEPTABLE SALTS OF CYSTEAMINE-PANTETHEINE DISULFIDE AND USES THEREOF

FIELD OF THE INVENTION

The invention features compositions and methods for treating cysteamine-sensitive disorders.

BACKGROUND

Significant interest in the therapeutic application of cysteamine-pantetheine disulfide has developed, based upon evidence of possible therapeutic effects in a wide array of clinical applications that aim to treat cysteamine-sensitive disorders. Cysteamine-sensitive disorders are disorders or diseases for which there is preclinical or clinical evidence for cysteamine therapeutic benefit, including neurodegenerative diseases, including Alzheimer’s disease, Huntington’s disease and Parkinson’s disease; inflammatory and fibrotic diseases of the kidney, liver and lung; metabolic diseases including diabetes, metabolic syndrome and the spectrum of fatty liver diseases; infectious diseases, including viral, bacterial and parasitic infections; hypercholesterolemia; ischemic disease including ischemic heart disease or stroke; sickle cell anemia; inherited mitochondrial disorders; hereditary diseases caused by mutation of arginine to cysteine; and cancer.

Unfortunately, there is a class effect associated with all thiols (cysteamine, N-acetylcysteine, bucillamine, tiopronin, amifostine, etc.) which can induce adverse effects like nausea, vomiting, headache, muscle weakness at high dose. Cysteamine has very unpleasant sensory properties (foul odor and bitter taste) and can produce body odor and halitosis when ingested in therapeutically effective amounts (over one gram per day in adolescents and adults). Most patients also experience gastrointestinal side effects including anorexia, nausea, vomiting, and/or stomach pain. Halitosis, body odor, and gastrointestinal side effects have all been associated with high peak cysteamine blood levels (frequently over 50-fold higher than endogenous cysteamine levels in healthy subjects). Furthermore, the elimination half-life of cysteamine after oral administration is only about 25 minutes, which necessitates frequent dosing.

Cysteamine-pantetheine disulfide is a cysteamine precursor which converts to cysteamine in vivo. Neither cysteamine-pantetheine nor pantetheine, after reduction of the disulfide, is absorbed. Pantetheine is further enzymatically (vanin-1 ) converted into cysteamine in the Gl tract, and therefore two molecules of cysteamine for each molecule of cysteamine-pantetheine are absorbed across the entire length of the gastrointestinal tract, including the colon. After administration of cysteamine-pantetheine disulfide, cysteamine exhibits a favorable pharmacokinetic (PK) profile, and solves many of the problems with cysteamine administration, including halitosis, body odor, and gastrointestinal side effects, as well as a need for frequent dosing.

However, due to the physical properties of cysteamine-pantetheine disulfide free base form in the solid state, e.g., amorphous, difficult to isolate in high chemical purity, and poor chemical stability, there exists a need for cysteamine-pantetheine disulfide salts and formulations with improved characteristics. SUMMARY OF THE INVENTION

The invention features a pharmaceutically acceptable salt of cysteamine-pantetheine disulfide, wherein the pharmaceutically acceptable salt is a 2:1 malate salt.

In some embodiments, the pharmaceutically acceptable salt is stable for at least 1 month (e.g., at least 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, or 18 months, or more) when stored at 2-8 °C. In some embodiments, the pharmaceutically acceptable salt is stable for at least 1 week (e.g., at least 1 , 2, 3, or 4 weeks, at least 1 , 2, 3, 4, 5, or 6 months, or more) when stored at 25 °C and at 60% RH. In some embodiments, the pharmaceutically acceptable salt is stable for at least 3 months (e.g., at least 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 18, 24, 30, 36, 42, 48, or 60 months, or more) when stored at -20 °C.

In some aspects, the invention features a pharmaceutical composition comprising a cysteaminepantetheine disulfide 2:1 malate salt and a pharmaceutically acceptable excipient.

In some embodiments, the pharmaceutical composition is formulated in unit dosage form.

In some embodiments, the unit dosage form comprises In some embodiments, the unit dosage form comprises about 100 mg, about 200 mg, about 250 mg, about 500 mg, about 750 mg, about 1 ,000 mg, about 1 ,500 mg, about 2,000 mg, about 2,500 mg, about 3,000 mg, about 4,000 mg, about 5,000 mg, about 5,500 mg, about 6,000 mg, about 6,500 mg, about 7,000 mg, about 7,500 mg, about 8,000 mg, or about 8,500 mg of the cysteamine-pantetheine disulfide 2:1 malate salt. In some embodiments, the unit dosage form comprises about 4,100 mg of the cysteamine-pantetheine disulfide 2:1 malate salt. In some embodiments, the unit dosage form comprises about 8,200 mg of the cysteamine-pantetheine disulfide 2:1 malate salt.

In some embodiments, the pharmaceutical composition is formulated as a powder, a sachet, microcapsules, a liquid, or a suspension.

In some embodiments, the pharmaceutical composition is formulated for oral administration.

In some aspects, the invention features a method of treating a cysteamine-sensitive disorder a subject in need thereof, the method comprising administering to the subject a pharmaceutical composition described herein in an amount sufficient to treat the cysteamine-sensitive disorder.

In some embodiments, the cysteamine-sensitive disorder is cystinosis; neurodegenerative disease; neurodevelopmental disease; neuropsychiatric disease; mitochondrial disease; fibrotic diseases of the kidney, of the liver, or of the lung; parasitic disease; sickle cell disease; cancer; ischemic disease including stroke; chronic obstructive pulmonary disease (COPD); cystic fibrosis (CF); bacterial infection; viral infection; non-alcoholic steatohepatitis (NASH); alcoholic steatohepatitis; or non-alcoholic fatty liver disease (NAFLD). In some embodiments, the cysteamine-sensitive disorder is NASH. In some embodiments, the cysteamine-sensitive disorder is a neurodegenerative disease selected from Huntington's disease, neurodegenerative disorders with brain iron accumulation, Parkinson's disease, and Alzheimer's disease. In some embodiments, the cysteamine-sensitive disorder is a neurodevelopmental disorder selected from Rett syndrome and other disorders associated with MECP2 mutation. In some embodiments, the neurodevelopmental disorder is Rett syndrome. In some embodiments, the cysteamine-sensitive disorder is a mitochondrial disease selected from Leigh syndrome, MELAS, MERFF, and Friedreich's ataxia. In some embodiments, the mitochondrial disease is MELAS. In some embodiments, the cysteamine-sensitive disorder is a fibrotic disease selected from Alport's disease, focal segmental glomerulosclerosis (FSGS), alcoholic steatohepatitis (ASH), and pulmonary fibrosis. In some embodiments, the cysteamine-sensitive disorder is a bacterial infection or viral infection.

In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is from about 50 to about 150 milligrams per kilogram of body weight (mg/kg) (e.g., 60±10, 70±10, 80±10, 90±10, 100±25, 110±20, 120±10, 130±10, or 140±10 mg/kg) of a cysteamine-pantetheine disulfide salt form (e.g., a cysteamine-pantetheine disulfide malate (2:1 ) salt or a cysteamine-pantetheine disulfide succinate (2:1 ) salt) per day. In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is from about 3,000 mg to about 8,500 mg (e.g., about 3,000 mg, about 3,500 mg, about 4,000 mg, about 4,500 mg, about 5,500 mg, about 6,000 mg, about 6,500 mg, about 7,000 mg, about 7,500 mg, about 8,000 mg, or about 8,500 mg) of a cysteamine-pantetheine disulfide salt form (e.g., a cysteamine- pantetheine disulfide malate (2:1 ) salt or a cysteamine-pantetheine disulfide succinate (2:1 ) salt) per day. In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is from about 4,100 mg of a cysteamine-pantetheine disulfide malate (2:1 ) salt per day. In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is from about 8,200 mg of a cysteamine- pantetheine disulfide malate (2:1 ) salt per day. In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is about 5,500 mg of cysteamine-pantetheine disulfide malate (2:1 ) salt per day. In some embodiments, the pharmaceutical composition is administered orally. In some embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is from 2.5 g to 8.5 g per day (e.g., 3.0 ± 0.5 g, 3.5 ± 0.5 g, 4.0 ± 0.5 g, 4.5 ± 0.5 g, 5.0 ± 0.5 g, 5.5 ± 0.5 g, 6.0 ± 0.5 g, 6.5 ± 0.5 g, 7.0 ± 0.5 g per day, 7.5 ± 0.5 g per day, 8.0 ± 0.5 g per day, or 8.5 ± 0.5 g per day). In particular embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is about 5.5 g per day. In other particular embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is about 4.1 g per day. In other particular embodiments, the amount sufficient to treat the cysteamine-sensitive disorder is about 8.2 g per day.

Definitions

To facilitate the understanding of this invention, a number of terms are defined below and throughout the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology herein is used to describe specific embodiments of the invention, but their usage does not limit the invention, except as outlined in the claims.

Terms such as "a", "an," and "the" are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration.

As used herein, the term “about” refers to a value that is within 10% above or below the value being described.

The term “administration” or “administering” refers to a method of giving a dosage of a compound or pharmaceutical composition to a subject.

By “cysteamine content” is meant the fraction, by weight, of a cysteamine precursor convertible to cysteamine in vivo upon chemical and/or enzymatic degradation. As used herein, the terms “cysteamine-pantetheine disulfide” and “TTI-0102” refer to the compound having the following structure:

Cysteamine-pantetheine disulfide has a formula weight of 353.52 grams. In some embodiments, each molecule of cysteamine-pantetheine disulfide comprises two molecules of cysteamine content. One molecule of TTI-0102, upon disulfide bond reduction, yields one molecule of cysteamine and one molecule of pantetheine. Subsequent cleavage of pantetheine by intestinal pantetheinase yields one cysteamine and one pantothenic acid. Thus, one molecule of TTI-0102 yields two molecules of cysteamine.

By “cysteamine precursor” is meant a compound that can be converted under physiological conditions into at least one cysteamine. The means of conversion include reduction in the case of cysteamine containing disulfides (i.e., cysteamine mixed disulfides, i.e. , cysteamine-pantetheine disulfide), enzymatic hydrolysis in the case of pantetheinase substrates (i.e., pantetheine). In particular embodiments, the cysteamine precursor is cysteamine-pantetheine disulfide.

As used herein “cysteamine-sensitive disorder” means a disease for which there is evidence that cysteamine can be an effective treatment. The evidence may be derived from either clinical or preclinical studies of disease in mammals (e.g., humans, dogs, mice, rats, monkeys, rabbits), or from in vitro studies of disease mechanisms. Cysteamine-sensitive disorders constitute a broad, heterogeneous group of diseases with widely varying manifestations and pathogenesis. Diseases and disorders for which there is evidence of cysteamine efficacy may be classified according to pathogenesis, with the important caveat that the mechanism of cysteamine efficacy is not always clear and there may be unknown mechanisms of action. Important categories of cysteamine-sensitive disorders include (i) disorders of cystine transport, among which cystinosis is the best known; (ii) disorders associated with oxidative damage, including neurodegenerative and liver diseases; (iii) disorders associated with pathological enzyme activity, including neurodegenerative diseases, hereditary mitochondrial diseases, diseases associated with mutant MECP2 and POLG; (iv) fibrotic disorders, including fibrosis of the kidney, liver or lung; (v) metabolic disorders, including metabolic syndrome X, diabetes and the spectrum of non-alcoholic fatty liver disease, culminating in non-alcoholic steatohepatitis (NASH); (vi) infectious diseases, including certain viral infections (e.g., influenza), bacterial infections (e.g. Pseudomonas aeruginosa) and parasite infections (e.g. malaria; (vii) ischemic diseases, including ischemic-reperfusion injury of the heart and other organs; (viii) diseases associated with abnormal adiponectin metabolism; and (ix) cancer as well as amelioration of the deleterious effects of cancer therapy.

Several disease acronyms, gene names and other medical terms are represented by abbreviations. Disease acronyms include MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes) and MERFF (Myoclonic Epilepsy with Ragged Red Fibers). Gene names include POLG, which encodes the catalytic subunit of DNA polymerase gamma, a mitochondrial DNA polymerase; OCT1 , OCT2 and OCT3, which code for organic cation transporters 1 , 2 and 3 (also known as SLC22A1 , SLC22A2 and SLC22A3, respectively); PANK2, which encodes pantothenate kinase 2; VNN1 which encodes vanin 1 , also known as pantetheinase; VNN2 which encodes vanin 2, also known as GPI-80 and also a pantetheinase.

As used herein “pantetheine” refers to the D enantiomer (also occasionally referred to as the R enantiomer using more recent nomenclature). Pantetheine contains a chiral carbon in the pantothenoyl moiety which can exist in either the D (dextro) or L (levo) form, also referred to as the (R) or (S) forms, respectively. Only the D-pantetheine enantiomer is a substrate for pantetheinase, and it therefore is the only pantetheine enantiomer that is a cysteamine precursor.

The term “microparticles”, as used herein, refers to microbeads, microspheres, micropellets, nanoparticles, nanobeads, nanospheres or other fine particles used in drug formulations wherein each microparticle is between 0.05 - 999 micrometers in average diameter. Tens, hundreds or thousands of such microparticles may be used in a single unit dosage form, for example they may be packed inside a capsule or formulated as a powder or suspended in a liquid.

As used herein, a “pharmaceutically acceptable excipient” is a natural or synthetic substance included (together with the active ingredient) in the formulation of a composition that is suitable for use in humans and/or non-human mammals without undue adverse side effects (such as toxicity, irritation or allergic response). Excipients may include, for example: anti-adherents, antioxidants, binders, coatings, compression aids, disintegrants, dyes (colors), emollients, emulsifiers, fillers (diluents), film formers or coatings, flavors, fragrances, glidants (flow enhancers), lubricants, preservatives (including antioxidants), printing inks, sorbents, suspending or dispersing agents, solvents, colloid stabilizers, sweeteners, and water. The US FDA maintains a database of “inactive ingredients” which contains information on thousands of substances commonly used in formulating drugs. The database can be searched for excipients commonly used in controlled, delayed, sustained or extended release formulations. Excipients include, but are not limited to: butylated hydroxytoluene (BHT), calcium carbonate, calcium phosphate (dibasic), calcium stearate, carbomer, croscarmellose, crosslinked polyvinyl pyrrolidone, citric acid, crospovidone, cellulose derivatives including ethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose or hypromellose, docusate sodium, gelatin, gelucire 43/01 , lactose, magnesium stearate, maltitol, mannitol, methylcellulose, methyl paraben, microcrystalline cellulose, polyethylene glycol, polyethylene oxide), polyvinyl pyrrolidone, povidone, pregelatinized starch, propyl paraben, shellac, silicon dioxide, sodium carboxymethyl cellulose, sodium starch glycolate, sorbitol, starch (corn), stearic acid, sucrose, talc, titanium dioxide, vegetable oils, wax, including white, yellow or bees wax, and xylitol. Excipients may also include diluents (e.g., saline and aqueous buffer solutions), aqueous carriers, and nonaqueous carriers, for example, 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.

As used herein, the terms "pharmacologically effective amount," "therapeutically effective amount," and the like, when used in reference to a therapeutic composition, refer to a quantity sufficient to, when administered to the subject, including a mammal, for example a human, effect beneficial or desired results, such as clinical results. For example, in the context of treating depression, described herein, these terms refer to an amount of the composition sufficient to achieve a treatment response as compared to the response obtained without administration of the composition. The quantity of a given composition described herein that will correspond to such an amount may vary depending upon various factors, such as the given agent, the pharmaceutical formulation, the route of administration, the type of disease or disorder, the identity of the subject (e.g., age, sex, weight) or host being treated, and the like. An “effective amount,” "pharmacologically effective amount," or the like, of a composition of the present disclosure, also include an amount that results in a beneficial or desired result in a subject as compared to a control.

As used herein, the terms “treat,” “treating,” or “treatment” refer to administration of a compound or pharmaceutical composition for a therapeutic purpose. To “treat a disorder” or use for “therapeutic treatment” refers to administering treatment to a patient already suffering from a disease to ameliorate the disease or one or more symptoms thereof to improve the patient’s condition (e.g., by reducing one or more symptoms of inflammation). The term “therapeutic” includes the effect of mitigating deleterious clinical effects of certain inflammatory processes (i.e., consequences of the inflammation, rather than the symptoms of inflammation). The methods of the invention can be used as a primary prevention measure, i.e., to prevent a condition or to reduce the risk of developing a condition. Prevention refers to prophylactic treatment of a patient who may not have fully developed a condition or disorder, but who is susceptible to, or otherwise at risk of, the condition. Thus, in the claims and embodiments, the methods of the invention can be used either for therapeutic or prophylactic purposes.

The term “unit dosage form” refers to physically discrete units suitable as unitary dosages, such as a pill, tablet, caplet, hard capsule or soft capsule, each unit containing a predetermined quantity of a cysteamine precursor, or a pharmaceutically acceptable salt thereof. By “hard capsule” is meant a capsule that includes a membrane that forms a two-part, capsule-shaped, container capable of carrying a solid or liquid payload of drug and excipients. By “soft capsule” is meant a capsule molded into a single container carrying a liquid or semisolid or solid payload of drug and excipients. Granules, powders, microcapsules, and liquids can also be provided in “unit dosage form” by using appropriate packaging. For example, granules or powders can be administered in a sachet and liquids in an ampoule, vial, or plastic container.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

FIG. 1A and FIG. 1B are XRPD patterns of cysteamine-pantetheine disulfide succinate (2:1 ) salt (FIG. 1A) and cysteamine-pantetheine disulfide malate (2:1 ) salt (FIG. 1B).

FIG. 2A and FIG. 2B are DVS plots showing water desorption of cysteamine-pantetheine disulfide succinate (2:1 ) salt (FIG. 2A) and cysteamine-pantetheine disulfide malate (2:1 ) salt (FIG. 2B).

FIG. 3A and FIG. 3B are XRPD patterns of cysteamine-pantetheine disulfide succinate (2:1 ) salt (FIG. 3A) and cysteamine-pantetheine disulfide malate (2:1 ) salt (FIG. 3B) after water desorption.

FIG. 4A and FIG. 4B are DVS plots showing water absorption of cysteamine-pantetheine disulfide succinate (2:1 ) salt (FIG. 4A) and cysteamine-pantetheine disulfide malate (2:1 ) salt (FIG. 4B).

FIG. 5A and FIG. 5B are XRPD patterns of cysteamine-pantetheine disulfide succinate (2:1 ) salt (FIG. 5A) and cysteamine-pantetheine disulfide malate (2:1 ) salt (FIG. 5B) after water absorption. DETAILED DESCRIPTION OF THE INVENTION

To identify cysteamine-pantetheine disulfide salts with improved properties, a salt screen was performed with 15 different counterions and 11 different solvent systems. From the salt screen, two salt form candidates (cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt), both amorphous white solids, were found, and their properties further assessed. Following identification of these two salt candidates, an in vivo pharmacokinetic study was performed to determine the ability of these salt forms to maintain an elevated plasma cysteamine concentration, e.g., of at least about 2.5 pM.

Cysteamine-pantetheine disulfide (e.g., in free base form) has the structure:

Cysteamine-pantetheine disulfide may be referred to as TTI-0102. Cysteamine-pantetheine disulfide is a prodrug for cysteamine, and when orally administered to a subject, cysteamine-pantetheine disulfide is first split into one cysteamine and one pantetheine via reduction of the disulfide by a biological reducing agent (e.g., glutathione) in the gastrointestinal (Gl) tract. The pantetheine is then further converted to one cysteamine and one pantothenate, e.g., by pantetheinase (e.g., Vnn1 pantetheinase, also known as Vanin 1 ) in the Gl tract mucosa. Through this process, each molecule of TTI-0102 generates two molecules of cysteamine in vivo, when administered orally. To maintain a plasma cysteamine concentration of at least about 2.5 pM, about 5.5 g of TTI-0102 is needed per day for a > 40 kg subject, and about half that (e.g., about 2.75 g) is needed per day for a < 40 kg subject. Previous in vitro and in vivo studies have demonstrated that cysteamine-pantetheine disulfide exhibits superior PK properties compared to cysteamine, which promotes better patient compliance, and reduces side effects of cysteamine administration, such as halitosis, body odor, and gastrointestinal side effects (e.g., anorexia, nausea, vomiting, and/or stomach pain). This disclosure provides methods for new stable and soluble salt forms of cysteamine-pantetheine disulfide (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) that are useful in therapy, such as in the treatment of a patient having a cysteamine-sensitive disorder. In a preferred embodiment, the salt is a cysteamine-pantetheine disulfide malate (2:1 ) salt.

The free base form of cysteamine-pantetheine disulfide (TTI-0102) is amorphous and is difficult to be isolated in high chemical purity due to poor chemical stability. Thus, better salt forms having better physical and chemical properties and stability are needed. These superior salt forms are provided herein.

Methods of treatment

The present invention relates to cysteamine-pantetheine disulfide salt forms (e.g., cysteamine- pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) and methods useful for treating cysteamine-sensitive disorders. In a preferred embodiment, the salt is a cysteamine-pantetheine disulfide malate (2:1 ) salt. Treatment entails oral administration of cysteamine- pantetheine disulfide salt forms, convertible to cysteamine in the gastrointestinal tract. Cysteamine- pantetheine disulfide, upon reduction in vivo, provides two thiols. Both thiols may be convertible to cysteamine in vivo. Cysteamine-pantetheine disulfide, which provides two thiols in vivo, is a preferred class of therapeutic agents for diseases including cystinosis, cystic fibrosis, malaria, and viral and bacterial infections.

Cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) may be coadministered with agents that enhance the biochemical processes required for (i) in vivo conversion of the precursor to cysteamine and (ii) subsequent absorption of cysteamine by enterocytes. Such enhancers may be selected and dosed to augment or complement the therapeutic effects of cysteamine-pantetheine disulfide in a particular disease, or to individualize a therapeutic regimen for a specific patient. For example, cysteamine-pantetheine disulfide salt forms may be co-administered with reducing agents that enhance disulfide bond reduction. The reducing agent may be a physiological compound such as the thiols glutathione, cysteine, homocysteine, gamma-glutamylcysteine, or it may be an analog of one of those compounds such as N-acetylcysteine, cysteine methyl ester, cysteine ethyl ester or gamma glutamylcysteine ethyl ester, or it may be a dithiol such as dihydrolipoic acid, or a non-thiol reducing agent such as vitamin C (ascorbic acid).

Cysteamine released from the cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) may provide therapeutic effects via any of several mechanisms.

Cysteamine has pleiotropic chemical and pharmacological effects in the body, including (i) antioxidant, (ii) reducing agent and participant in thiol - disulfide exchanges, (iii) enzyme inhibitor and (iv) copper chelator. Cysteamine also modulates plasma levels of certain diseases-associated chemicals and proteins. For example, cysteamine: (v) lowers triglycerides and low density lipoprotein-associated cholesterol, high levels of which have been associated with heart disease and atherosclerosis, and (vi) lowers total adiponectin as well as the relative abundance of adiponectin multimers, high levels of which are associated with metabolic syndrome and other diseases. Cysteamine also has (v) anti-parasitic, (vi) anti-bacterial and (vii) anti-viral effects, as well as (viii) antifibrotic effects, all via uncertain mechanisms.

(i) Cysteamine can act directly as an antioxidant, neutralizing reactive oxygen species (ROS) by providing a reducing group.

(ii) Cysteamine can increase the level of other physiologic antioxidants, including glutathione (GSH), the major antioxidant in the body, and cysteine, an important antioxidant in serum and in the gastrointestinal tract. The antioxidant and GSH-restoring properties of cysteamine are relevant to a broad range of diseases in which high levels of oxidized lipids, proteins or small molecules, often accompanied by low levels of GSH, contribute to pathogenesis. Diseases in which abnormal oxidation products are contributing factors include neurodegenerative diseases, cystic fibrosis and impaired immune function associated with HIV infection (see Herzenberg et al., Proc Natl Acad Sci U SA. 94:1967 (1997); and Bhaskar et al., J Biol Chem. 290:1020 (2015)). GSH, a tripeptide, is degraded to its constituent amino acids by proteases in the gut. Therefore, oral GSH is not an efficient way to deliver GSH to the body. Cysteamine therapy is an effective way to boost GSH levels.

(iii) Cysteamine can chemically reduce, or participate in thiol-disulf ide exchange reactions with glutathione containing disulfide and cysteine containing disulfides (including cystine), thereby producing free glutathione and cysteine, which in turn can reduce other oxidized compounds or neutralize reactive oxygen species. Free cysteine (e.g. generated from cysteamine-cystine exchange) can also be utilized in glutathione synthesis. Cysteamine treatment has been shown to increase total glutathione in both control and cystinotic cells and normalized cystine levels and glutathione (GSH) redox status in cystinotic cells. Cysteamine increases total glutathione and restores glutathione redox status in cystinosis, which is a positive side-effect of this agent next to cystine depletion. In addition to promoting thiol - disulfide exchanges with free cystines and cysteines, cysteamine can also interact with cystine and cysteinyl residues in proteins, including a variety of redox-sensing proteins that control cellular anti-oxidant defense mechanisms. Cysteamine also inhibits pathological cystine accumulation in cystinosis via a thiol-disulfide exchange reaction with lysosomal cystine to form cysteine and cysteine-cysteamine mixed disulfide, both of which can exit lysosomes in the absence of a functional cystinosin gene. (Cysteine-cysteamine disulfide is transported by a lysine I heptahelical protein transporter encoded by the PQLC2 gene.). Cysteamine interacts with cystine (disulfide), mainly stored in the lysosome, to break cystine into two cysteines (thiols), to form a mixed disulfide cysteamine-cysteine, and to export one free cysteine into the cytoplasm. The lysosomes of cystinosis patients lack a functioning lysosomal cysteine membrane transporter and the cysteamine-cysteine disulfide thus formed clears the excess lysosomal cysteine through an alternative amine membrane transporter.

Disorders affecting mitochondria, including those that directly affect the respiratory chain function, have been shown to be associated with impaired redox balance. Peripheral whole blood GSH and GSSG levels are promising biomarkers of mitochondrial dysfunction and may give insights into the contribution of oxidative stress to the pathophysiology of the various mitochondrial disorders. There are potentially two ways to limit the level of ROS in mitochondria: 1 ) decreasing the production of ROS with compounds like quinones (CoQO, Vit E, EPI-743, MitoQ) that interact with the electron transport chain; however, these compounds cannot get into mitochondria very easily in quantity high enough to be really effective; 2) antagonizing ROS with antioxidants. Many antioxidants have been tested to neutralize these ROS but because of the double membrane of the mitochondria, they cannot passively be transported into the mitochondria. Only two antioxidants, glutathione (GSH) and thioredoxin can significantly enter by using a specific transporter. The thiol - disulfide exchange promoted by cysteamine can be used to neutralize ROS in the mitochondria.

(iv) Cysteamine inhibits tissue transglutaminase (also called transglutaminase 2, or TG2), a cytoplasmic enzyme implicated in the pathogenesis of Huntington’s disease. Cystamine, the disulfide of two cysteamines is also a TG2 inhibitor, and has been tested more extensively than cysteamine in Huntington’s disease models. However in the strongly reducing environment of the cytoplasm virtually all cystamine is reduced to cysteamine. Therefore cysteamine is likely the active form of cystamine (see: Jeitner et al., Biochem Pharmacol. 69:961 (2005)). Cystamine improves motor function and extends lifespan in several mouse models of Huntington’s disease. These beneficial effects may be mediated by Brain-Derived Neurotrophic factor (BDNF), which increases upon cystamine treatment. Cystamine also inhibits the cytoplasmic enzyme caspase-3, again likely through cysteamine creation. The abnormal, pathogenic product of the Huntington’s disease gene, huntingtin, induces activation of caspase-3 and consequent release of cytochrome c from mitochondria in cultured cells, ultimately leading to apoptosis. At high concentrations (e.g., 25 millimolar) cysteamine also inhibits matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases with physiologic roles in angiogenesis, wound healing, and tissue remodeling. MMPs are overexpressed in some cancers and contribute to invasion and metastasis by degrading extracellular matrix. Cysteamine inhibits migration and invasion by pancreatic cancer cells in vitro and growth of pancreatic cancer xenografts in vivo (Fujisawa et al., PLoS One. 7:e34437 (2012)).

(v) Cysteamine, like some other thiols, is a strong copper chelator, which can be a cause of major side-effects in some cystinosis patients, who already have low copper and ceruloplasmin levels as a consequence of their disease-associated renal insufficiency. However, copper chelation may be therapeutically beneficial in neurodegenerative diseases, for example Alzheimer’s disease.

(vi) Cysteamine reduces levels of oxidized proteins and inhibits myofibroblast proliferation via TGF-beta independent mechanisms in two mouse models of chronic kidney disease. Myofibroblasts produce extracellular matrix, including collagen, and abnormal myofibroblast proliferation is associated with scarring, contraction and loss of organ function in a variety of chronic fibrotic diseases, including diseases of the kidney (e.g. Alport’s disease, focal segmental glomerulosclerosis), lung (e.g. cystic fibrosis, pulmonary fibrosis, chronic obstructive pulmonary disease) and liver (e.g. non-alcoholic fatty acid liver disease, non-alcoholic steatohepatitis and alcoholic steatohepatitis).

(vii) Cysteamine inhibits proliferation of the parasite that causes malaria, Plasmodium Falciparum, both in vitro and in mouse models of malaria, without adversely modulating host inflammatory responses. Administration of the cysteamine precursor pantethine prevents the cerebral syndrome in mice infected with the Plasmodium berghei ANKA strain. Cysteamine also potentiates the therapeutically important artemisinin family of anti-malarials. In some embodiments artemisinin-cysteamine precursor combinations are used to treat malaria, including emerging artemisinin-resistant Plasmodium strains as well as cerebral malaria. Preferred cysteamine precursors for therapy of malaria are those from which two cysteamines can be generated; that is, disulfide cysteamine precursors in which both of the thiols generated upon reduction are convertible into cysteamine. Exemplary disulfide cysteamine precursors include those formed by joining cysteamine and pantetheine or cysteamine and 4-phosphopantetheine. Preferred enhancers of disulfide bond reduction to be co-administered with disulfide cysteamine precursors include the thiols pantetheine, 4-phosphopantetheine, dephospho-coenzyme A and coenzyme A, each of which is itself a cysteamine precursor.

(viii) Cysteamine promotes multimerization of adiponectin, a signaling molecule produced by adipocytes. Low levels of adiponectin have been associated with insulin resistance and inflammation and may contribute to the pathogenesis of both type I and type II diabetes. High molecular weight adiponectin may help mediate insulin signaling. Pediatric patients with nonalcoholic fatty liver disease (NAFLD) treated with cysteamine for 24 weeks had increased levels of high molecular weight adiponectin multimers. Cysteamine may be therapeutically useful in conditions associated with low adiponectin levels, including insulin-resistant metabolic diseases such as diabetes. In addition to total adiponectin, the distribution of adiponectin multimers can independently explain variability in metabolic traits among individuals and populations.

(ix) Cysteamine has pleiotropic anti-viral effects. For example, it may inhibit HIV replication by interfering with the production of infectious viral particles, by blocking pro-viral DNA formation or by forming mixed disulfides with cysteine residues of proteins, thereby modifying the disulfide bridge architecture of the cell membrane and limiting adsorption of the virus. Cysteamine can also inhibit growth of influenza virus types A, B and C, including avian influenza virus subtypes such as H5N1 , H1 N2, H2N2, H3N2, H3N8, H5N1 , H5N2, H5N3, H5N8, H5N9, H7N1 , H7N2, H7N3, H7N4, H7N7, H9N2, and H10N7. Cysteamine may also inhibit proliferation of Spanish, Asian and Hong Kong influenza virus strains, as well as swine, equine and canine influenza viruses. U.S. Patent No. 8,415,398 discloses anti-viral uses of cysteamine.

In specific diseases cysteamine may act via one of the above mechanisms of action, via multiple mechanisms, or via one or more mechanisms that have not yet been identified.

Diseases and disorders for which there is evidence of cysteamine efficacy include cystinosis; neurodegenerative disease; neurodevelopmental disorders, e.g. Rett syndrome; mitochondrial disorders, e.g., Leigh syndrome, MELAS, MERFF, Friedreich’s ataxia and conditions associated with mutations in the POLG gene, as well as some forms of autism; fibrotic diseases of the kidney (e.g., Alport’s disease, focal segmental glomerulosclerosis (FSGS)), of the liver (e.g. non-alcoholic steatohepatitis (NASH) and alcoholic steatohepatitis (ASH)), and of the lung (pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF)); parasitic infection (e.g., malaria and cerebral malaria); sickle cell anemia; cancer; stroke; bacterial infection, including biofilm-forming bacteria such as Pseudomonas aeruginosa; viral infection, including influenza virus and human immunodeficiency virus infection (AIDS); metabolic diseases including metabolic syndrome X and non-alcoholic fatty liver disease (NAFLD); metal poisoning, including copper and poisoning; and protection against radiation toxicity.

The cysteamine-pantetheine disulfide salt forms of the invention will provide improved treatment for these diseases by allowing better control of cysteamine blood levels (i.e., maintaining cysteamine in the therapeutic range for prolonged periods) and, by providing a second therapeutic thiol moiety, thereby improving efficacy and patient convenience while reducing side effects and patient non-compliance with therapy.

In some instances, methods of treatment include administering cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine- pantetheine disulfide succinate (2:1 ) salt) to a subject in need of treatment. In some instances, the subject has a cysteamine-sensitive disorder described herein. In some instances, a method of treatment described herein includes administering from 50 to 150 milligrams per kilogram of body weight (mg/kg) (e.g., 60±10, 70±10, 80±10, 90±10, 100±25, 110±20, 120±10, 130±10, or 140±10 mg/kg) of a cysteamine-pantetheine disulfide salt form (e.g., a cysteamine-pantetheine disulfide malate (2:1 ) salt or a cysteamine-pantetheine disulfide succinate (2:1 ) salt) to a subject daily. In some instances, a method of treatment described herein includes administering from about 3,000 mg to about 8,500 mg (e.g., about 3,000 mg, about 3,500 mg, about 4,000 mg, about 4,500 mg, about 5,500 mg, about 6,000 mg, about 6,500 mg, about 7,000 mg, about 7,500 mg, about 8,000 mg, or about 8,500 mg) of a cysteamine- pantetheine disulfide salt form (e.g., a cysteamine-pantetheine disulfide malate (2:1 ) salt or a cysteamine- pantetheine disulfide succinate (2:1 ) salt) to a subject daily. In a particular example, the method includes administering about 5,500 mg of a cysteamine-pantetheine disulfide salt form (e.g., a cysteamine- pantetheine disulfide malate (2:1 ) salt or a cysteamine-pantetheine disulfide succinate (2:1 ) salt) to a subject daily. In another particular example, the method includes administering about 4,100 mg of a cysteamine-pantetheine disulfide malate (2:1 ) salt to a subject daily. In another particular example, the method includes administering about 8,200 mg of a cysteamine-pantetheine disulfide malate (2:1 ) salt to a subject daily.

Neurodegenerative Diseases

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat neurodegenerative diseases. Neurodegenerative diseases include Huntington’s disease (HD), Parkinson’s disease (PD), Alzheimer’s disease (AD) and neurodegeneration with brain iron accumulation (NBI A) , also referred to as Hallervorden-Spatz syndrome. These diseases, which are caused to varying degrees by known gene mutations, are characterized by progressive loss of structure or function of neurons, including neuronal death. HD is entirely attributable to expansion of a CAG triplet in exon 1 of the HTT gene, while NBIA is associated with mutations in about 10 genes, the most common being PANK2 (30-50% of cases). A smaller fraction of PD and AD cases are genetic in origin. Neurodegenerative diseases are also associated with a variety of protein misfolding abnormalities (e.g., aggregation of alpha-synuclein, hyperphosphorylation and aggregation of tau protein, and aggregation of beta amyloid protein), as well as misregulation of protein degradation pathways (e.g., the ubiquitin- proteasome pathway and autophagy-lysosome pathways), membrane damage, mitochondrial dysfunction, defects in axonal transport, or misregulation of programmed cell death pathways (e.g., apoptosis and autophagy).

Huntington’s disease (HD) cells have very low levels of the enzyme cystathionine gamma-lyase (CSE), an important generator of cysteine from cystathionine. The defect occurs at the transcriptional level and may be an important mediator of neurodegeneration. Administration of cysteine to HD tissues and to an animal model of HD reverses oxidative stress and other abnormalities. There is also evidence for cysteine efficacy in other neurodegenerative diseases, including neurodegeneration with iron accumulation, Parkinson’s disease, Alzheimer’s disease, and neurodevelopmental disorders, e.g., Rett syndrome and other MECP-2 associated disorders. However, orally administered cysteine has low bioavailability and in large doses may be toxic.

Cysteamine crosses the blood brain barrier, can promote formation of cysteine in vivo (e.g., by thiol-disulfide exchange with cystine), and can provide a source of sulfur for cysteine biosynthesis. Cysteamine has exhibited beneficial effects in three different mouse models of HD. Four studies have shown beneficial effects in the R6/2 mouse model. The R6/2 HD mouse model contains a transgene expressing exon 1 of a mutant human HTT allele with a very long CAG triplet repeat. Beneficial effects of cysteamine include amelioration of weight loss and motor abnormalities, and prolongation of survival. One study has shown benefit in the R6/1 mouse model, which also contains an exon-1 transgene with a smaller expanded CAG repeat and a milder phenotype. Cysteamine has also been shown to be beneficial in the YAC128 mouse model of HD, which contains a full-length HTT gene with an expanded CAG repeat. The mechanism of action of cysteamine is uncertain.

In February 2014, Raptor Pharmaceutical Corp, announced results from a planned 18 month interim analysis of an ongoing 3-year Phase 2/3 clinical trial of RP103 (delayed-release cysteamine bitartrate) in Huntington's disease. A total of 96 patients with HD were randomized to treatment with RP103 or placebo. RP103 treated patients were dosed at 1 ,200 mg cysteamine/day, approximately half the dose used for cystinosis. Eighty-nine patients completed the initial 18 month phase. Analysis of all 96 patients enrolled in the trial showed a positive trend toward slower worsening of Total Motor Score (TMS) in patients treated with RP103, the primary endpoint of the study. TMS progression was 32% slower in patients treated with RP103 vs. those treated with placebo after 18 months treatment (4.51 vs. 6.68 respectively, p=0.19). In 66 patients not taking concurrent tetrabenazine, RP103 treatment resulted in a statistically significant delay in disease progression as measured by TMS when compared to the placebo group (2.84 points vs. 6.78 respectively, p=0.03).

Liver Diseases

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat liver diseases. Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States and Europe and its incidence is increasing rapidly in the Asia-Pacific region. Estimates of NAFLD prevalence in the United States range from 23% to 33.6%. It has been estimated that up to 80% of patients with metabolic syndrome (approximately 47 million people in the United States) may also have NAFLD. In some patients NAFLD progresses to non-alcoholic steatohepatitis (NASH), a potentially lethal disease, and an increasing cause of liver failure, with an estimated prevalence of 2% to 5.7% in the U.S.

There is no FDA-approved treatment for NAFLD, NASH or alcoholic steatohepatitis (ASH). Clinical trials of a variety of agents including the anti-oxidant vitamin E, the hypoglycemic agent metformin and the PPAR gamma agonists pioglitazone and rosiglitazone have yielded disappointing results. Phase 2 clinical trials of the semi-synthetic bile acid derivative obeticholic acid, a farnesoid X receptor agonist, have been promising. Other experimental therapies targeting insulin resistance and are being tested.

In 2011 , Dohil et al. (Aliment Pharmacol. Ther. 33:1036 (2011 )) conducted a small, open-label 24 week pilot trial of enteric-coated cysteamine in 11 children with NAFLD. Cysteamine reduced serum levels of the liver enzymes ALT and AST (indices of hepatocyte damage) in 7 of 11 patients, an effect which persisted for six months after therapy ended. However, there was no effect on body mass index (BMI). This open-label Phase 2a clinical trial involved children with a biopsy-confirmed diagnosis of moderate to severe NAFLD and baseline ALT and AST levels at least twice the upper limit of normal. These patients received enteric-coated cysteamine twice daily for six months, followed by a six-month post-treatment monitoring period. Among all patients there was a mean 54% reduction in ALT (p=0.004), meeting the pre-defined primary endpoint of at least 50% ALT reduction from baseline. In addition, patients saw improvements in secondary endpoints including AST (41% avg reduction, p=0.02), cytokeratin 18 (45% avg reduction, p=0.026), and adiponectin (35% avg reduction, p=0.023). Serum transaminases were measured following drug withdrawal and the reductions in ALT and AST persisted during the 6-month post-treatment phase. Following this proof-of-concept study by Dohil et al., Raptor Pharmaceutical Corp, initiated a clinical trial in cooperation with the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The trial, called Cysteamine Bitartrate Delayed-Release for the Treatment of Non-alcoholic Fatty Liver Disease in Children (CyNCh), has enrolled 160 pediatric participants at ten U.S. centers in the NIDDK-sponsored NASH Clinical Research Network.

CyNCh is a multicenter, double-masked, randomized, placebo-controlled, phase lib clinical trial of treatment with either delayed-release cysteamine (RP103) capsules (300 mg orally twice daily for patients < 65 kg, 375 mg orally twice daily for patients >65-80 kg or 450 mg orally twice daily for patients >80 kg) or placebo for children with histologically-confirmed NAFLD. Cysteamine doses almost 3 times lower than those used to treat cystinosis were possible because first-pass metabolism of cysteamine in the liver removes about 40% of the cysteamine absorbed by the intestine, which is a hurdle for systemic therapy of cysteamine-sensitive diseases but an advantage in the treatment of liver diseases.

Other liver diseases that could benefit from cysteamine therapy include alcoholic steatohepatitis, and acute on chronic liver failure.

Malaria

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat malaria. In vitro and in vivo evidence for the effectiveness of cysteamine in malaria, both as a sole treatment and as a potentiator of artemisinin, is described above. Cysteamine treatment could benefit patients with malaria and cerebral malaria.

Resistance to artemisinin is characterized by significantly delayed clearance of parasites following artemisinin treatment. Artemisinin derivatives have half-lives of the order of an hour, and therefore require at least daily dosing over several days. For example, the WHO-approved adult dose of co-artemether (artemether-lumefantrine) is 4 tablets at 0, 8, 24, 36, 48 and 60 hours (six doses). Due to its similar short half-life, cysteamine could be dosed followed the same schedule if using an immediate release formulation of a cysteamine precursor (i.e. , cysteamine-pantetheine disulfide), or could be dosed every 12 hours for 3 days, at doses similar to the doses used for the treatment of patients with cystinosis, i.e., 2.5 g/day in adults.

Cystinosis

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat cystinosis. Cystinosis is a rare, autosomal recessive inherited lysosomal storage disease. It is the most frequent and potentially treatable cause of the inherited renal Fanconi syndrome. Untreated, kidney function rapidly deteriorates by the end of the first decade of life leading to end-stage renal disease which requires kidney transplantation. Two major milestones in cystinosis management, cystine-depleting therapy with cysteamine and renal allograft transplantation, have had a considerable impact on the prognosis for cystinosis patients. However, compliance with cysteamine therapy has been a major problem due to significant side effects and a strict 6-hourly dosing regimen when using the immediate release formulation of cysteamine bitartrate (Cystagon®). Recently, a new twice-daily delayed-release enteric-coated formula of cysteamine bitartrate (Procysbi®) has been approved by the FDA in the US and by the EMA in Europe, for treatment of cystinosis, and has been shown to be a safe and effective alternative to Cystagon®. The recommended maintenance dose of cysteamine (every 6 hours for the immediate-release formulation, Cystagon®, or twice per day for the delayed-release formulation, Procysbi®) is 1 .3 grams per square meter of body surface area per day. The dose can be increased up to 1 .95 grams/m²/day if the white blood cell cystine level remains higher than 1 nanomolar ¹/2 cystine per milligram of WBC protein. Hereditary Mitochondrial Diseases

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat hereditary mitochondrial diseases. Cysteamine directly scavenges ROS including superoxide free radicles, aldehydes (toxic products of lipid peroxidation) and hydrogen peroxide. Cysteamine also contributes to the formation of other reducing thiols by disulfide bond reduction and by participating in thiol-disulf ide exchange reactions, including reactions with cystine that yield cysteine and cysteinecysteamine mixed disulfide. This reaction increases the cellular cysteine pool. Cysteine is the rate limiting substrate in glutathione (GSH) biosynthesis. Glutathione is a tripeptide composed of the amino acids cysteine, glutamate and glycine.

Low GSH levels compromise mitochondrial function, which may aggravate inherited mitochondrial diseases. Salmi et al. {Scandinavian Journal of Clinical and Laboratory Investigation, 2012) studied a cohort of children with biochemically and/or genetically confirmed mitochondrial diseases and found altered plasma thiol levels and redox state, indicating an increase in oxidative stress and depletion of antioxidant supplies. The ability of cysteamine to increase cellular thiol levels, including cysteine, could potentially address the relative thiol deficiency in patients with mitochondrial diseases. The ability of cysteamine to directly scavenge ROS may counter the increased oxidative stress and improve the compromised mitochondria function in these diseases.

In 2014, Raptor Pharmaceuticals initiated an open label, dose-escalating phase 2 trial with its delayed-release cysteamine, RP103, administered up to 1 .3 g/m²/day in two divided doses, every 12 hours, for up to 6 months in patients with Leigh syndrome and other inherited mitochondrial diseases.

Exemplary inherited mitochondrial diseases include, but are not limited to, Friedreich’s Ataxia, Leber’s hereditary optic neuropathy, myoclonic epilepsy and ragged-red fibers, Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like syndrome (MELAS), Kearn-Sayre syndrome, subacute necrotizing encephalopathy (Leigh’s Syndrome), and mitochondrial cardiomyopathies and other syndromes due to multiple mitochondrial DNA deletions. Additional mitochondrial diseases include neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP), progressive external opthalmoplegia (PEG), and Complex I disease, Complex II disease, Complex III disease, Complex IV disease and Complex V disease, which relates to dysfunction of the OXPHOS complexes. And also, mutations in the POLG gene as well as some forms of autism.

Cystic Fibrosis and Other Chronic Respiratory Conditions

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat cystic fibrosis and other chronic respiratory conditions. Cystic fibrosis (CF) is caused by loss-of-function mutations in the CFTR gene, which encodes a cAMP-regulated chloride channel expressed in a variety of epithelial cells. Defective CFTR function leads to major clinical manifestations including chronic lung inflammation with increased susceptibility to respiratory tract bacterial infections, pancreatic dysfunction and male infertility. A three base deletion mutation, AF508, accounts for about 70-90% of CF in Northern Europe and North America. AF508-CFTR can retain partial chloride channel activity if rescued at the plasma membrane by corrector molecules, but in this case AF508-CFTR is rapidly recycled from the plasma membrane and diverted to lysosomal degradation. Thus, stabilizing AF508-CFTR at the plasma membrane remains a challenging task. Loss of functional CFTR induces reactive oxygen species (ROS)- and transglutaminase 2 -mediated crosslinking of BECN1 and sequestration of phosphatidylinositol 3- kinase (Ptdlns3K) class III within intracellular aggresomes, leading to lung inflammation. Cysteamine can restore BECN1 function and autophagy, reduce SQSTM1 accumulation and blunt inflammation in human cells and in the airways of mouse models homozygous for the AF508-CFTR mutation. Moreover, administration of cysteamine can rescue intracellular trafficking and stabilize a fully functional AF508- CFTR at the plasma membrane of epithelial cells, thus complementing the beneficial effects of CFTR corrector molecules. The effects of cysteamine in rescuing autophagy and controlling inflammation extend well after drug washout, but are abrogated by CFTR depletion during withdrawal. Cysteamine (Lynovex® from Novabiotics®) demonstrated at least comparable mucolytic activity to currently available mucolytic agents. Cysteamine was bactericidal against Pseudomonas aeruginosa and other CF pathogens. Cysteamine activity was not sensitive to high ionic concentrations characteristic of the CF lung. Cysteamine prevented the formation of and disrupted established P. aeruginosa biofilms. Cysteamine was synergistic with conventional CF antibiotics; reversing the antibiotic resistance of CF bacterial pathogens. An oral (gel capsule) form of Lynovex® has completed Phase Ila trials. Novabiotics is developing Lynovex for cystic fibrosis and also for COPD and other chronic respiratory conditions as a single treatment with both mucolytic and anti-microbial effects.

Kidney Diseases

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat kidney diseases. Cysteamine was effective in two mouse models of kidney fibrosis: ureteral stenosis and renal ischemia/reperfusion injury (Okamura et al., J. Am. Soc. Nephrol. 25:43 (2014)). These results suggest previously unrecognized antifibrotic actions of cysteamine via TGF-p-independent mechanisms, including oxidative stress reduction and attenuation of the myofibroblast response to kidney injury.

Fibrosis is also one of the main manifestations of genetic forms of glomerular disease, including focal segmental glomerulosclerosis, Alport’s syndrome and thin base membrane disease.

Hereditary Diseases Caused by Arginine to Cysteine Mutation

Certain hereditary diseases can be treated using the cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt). For example, disease causing mutations include DNA sequence changes that alter the codon for arginine to the codon for cysteine. A subset of such mutations occur in proteins which retain partial function, or which at a minimum are stable enough to be completely synthesized by ribosomes and transported to their normal destination (e.g. the plasma membrane, the mitochondria, the nucleus, etc.). Cysteamine can form a disulfide bond with the aberrant cysteine residue and, in doing so, mimic arginine to some extent, thereby restoring to some degree normal protein function (e.g., see Gahl et al. Am J Med Genet 20:409 (1985)). Thus, any hereditary disease with an arginine to cysteamine change is a candidate for cysteamine precursor therapy. Such diseases include hemophilia A, due to arginine to cysteamine mutation in the factor VIII gene; pure autosomal dominant spastic paraplegia, due to arginine to cysteamine mutation in the CPT1 C gene; spinocerebellar ataxia 35, due to arginine to cysteamine mutation in the TGM6 gene; and many other diseases.

Cardiovascular diseases

The cysteamine-pantetheine disulfide salt forms of the invention can be used to treat cardiovascular diseases (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteaminepantetheine disulfide succinate (2:1 ) salt). Heart disease due to atherosclerosis associated with chronic hypercholesterolemia, and ischemic heart disease are treatable with cysteamine precursors, i.e. , cysteamine-pantetheine disulfide.

Neurodevelopmental Disorders

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat neurodevelopmental disorders. Neurodevelopmental disorders include Rett syndrome and other MECP2 associated disorders.

Other Diseases

The cysteamine-pantetheine disulfide salt forms of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) can be used to treat other diseases. Exposure of erythrocytes from sickle cell anemia patients to cysteamine led to a marked inhibition of sickling under hypoxic conditions, a decrease in mean corpuscular hemoglobin concentration, and a significant increase in oxygen affinity. The oxygen affinity of the cysteamine-treated erythrocytes was less dependent on their mean corpuscular hemoglobin concentration than that of untreated sickle cells.

Antineoplastic effects of cysteamine have been demonstrated in cancer cell lines and xenograft models (Fujisawa et al., PLoS One. e34437 (2012)). Notably, cysteamine prolonged survival of mice in a dose-dependent manner without toxicity. Matrix metalloproteinase activity was significantly decreased in animal xenografts and in cancer cell lines treated with cysteamine.

Long-term cysteamine therapy promotes adiponectin multimerization, suggesting that cysteamine may be therapeutic in conditions associated with insulin-resistance, oxidative stress, and depressed adiponectin levels as well as ischemic injury.

Compositions

The invention features pharmaceutical compositions including a cysteamine-pantetheine disulfide salt form of the invention (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine- pantetheine disulfide succinate (2:1 ) salt) and a pharmaceutically acceptable excipient. In a particular example, the pharmaceutical compositions comprise cysteamine-pantetheine disulfide malate (2:1 ) salt. Examples of pharmaceutically acceptable excipients include, but are not limited to, biocompatible vehicles, adjuvants, additives, and diluents to achieve a composition usable as a dosage form. In some embodiments, the pharmaceutically acceptable salt is stable for at least 1 month (e.g., at least 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, or 18 months, or more) when stored at 2-8 °C. In some embodiments, the pharmaceutically acceptable salt is stable for at least 1 week (e.g., at least 1 , 2, 3, or 4 weeks, at least 1 , 2, 3, 4, 5, or 6 months, or more) when stored at 25 °C and at 60% RH. In some embodiments, the pharmaceutically acceptable salt is stable for at least 3 months (e.g., at least 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 18, 24, 30, 36, 42, 48, or 60 months, or more) when stored at -20 °C.

The pharmaceutical compositions of the invention can include one or more solvents, diluents, or other liquid vehicle, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, and lubricants, as suited to the particular dosage form desired. Remington’s Pharmaceutical Sciences, Eighteenth Edition, E. W. Martin (Mack Publishing Co., Easton, Pa., 1990) discloses various excipients used in formulating pharmaceutical compositions and known techniques for the preparation thereof. Except insofar as any conventional excipient medium is incompatible with the compounds of the invention, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the pharmaceutical composition, its use is contemplated to be within the scope of this invention. Some examples of materials which can serve as pharmaceutically acceptable excipients include, but are not limited to, sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients such as cocoa butter and suppository waxes; oils such as peanut oil, cottonseed oil; safflower oil, sesame oil; olive oil; corn oil and soybean oil; glycols; such as propylene glycol; esters such as ethyl oleate and ethyl laurate; agar; natural and synthetic phospholipids, such as soybean and egg yolk phosphatides, lecithin, hydrogenated soy lecithin, dimyristoyl lecithin, dipalmitoyl lecithin, distearoyl lecithin, dioleoyl lecithin, hydroxylated lecithin, lysophosphatidylcholine, cardiolipin, sphingomyelin, phosphatidylcholine, phosphatidyl ethanolamine, diastearoyl phosphatidylethanolamine (DSPE) and its pegylated esters, such as DSPE-PEG750 and, DSPE- PEG2000, phosphatidic acid, phosphatidyl glycerol and phosphatidyl serine; and hydroxypropyl-beta- cyclodextrin and sulfonic acid substituted cyclodextrin (e.g., CAPTISOL™). Commercial grades of lecithin which are preferred include those which are available under the trade name Phosal® or Phospholipon® and include Phosal 53 MCT, Phosal 50 PG, Phosal 75 SA, Phospholipon 90H, Phospholipon 90G and Phospholipon 90 NG; soy-phosphatidylcholine (SoyPC) and DSPE-PEG2000 are particularly preferred; buffering agents such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer’s solution; 5% dextrose solution and combinations with the foregoing aqueous solutions; ethyl alcohol, and phosphate buffer solutions, as well as other non-toxic compatible lubricants such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, releasing agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the composition, according to the judgment of the formulator.

The above-described compositions, in any of the forms described above, can be used for treating a disease or condition described herein. An effective amount refers to the amount of an active compound/agent (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt) that is required to confer a therapeutic effect on a treated subject. Effective doses will vary, as recognized by those skilled in the art, depending on the types of diseases treated, route of administration, excipient usage, and the possibility of co-usage with other therapeutic treatment. A pharmaceutical composition of this invention can be administered parenterally, orally, nasally, rectally, topically, or buccally. The term “parenteral” as used herein refers to subcutaneous, intracutaneous, intravenous, intramuscular, intraarticular, intraarterial, intrasynovial, intrasternal, intrathecal, intralesional, or intracranial injection, as well as any suitable infusion technique. In preferred embodiments, a pharmaceutical composition of this invention is administered orally.

A composition (e.g., a pharmaceutical composition) for oral administration can be any orally acceptable dosage form including powders, microcapsules, sachets, capsules, tablets, emulsions and aqueous suspensions, dispersions, and solutions. In the case of tablets, commonly used excipients include, but are not limited to, lactose and corn starch. Lubricating agents, such as, but not limited to, magnesium stearate, also are typically added. For oral administration in a capsule form, useful diluents include, but are not limited to, lactose and dried corn starch. When aqueous suspensions or emulsions are administered orally, the active ingredient can be suspended or dissolved directly into an aqueous solution or suspended or dissolved in an oily phase combined with emulsifying or suspending agents. If desired, certain sweetening, flavoring, or coloring agents can be added. In some instances, the pharmaceutical composition is formulated as a tablet. In some instances, the pharmaceutical composition is formulated as a sachet. In some instances, the pharmaceutical composition is formulated as a powder.

In some instances, the pharmaceutical composition is formulated in unit dosage form. In some embodiments, the unit dosage form is formulated as a powder, a sachet, a capsule, a solution, or a tablet. In some embodiments, the unit dosage form comprises about 100 mg, about 200 mg, about 250 mg, about 500 mg, about 750 mg, about 1 ,000 mg, about 1 ,500 mg, about 2,000 mg, about 2,500 mg, about 3,000 mg, about 4,000 mg, about 5,000 mg, about 5,500 mg, about 6,000 mg, about 6,500 mg, about 7,000 mg, about 7,500 mg, about 8,000 mg, or about 8,500 mg of an active compound/agent (e.g., cysteamine-pantetheine disulfide malate (2:1 ) salt and cysteamine-pantetheine disulfide succinate (2:1 ) salt). In a particular embodiment, the unit dosage form comprises about 4,100 mg of a cysteamine- pantetheine disulfide malate (2:1 ) salt). In another particular embodiment, the unit dosage form comprises about 8,200 mg of a cysteamine-pantetheine disulfide malate (2:1 ) salt).

The above-described compositions (e.g., pharmaceutical compositions), in any of the forms described above, may be stored in a light impenetrable container. For example, the compositions described herein may be contained in an amber bottle.

EXAMPLES

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the methods and compounds claimed herein are performed, made, and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention.

Example 1. Salt Screen

A trifluoroacetate (TFA) salt and an HCI salt were prepared for cysteamine pantetheine disulfide (TTI-0102) during synthesis. However, these two salts showed poor physical and chemical properties and poor stability. Both the TFA and HCI salts were glassy solids at -20 °C and converted to sticky material at room temperature. The HCI salt also exhibited low chemical purity due to poor chemical stability. The HCI salt decomposed quickly in aqueous media (data not shown). Although the TFA salt exhibited better chemical purity and stability, the TFA counter ion is not pharmaceutically acceptable. Therefore, the objective of the salt screening was to identify a pharmaceutically acceptable salt form with good physical and chemical properties and stability. Main criteria of the salt selection include stability, hygroscopicity, and molecular weight of counter ion. Because the free form is chemically unstable, the TFA salt was used as the starting material to synthesize the other salt forms used in the salt screen.

Dissolved cysteamine-pantetheine disulfide was separately combined with 15 organic and inorganic acids, see Table 1 . About 60 mg of each acid in Table 1 was dissolved in 6 mL of MeOH, EtOH, water, acetone, or acetonitrile to obtain about 10 mg/mL acid solution to exchange with AMBERLITE® IRA- 67. Then the acid-exchanged AMBERLITE® was washed by the corresponding solvent. 30 mg of cysteamine-pantetheine disulfide TFA salt was dissolved in 6 mL solvent, the solution was used to ionexchange with the acid-exchanged AMBERLITE®. Ion-exchanged samples were collected and were investigated by high performance liquid chromatograph (HPLC), ion chromatography (IC) and nuclear magnetic resonance (NMR).

About 100 mg of L-malic acid was dissolved in 11 mL of MeOH or water to obtain about 9mg/mL acid solution to exchange with AMBERLITE® IRA-67. Then the acid-exchanged AMBERLITE® was washed by the corresponding solvent. 10Omg of cysteamine-pantetheine disulfide (TTI-0102) TFA salt, was dissolved in 20mL solvent, the solution was used to ion-exchange with the acid-exchanged AMBERLITE®. Ion-exchanged samples were collected and were investigated by HPLC, IC and 1 H-NMR.

Table 1. List of acids used in cysteamine-pantetheine disulfide salt screen

In total, about 40 salt screening experiments were conducted, followed by about 90 crystallization experiments. From these studies 9 salt candidates were identified. IC or ¹H-NMR was used to determine stoichiometry of the salt candidates: fumarate (1 :0.5), maleate (1 :0.5), succinate (1 :0.5), hippurate (1 :0.5), pamoate (1 :3), HCI (1 :1 ), acetate (1 :1 ), glycolate (1 :1 ), and L-malate (1 :0.5). Liberation of TTI-0102 free base form was also tried, but the free form showed severe degradation with only 69%~78% chemical purity after liberation by using strong basic ion exchange resin (Amberlite ©IRA-402 resin). If weak basic ion exchange resin (Amberlite ©IRA-67 resin) is used instead, TFA counter ion cannot be fully exchanged.

HPLC was used to determine purity for potential salt candidates: for HCI (76.8% purity after lyophilization), acetic acid (96.2% purity after lyophilization ), glycolic acid (96.7% purity after lyophilization ), fumaric acid (97.1 % purity after lyophilization ), maleic acid (89.6% purity after lyophilization ), succinic acid (97.3% purity after lyophilization ), and L-malic acid (96.3% purity after lyophilization ).

Among the 9 salt candidates, the hippurate salt and the pamoate salt were not selected because of the high molecular weight of the counter ion, which is undesirable for use in pharmaceutical compositions with especially high dosing burdens. The HCI salt was eliminated from consideration because although the HCI salt was chemically stable during ion exchange, severe degradation occurred after drying by lyophilization (see above). The other 6 salt hits, including the mono-acetate salt, the hemifumarate salt, the hemi-maleate salt, the hemi-succinate salt, the hemi-L-malate salt, and the monoglycolate salt showed good chemical purity (>95%) after lyophilization, but they were all amorphous. Therefore, these 6 salt hits were scaled up for further crystallization.

Crystallization was performed in 11 solvent systems (methanol (MeOH), ethanol (EtOH), acetone, acetonitrile (ACN), EtOH/ACN (4:96, v:v), EtOH/ACN (1 :3, v:v), EtOH/Acetone (1 :3, v:v), EtOH/Acetone (4:96, v:v), MeOH/ACN (1 :6, v:v), toluene, or methyl ethyl ketone (MEK). Most combinations did not afford a solid product even after cooling (i.e ., equilibrated in 0.1 ~0.15 mL of solvents at 5 °C with a stirring bar on a magnetic stirring plate at a rate of 400 rpm. Obtained suspensions were filtered through a 0.45 pm nylon membrane filter by centrifugation at 14,000 rpm.); re-slurrying (i.e., 0.1 ml of solvent (e.g., MEK, toluene, heptane, ethyl acetate (EA), dichloromethane (DCM), methyl tert-butyl ether (MTBE), hexane, or isopropyl acetate (IPAc)) was added and then re-slurried with a rate of 400 rpm at 5 °C. Obtained suspensions were filtered through a 0.45pm nylon membrane filter by centrifugation at 14,000 rpm.); antisolvent addition (i.e., 2-7 folds of anti-solvent was added into the clear solutions slowly until a large amount of solids precipitated out); or salt metathesis (i.e., about 50 mg of the TTI-0102 trifluoroacetate salt, 1 :1 equiv. of NaOH and 1 :1 equiv. of counter ions were added into 0.1 mL-0.3 mL of water in a 2 mL glass vial. Obtained mixtures were stirred at 5 °C for at least 48 hours. Obtained suspensions were filtered through a 0.45 pm nylon membrane filter by centrifugation at 14,000 rpm.).

About 90 crystallization experiments were conducted with multiple crystallization methods including equilibration, anti-solvent addition and re-slurry. However, none of the salts could be crystallized. Among these amorphous salts, the mono-acetate salt, the hemi-fumarate salt, the hemi- maleate salt, and the mono-glycolate salt were either sticky or converted to sticky material under ambient condition (20-25 °C, 60%-70% relative humidity (RH)) within 1 hour, while the hemi-succinate salt and the hemi-L-malate salt maintained a hard glassy solid state after exposure to ambient condition (20-30 °C, 30%-40% RH) for 1 day. Therefore, the hemi-succinate salt and the hemi-L-maleate salt were selected as salt candidates for scale-up and evaluation in terms of stability and hygroscopicity.

Example 2. Salt Candidate Preparation for Succinate and Malate Salts of Cysteamine-Pantetheine Disulfide (TTI-0102)

Scaled- Up Preparation of Salt Candidates

500-mg- and 800-mg-scale preparations of the succinate and malate salts were prepared as follows.

500 mg succinate: 1 .2g of succinic acid was dissolved in 120 mL of water to obtain a 10 mg/mL acid solution. The obtained solution was exchanged with 40 g AMBERLITE® IRA-67 at 25°C for 13 days. Then 20 g acid-exchanged AMBERLITE® was washed by 240 mL of water. 527mg of TTI-0102 TFA salt, was weighed and then dissolved in 80mL of water. The TTI-0102 TFA salt solution was used to ion exchange with 20g acid-exchanged AMBERLITE® (wash 5 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 5 times). Additional succinic acid was added into the clear solution to obtain a clear solution. The obtained clear solution was then treated by freeze drying for about 3 days. Then white solid was obtained. It remains white solid state after exposure to ambient condition (20-30 °C, 30%-40% relative humidity (RH)) within 1 day.

500 mg malate: 1 .2g of L-malic acid was dissolved in 120 mL of water to obtain a 10 mg/mL acid solution. The obtained solution was exchanged with 40 g AMBERLITE® IRA-67 at 25 °C for 12 days. Then the 30 g acid-exchanged AMBERLITE® was washed by 360mL of water. 527 mg of TTI-0102 TFA salt was weighed and then dissolved in 80 mL of water. The TTI-0102 TFA salt solution was used to ion exchange with about 10 g acid-exchanged AMBERLITE® (wash 10 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 3 times). Additional L-malic acid was added into the clear solution to obtain a clear solution. The obtained clear solution was then treated by freeze drying for about 3 days. Then white solid was obtained. It remains white solid state after exposure to ambient condition (20-30 °C, 30%-40% RH) within 1 day.

800 mg succinate: 1 .2 g of succinic acid was dissolved in 120 mL of water to obtain a 10 mg/mL acid solution. The obtained solution was exchanged with 40 g AMBERLITE® IRA-67 at 25°C for 2 days. Then 20 g acid-exchanged AMBERLITE® was washed by 240mL of water. 81 Omg of TTI-0102 TFA salt was weighed and then dissolved in 162 mL of water. The TTI-0102 TFA salt solution was used to ion exchange with 20 g acid-exchanged AMBERLITE® (wash 5 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 5 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 5 times). Additional succinic acid was added into the clear solution to obtain a clear solution. The obtained clear solution was then treated by freeze drying for about 2 days. A white solid was obtained.

800 mg malate: 1 .2 g of L-malic acid was dissolved in 120 mL of water to obtain a 10 mg/mL acid solution. The obtained solution was exchanged with 40 g AMBERLITE® IRA-67 at 25 °C for 2 days. Then the 20 g acid-exchanged AMBERLITE® was washed by 240 mL of water. 810 mg of TTI-0102 TFA salt was weighed and then dissolved in 120 mL of water. The TTI-0102 TFA salt solution was used to ion exchange with about 20 g acid-exchanged AMBERLITE® (wash 6 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 5 times). Then the obtained solution was used to ion exchange with another 10 g acid-exchanged AMBERLITE® (wash 5 times). Additional L-malic acid was added into the clear solution to obtain a clear solution. The obtained clear solution was then treated by freeze drying for about 2 days. A white solid was obtained.

Chemical and Physicochemical Properties of Salt Candidates

Chemical and physicochemical properties of the succinate and malate salts were determined and summarized below in Table 2.

Table 2. Chemical and Physicochemical Properties

Physical Form

Residual solvent(s) by ¹H-NMR

XRPD diffractograms were collected using the parameters described below in Table 3:

Table 3. X-Ray Powder Diffraction (XPRD) Parameters

Bulk Stability of Salt Candidates

The succinate salt and L-malate salt were each placed at 25 °C/60% RH in an open container, and at 40 °C in a closed container for 3 days. Samples after the stress were characterized by HPLC and inspected for color change. Results are summarized below in Table 4. Table 4. Stability: purity and appearance

Values relative to initial purity at time = 0.

The hemi-succinate salt showed 1 .5% and 4.9% chemical purity decrease after stressed at 25 °C/60% RH and 40 °C after 3 days, respectively. The L-malate salt showed 0.4% and 1 .7% chemical purity decrease after stressed at 25 °C/60% RH and 40 °C after 3 days, respectively. Thus, the L-malate salt exhibited higher stability than the succinate salt.

Example 3. Analysis of Succinate and Malate Salts of Cysteamine-Pantetheine Disulfide (TTI- 0102)

Solution Stability of Salt Candidates

Succinate salt and L-malate salt were each dissolved in selected solvents and placed at room temperature (20-25 °C) for 1 day. Solutions after 1 day were investigated by HPLC.

Both the hemi-succinate salt and the hemi-L-malate salt were chemically stable in methanol or ethanol at room temperature (25-30 °C) over 1 day. They were chemically unstable in acetone, EA, DCM or THF with about 21%-77% purity decrease after 1 day.

Hygroscopicity of Salt Candidates and Stability Under Stress

Hygroscopicity of the salt candidates were determined. Results are shown in Table 5 and Table 6.

Table 5. Hygroscopicity Test 1

Hyg oscopicity by Dynamic Vapor Sorption (DVS) at 25°C dm/dt=0.002%

Physical Form

Table 6. Hygroscopicity Test 2

Hyg oscopicity by DVS at 25°C dm/dt=0.002%

Physical Form

Slightly hygroscopic water update > 0.2% but < 2%

Moderately hygroscopic water uptake > 2% but < 15% Water uptake=water sorption in a specific RH (80% to 95%) - water sorption in 40% RH

The criteria are modified from the European Pharmacopeia criteria for hygroscopicity. (Characters Section in Monographs. European Pharmacopoeia 6, Version 6.8, Section 5. 11th ed. Strasbourg, France: European Directorate for the Quality of Medicines & Healthcare (EDQM); 2010) The malate salt of cysteamine-pantetheine disulfide was found to be less hygroscopic than the succinate salt at RH above 40%.

Identification of the hemi-succinate salt and the hemi-L-malate salt greatly improved the chemical stability issue of TTI-0102 relative to the free base form. The two salts were prepared in high chemical purity and remained chemically stable at -20°C after 3 days. Additionally, the hemi-L-malate salt had good counter ion safety and reasonable stoichiometry. Example 4. Additional Stability Analysis of the Malate Salt of Cysteamine-Pantetheine Disulfide (TTI-0102)

The L-malate salt of cysteamine-pantetheine disulfide (TTI-0102) was analyzed for stability when stored at different conditions.

The L-malate salt form was found to be stable for at least 1 month when stored at 2-8 °C. The L- malate salt form was found to be stable for at least 1 month when stored at 25 °C and at 60% RH. The L- malate salt form was found to be stable for at least 3 months when stored at -20 °C. Stability was determined by quantifying % degradation as determined by an HPLC purity test (e.g., < 5% degradation). Data not shown.

OTHER EMBODIMENTS

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each independent publication or patent application was specifically and individually indicated to be incorporated by reference.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure that come within known or customary practice within the art to which the invention pertains and may be applied to the essential features hereinbefore set forth, and follows in the scope of the claims.

Other embodiments are within the claims.

Claims

What is claimed is: CLAIMS

1 . A pharmaceutically acceptable salt of cysteamine-pantetheine disulfide, wherein said pharmaceutically acceptable salt is a 2:1 malate salt.

2. A pharmaceutical composition comprising a cysteamine-pantetheine disulfide salt of claim 1 and a pharmaceutically acceptable excipient.

3. The pharmaceutical composition of claim 2, wherein the pharmaceutical composition is formulated in unit dosage form.

4. The pharmaceutical composition of claim 3, wherein the unit dosage form comprises about 500 mg, about 1 ,000 mg, about 2,000 mg, about 2,500 mg, about 4,100 mg, about 5,500 mg, or about 8,200 mg.

5. The pharmaceutical composition of any one of claims 2-4, wherein the pharmaceutical composition is formulated as a powder, a sachet, microcapsules, a liquid, or a suspension.

6. The pharmaceutical composition of any one of claims 2-5, wherein the pharmaceutical composition is formulated for oral administration.

7. A method of treating a cysteamine-sensitive disorder a subject in need thereof, the method comprising administering to the subject a pharmaceutical composition of any one of claims 2-6 in an amount sufficient to treat the cysteamine-sensitive disorder.

8. The method of claim 7, wherein the cysteamine-sensitive disorder is cystinosis; neurodegenerative disease; neurodevelopmental disease; neuropsychiatric disease; mitochondrial disease; fibrotic diseases of the kidney, of the liver, or of the lung; parasitic disease; sickle cell disease; cancer; ischemic disease including stroke; chronic obstructive pulmonary disease (COPD); cystic fibrosis (CF); bacterial infection; viral infection; non-alcoholic steatohepatitis (NASH); alcoholic steatohepatitis; or non-alcoholic fatty liver disease (NAFLD).

9. The method of claim 8, wherein the cysteamine-sensitive disorder is NASH.

10. The method of claim 8, wherein the cysteamine-sensitive disorder is a neurodegenerative disease selected from Huntington's disease, neurodegenerative disorders with brain iron accumulation, Parkinson's disease, and Alzheimer's disease.

11 . The method of claim 8, wherein the cysteamine-sensitive disorder is a neurodevelopmental disorder selected from Rett syndrome and other disorders associated with MECP2 mutation.

12. The method of claim 11 , wherein the neurodevelopmental disorder is Rett syndrome.

13. The method of claim 8, wherein the cysteamine-sensitive disorder is a mitochondrial disease selected from Leigh syndrome, MELAS, MERFF, and Friedreich's ataxia.

14. The method of claim 13, wherein the mitochondrial disease is MELAS.

15. The method of claim 8, wherein the cysteamine-sensitive disorder is a fibrotic disease selected from Alport's disease, focal segmental glomerulosclerosis (FSGS), alcoholic steatohepatitis (ASH), and pulmonary fibrosis.

16. The method of claim 8, wherein said cysteamine-sensitive disorder is a bacterial infection or viral infection.

17. The method of any one of claims 7-16, wherein the amount sufficient to treat the cysteaminesensitive disorder is about 5.5 g or about 8.2 mg per day.

18. The method of any one of claims 7-17, wherein the pharmaceutical composition is administered orally.

19. The pharmaceutically acceptable salt of claim 1 , wherein the pharmaceutically acceptable salt is stable for at least 1 months when stored at 2-8 °C.

20. The pharmaceutically acceptable salt of claim 1 , wherein the pharmaceutically acceptable salt is stable for at least 1 months when stored at 25 °C and at 60% RH.

21 . The pharmaceutically acceptable salt of claim 1 , wherein the pharmaceutically acceptable salt is stable for at least 3 months when stored at -20 °C.

22. Use of the pharmaceutically acceptable salt of claim 1 or the pharmaceutical composition of any one of claims 2-6 in the manufacture of a medicament for use in a method of treating a cysteaminesensitive disorder a subject in need thereof.

23. Use of the pharmaceutically acceptable salt of claim 1 or the pharmaceutical composition of any one of claims 2-6 for treating a cysteamine-sensitive disorder a subject in need thereof.

24. The pharmaceutically acceptable salt of claim 1 or the pharmaceutical composition of any one of claims 2-6 for use in a method of treating a cysteamine-sensitive disorder a subject in need thereof.