HK1230197A1 - Compounds for treating spinal muscular atrophy - Google Patents

Description

Compounds for the treatment of spinal muscular atrophy

Brief introduction to the drawings

The present invention provides compounds that are modulators of SMN2 gene splicing, their manufacture, pharmaceutical compositions containing them and their use as medicaments for the treatment of Spinal Muscular Atrophy (SMA).

In particular, the present invention relates to compounds of formula (I) and pharmaceutically acceptable salts thereof

A, R therein¹、R²And R³As described herein.

Background

Spinal Muscular Atrophy (SMA) describes in its broadest sense a variety of inherited and acquired Central Nervous System (CNS) diseases characterized by progressive motor neuron injury in the spinal cord and brainstem, which cause muscle weakness and atrophy. The most common form of SMA is caused by mutations in the motor neuron Survival (SMN) gene and appears to affect a wide range of severity from infancy to adulthood (Crawford and Pardo, neurobiol. dis.,1996,3: 97).

Infant SMA is the most severe form of this neurodegenerative disorder. Symptoms include muscle weakness, low muscle tone, crying weakness, a tendency to lame or fall, difficulty sucking or swallowing, accumulation of secretions in the lungs or throat, difficulty eating, and increased sensitivity to respiratory infections. The legs tend to be weaker than the arms and may not reach developmental signs such as head-up or sitting-up. Generally, the earlier the symptoms appear, the shorter the lifespan. Symptoms appear shortly thereafter due to motor neuron cell deterioration. The severe forms of the disease are fatal and there is no known cure for all forms. The progression of SMA is directly related to the rate of motor neuron cell deterioration and the resulting severity of weakness. Infants with severe forms of SMA often die of respiratory illness due to the inability of the muscles that support breathing. Children with lighter forms of SMA survive longer, but they may require extensive medical support, especially for those patients at the more severe end of the spectrum of conditions. The clinical spectrum of SMA disorders has been divided into the following five groups.

(a) SMA type 0 (intra-uterine SMA) is the most severe form of the disease and begins before birth. Generally, the first symptom of SMA type 0 is a reduction in fetal movement that can be observed first between 30 and 36 weeks of gestation. After birth, these newborns rarely move and have difficulty swallowing and breathing.

(b) Type l SMA (infantile SMA or virdnig-Hoffmann disease) develops symptoms between 0 and 6 months, and this type of SMA is also very severe. The patient never achieves a sit-up and death usually occurs in the first 2 years due to the absence of respiratory support.

(c) The onset age of type 2 SMA (transitive SMA) is 7-18 months. The patient is able to sit unsupported but is unable to stand or walk independently. The prognosis for this group depends largely on the degree of respiratory correlation.

(d) Type 3 SMA (juvenile SMA or Kugelberg-Welander disease) is usually diagnosed after 18 months. Type 3 SMA individuals are capable of walking independently at certain times during the course of the disease, but will typically rely on a wheelchair during adolescence or adulthood.

(e) Type 4 SMA (adult-onset SMA). Weakness usually begins in the tongue, hands or feet late in puberty and then progresses to other areas of the body. The process of adult SMA is slower and has little or no effect on life expectancy.

SMN gene maps have been obtained by linkage analysis of complex regions in chromosome 5 q. In humans, this region contains about 50 ten thousand base pairs (kb) of inverted replication, resulting in the production of two nearly identical copies of the SMN gene. SMA is caused by an inactivating mutation or deletion of the telomeric copy of the gene (SMN1) on both chromosomes, resulting in loss of function of the SMN1 gene. However, all patients retained centromeric copies of the gene (SMN2), and the copy number of SMN2 gene in SMA patients was often inversely correlated with disease severity; i.e., patients with less severe SMA have more copies of SMN 2. Nonetheless, SMN2 was unable to fully compensate for the loss of SMN1 function due to alternative splicing of exon 7 by a translationally silent C to T mutation in exon 7. Thus, most transcripts produced by SMN2 lack exon 7(Δ 7 SMN2) and encode truncated SMN proteins that have impaired function and are rapidly degraded.

SMN proteins are thought to play a role in RNA processing and metabolism, with well-identified functions that mediate the assembly of a specific class of RNA-protein complexes known as snrnps. In motor neurons, SMN may have other functions, however, its role in preventing selective degeneration of motor neurons has not been well established.

In most cases, SMA is diagnosed based on clinical symptoms and by the presence of at least one SMN1 gene copy test. However, in about 5% of cases SMA is caused by mutations in genes other than SMN1 inactivation, some of which are known and others not yet identified. In some cases, when the SMN1 gene test is not feasible or does not show any abnormalities, other tests such as Electromyography (EMG) or muscle biopsy may be indicated.

Currently, medical care of SMA patients is limited to supportive therapy, including respiratory, nutritional, and rehabilitation care; no known drug can solve the underlying cause of the disease. Current treatments for SMA consist of preventing and controlling the secondary effects of chronic motor unit loss. The major control problem in SMA type i is the prevention and early treatment of pulmonary problems, which are responsible for death in most cases. Although some infants with SMA grow to adulthood, patients with SMA type 1 have a life expectancy of less than two years.

Several mouse models of SMA have been developed. Specifically, the SMN Δ exon 7(Δ 7 SMN) model (Le et al, hum. mol. gene., 2005,14:845) carried several copies of the SMN2 gene and Δ 7 SMN2cDNA and reproduced the various phenotypic characteristics of type 1 SMA. The Δ 7 SMN model can be used for SMN2 expression studies and assessment of motor function and survival. The C/C-allelic mouse model (Jackson Laboratory strain #008714, The Jackson Laboratory, BarHarbor, ME) provides a less severe model of SMA disease, in which mice have low levels of SMN2 full-length (FL SMN2) mRNA and SMN protein. The C/C-allele mouse phenotype has the SMN2 gene and the mixed mSMNL-SMN2 gene that has been alternatively spliced, but does not have significant muscle weakness. The C/C-allele mouse model was used for SMN2 expression studies.

Due to the increased understanding of the genetic basis and pathophysiology of SMA, several therapeutic strategies have been developed, but none have yet shown success in the clinic.

Gene replacement of SMN1 using viral delivery vectors and use of differentiated SMN1^+/+Cellular replacement of stem cells has shown efficacy in animal models of SMA. Before these methods can be applied to humans, more research is needed to determine safety and immune responses and to address the need to initiate treatment at the neonatal stage.

Use of synthetic nucleic acids as therapeutic agents: (i) antisense oligonucleotides that target sequence elements in SMN2 pre-mRNA and divert the results of the splicing reaction to produce full-length SMN2 mRNA (passsini et al, sci.trans.med., 2011,3:72ra 18; and Hua et al, Nature,2011,478: 123); and (ii) trans-spliced RNA molecules (Coady and Lorson, jneurosci, 2010,30:126) that provide for the replacement of the fully functional RNA sequence of the mutant fragment during splicing and produce full-length SMN1 mRNA also achieved the correction of alternative splicing of SMN2 in cultured cells.

Other approaches being investigated include the search for drugs that increase SMN levels, enhance residual SMN function, or compensate for their loss. Aminoglycosides have been shown to enhance the expression of stable SMN protein produced from Δ 7 SMN2 mRNA by promoting translational readthrough of the aberrant stop codon, but have poor central nervous system penetration and are toxic after repeated dose administration. Chemotherapeutic agents such as aclarubicin have been shown to increase SMN protein in cell culture; however, the toxic characteristics of these drugs prevent long-term use in SMA patients. Some drugs being clinically investigated for the treatment of SMA include transcription activators such as histone deacetylase ("HDAC") inhibitors (e.g., butyrate, valproic acid, and hydroxyurea) and mRNA stabilizers (mRNA decapping inhibitor RG3039 from Repligen) which aim to increase the amount of total RNA transcribed from the SMN2 gene. However, the use of HDAC inhibitors or mRNA stabilizers does not address the underlying cause of SMA and may lead to a global increase in transcription and gene expression in humans, which has potential safety issues.

In an alternative approach, neuroprotective agents such as orlistat (Olesoxime) have been selected for study. These strategies do not target SMN for the treatment of SMA, but rather are developed to protect SMN-deficient motor neurons from neurodegeneration.

Systems designed to identify compounds that increase the inclusion of exon 7 of SMN in RNA transcribed from the SMN2 gene and certain benzols identified thereby have been described in international patent application WO2009/151546a1Azole and benzisohAn azole compound. Compounds designed to cause ribosome frameshifting to produce stabilized SMN proteins from Δ 7 SMN2 mRNA and certain isoindolinone compounds identified thereby have been described in international patent applications WO2010/019236a1 and WO2013/119916a 2.

Despite advances in understanding the genetic basis and pathophysiology of SMA, there remains a need to identify compounds that alter the course of spinal muscular atrophy, one of the most devastating neurological diseases in children.

Detailed Description

Unless defined otherwise, 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. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below.

All publications, patent applications, patents, and references mentioned herein are incorporated by reference in their entirety.

Unless otherwise indicated, the nomenclature used in this application is based on the IUPAC systematic nomenclature.

Any open valency appearing on a carbon, oxygen, sulfur or nitrogen atom in the structures herein indicates the presence of hydrogen, unless otherwise indicated.

The definitions set forth herein apply regardless of whether the terms in question appear alone or in combination. It is contemplated that the definitions described herein may be appended to form chemically relevant combinations, such as, for example, "heterocycloalkylaryl," haloalkylheteroaryl, "" arylalkyl heterocycloalkyl, "or" alkoxyalkyl. The last member in the combination is the group attached to the rest of the molecule. The other members of the combination being attached to the binding group in reverse literal order, e.g. combination amino-C_1-7Alkyl means C substituted by amino_1-7-alkyl, or for example, a combination arylalkyl heterocycloalkyl, refers to a heterocycloalkyl substituted with an aryl-substituted alkyl.

The term "moiety" refers to an atom or a combined group of atoms that is linked to another atom or molecule by one or more chemical bonds, thereby forming part of a molecule. For example, variable A, R of formula (I)¹、R²And R³Refers to a moiety attached to the core structure of formula (I) by a covalent bond.

The term "one or more" when referring to the number of substituents refers to the range from one substituent to the highest possible number of substitutions, i.e., one hydrogen is substituted by a substituent to all hydrogens are substituted by a substituent.

The term "optional" or "optionally" means that the subsequently described event or circumstance may, but need not, occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

The term "substituent" refers to an atom or group of atoms that replaces a hydrogen atom on a parent molecule.

The term "substituted" means that the specified group bears one or more substituents. In the case where any group may carry multiple substituents and multiple possible substituents are provided, the substituents may be independently selected and need not be the same. The term "unsubstituted" means that the indicated group bears no substituents. The term "optionally substituted" means that the specified group is unsubstituted or substituted with one or more substituents independently selected from the group of possible substituents. The term "one or more" when indicating the number of substituents means from one substituent to the maximum number of substitutions possible, i.e., one hydrogen is substituted by a substituent to all hydrogens are substituted by a substituent.

The terms "compound of this invention" and "compound of the invention" refer to compounds as disclosed herein and stereoisomers, tautomers, solvates, and salts (e.g., pharmaceutically acceptable salts) thereof.

When the compounds of the present invention are solids, it will be understood by those skilled in the art that these compounds and solvates and salts thereof may exist in different solid forms (particularly different crystalline forms), all of which are contemplated to be within the scope of the present invention and the specified formula.

The term "pharmaceutically acceptable salt" refers to salts that are not biologically or otherwise undesirable. Pharmaceutically acceptable salts include acid and base addition salts.

The term "pharmaceutically acceptable acid addition salts" refers to pharmaceutically acceptable salts formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, carbonic acid, phosphoric acid, and organic acids selected from the group consisting of aliphatic, alicyclic, aromatic, araliphatic, heterocyclic, carboxylic and sulfonic types of organic acids such as formic acid, acetic acid, propionic acid, glycolic acid, gluconic acid, lactic acid, pyruvic acid, oxalic acid, malic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, aspartic acid, ascorbic acid, glutamic acid, anthranilic acid, benzoic acid, cinnamic acid, mandelic acid, pamoic acid, phenylacetic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, and salicylic acid.

The term "pharmaceutically acceptable base addition salts" refers to those pharmaceutically acceptable salts formed with organic or inorganic bases. Examples of useful inorganic bases include sodium, potassium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, and aluminum salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-diethylaminoethanol, trimethylamine, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, methylglucamine, theobromine, purine, piperazine, piperidine, N-ethylpiperidine and polyamine resins.

The stereochemical definitions and conventions used herein generally follow the general definitions of S.P. Parker, Ed., McGraw-Hilldictionary of Chemical Terms (McGraw-Hill Chemical terminology dictionary) (1984) McGraw-Hill Book company, New York; and Eliel, E.and Wilen, S., "stereospecificity of Organic Compounds", John Wiley & Sons, Inc., New York, 1994. In describing compounds having optical activity, the prefixes D and L or R and S are used to indicate the absolute configuration of a molecule with respect to its chiral center. Substituents attached to the chiral center under study were ordered according to Cahn, Ingold, and Prelog order rules. (Cahn et al, Angew.chem.Inter.Edit.1966,5,385; reconnaissance Table 511). The prefixes D and L or (+) and (-) are used to designate the rotation index of the plane polarized light of the compound, where (-) or L indicates that the compound is levorotatory. Compounds with the prefix (+) or D are dextrorotatory.

The term "chiral center" refers to a carbon atom bound to four non-identical substituents. The term "chiral" refers to embodiments that do not overlap with a mirror image, while the term "achiral" refers to embodiments that overlap with a mirror image. Chiral molecules are optically active, i.e., they are capable of rotating the plane of plane polarized light.

The compounds of the invention may have one or more chiral centers and may exist in the form of optically pure enantiomers, mixtures of enantiomers such as, for example, racemates, optically pure diastereomers, mixtures of diastereomers, diastereomeric racemates or mixtures of diastereomeric racemates. When a chiral center is present in a chemical structure, it is intended that the present invention includes all stereoisomers associated with the chiral center.

The terms "halo", "halogen" and "halide" are used interchangeably herein and refer to fluorine, chlorine, bromine or iodine. A specific example of halogen is fluorine.

The term "alkyl" denotes a monovalent straight or branched chain saturated hydrocarbon group of 1 to 12 carbon atoms. In particular embodiments, the alkyl group has from 1 to 7 carbon atoms, and in more particular embodiments from 1 to 4 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl. Particular examples of alkyl groups are methyl and ethyl.

The term "haloalkyl" denotes an alkyl group wherein at least one hydrogen atom of the alkyl group has been replaced by the same or different halogen atoms, in particular fluorine atoms. Examples of haloalkyl include mono-, difluoro-or trifluoro-methyl, -ethyl or-propyl, such as 3,3, 3-trifluoropropyl, 2-fluoroethyl, 2,2, 2-trifluoroethyl, fluoromethyl or trifluoromethyl and the like. The term "perhaloalkyl" denotes an alkyl group wherein all of the hydrogen atoms of the alkyl group have been replaced by the same or different halogen atoms.

The term "bicyclic ring system" denotes two rings fused to each other via a common single or double bond (cyclic (linked) bicyclic ring system), via a sequence of three or more common atoms (bridged bicyclic ring system) or via a single common atom (spirobicyclic ring system). Bicyclic ring systems may be saturated, partially unsaturated, unsaturated or aromatic. The bicyclic ring system may comprise a heteroatom selected from N, O and S.

The term "cycloalkyl" refers to a saturated monocyclic or bicyclic hydrocarbon group having 3 to 10 ring carbon atoms. In a particular embodiment, cycloalkyl refers to a monovalent saturated monocyclic hydrocarbon group having 3 to 8 ring carbon atoms. Bicyclic means consisting of two saturated carbocyclic rings sharing one or more carbon atoms. Particular cycloalkyl groups are monocyclic. Examples of monocyclic cycloalkyl are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl. Examples of bicyclic cycloalkyl are bicyclo [2.2.1] heptyl or bicyclo [2.2.2] octyl. A particular example of a cycloalkyl group is cyclopropyl.

The term "heterocycloalkyl" denotes a saturated or partially unsaturated monocyclic, bicyclic or tricyclic ring system of 3 to 9 ring atoms, comprising 1,2 or 3 ring heteroatoms selected from N, O and S, the remaining ring atoms being carbon. In particular embodiments, heterocycloalkyl is a monovalent saturated monocyclic ring system of 4 to 7 ring atoms, containing 1,2 or 3 ring heteroatoms selected from N, O and S, the remaining ring atoms being carbon. Examples of monocyclic saturated heterocycloalkyl groups are aziridinyl, oxetanyl, azetidinyl, oxetanyl, pyrrolidinyl, tetrahydrofuranyl, tetrahydro-thienyl, pyrazolidinyl, imidazolidinyl, and,Oxazolidinyl, isoOxazolidinyl, thiazolidinyl, piperidinyl, tetrahydropyranyl, tetrahydrothiopyranyl, piperazinyl, morpholinyl, thiomorpholinyl, 1-dioxo-thiomorpholin-4-yl, azepinyl, diazepanyl, homopiperazinyl, or oxazepinyl. Examples of bicyclic saturated heterocycloalkyl are 8-aza-bicyclo [3.2.1]Octyl, quinuclidinyl, 8-oxa-3-aza-bicyclo [3.2.1]Octyl, 9-aza-bicyclo [3.3.1]Nonyl, 3-oxa-9-aza-bicyclo [3.3.1]Nonyl or 3-thia-9-aza-bicyclo [3.3.1]Nonyl radical. Examples of partially unsaturated heterocycloalkyl radicals are dihydrofuranyl, imidazolinyl, dihydro-Oxazolyl, tetrahydro-pyridyl or dihydropyranyl. A particular example of heterocycloalkyl is 1, 4-diazacycloHeptyl, hexahydropyrrolo [1,2-a ] groups]Pyrazinyl, piperidinyl, piperazinyl, and pyrrolidinyl. A more specific example of a heterocycloalkyl group is hexahydropyrrolo [1,2-a ]]Pyrazinyl and piperazinyl.

The term "N-heterocycloalkyl" refers to a heterocycloalkyl group containing at least one nitrogen ring atom, and wherein the point of attachment of the heterocycloalkyl group to the rest of the molecule is through the nitrogen ring atom. Particular examples of N-heterocycloalkyl are 1, 4-diazepanyl, hexahydropyrrolo [1,2-a ] pyrazinyl, piperidinyl, piperazinyl and pyrrolidinyl. More specific examples of N-heterocycloalkyl groups are hexahydropyrrolo [1,2-a ] pyrazinyl and piperazinyl.

The term "basicity" as referred to herein for compounds is expressed as the decimal logarithm of the acidity constant of the negative conjugate acid (pKa-log Ka). The larger the pKa of the conjugate acid, the stronger the base (pKa + pKb — 14). In the present application, an atom or functional group is designated as "basic" if it is suitable for accepting a proton and if the calculated pKa of its conjugate acid is at least 7, more particularly if the calculated pKa of its conjugate acid is at least 7.8, most particularly if the calculated pKa of its conjugate acid is at least 8. pKa values were calculated in silico, as described in F.Milletti et al, J.chem.Inf.model (2007)47: 2172-2181.

The term "alkylene" denotes a straight chain saturated divalent hydrocarbon group of 1 to 7 carbon atoms or a divalent branched saturated hydrocarbon group of 3 to 7 carbon atoms. Examples of alkylene groups include methylene, ethylene, propylene, 2-methylpropylene, butylene, 2-ethylbutylene, pentylene, hexylene. Specific examples of alkylene are ethylene, propylene and butylene.

The term "amino" refers to a group of the formula-NR 'R ", wherein R' and R" are independently hydrogen, alkyl, alkoxy, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, or as described herein. Alternatively, R' and R "together with the nitrogen to which they are attached may form a heterocycloalkyl group. The term "primary amino" refers to a group wherein both R' and R "are hydrogen. The term "secondary amino" refers to a group wherein R' is hydrogen and R "is a group other than hydrogen. The term "tertiary amino" refers to a group wherein neither R' nor R "is hydrogen. Particular secondary and tertiary amines are methylamine, ethylamine, propylamine, isopropylamine, aniline, benzylamine dimethylamine, diethylamine, dipropylamine and diisopropylamine.

The term "active pharmaceutical ingredient" (or "API") denotes a compound or molecule of particular biological activity in a pharmaceutical composition.

The terms "pharmaceutical composition" and "pharmaceutical formulation" (or "formulation") are used interchangeably and refer to a mixture or solution comprising a therapeutically effective amount of an active pharmaceutical ingredient and a pharmaceutically acceptable excipient that is administered to a mammal (e.g., a human) in need thereof.

The term "pharmaceutically acceptable" refers to the properties of materials that are useful in preparing pharmaceutical compositions, i.e., are generally safe, non-toxic, and not biologically or otherwise undesirable, and are useful for veterinary as well as human pharmaceutical uses.

The terms "pharmaceutically acceptable excipient", "pharmaceutically acceptable carrier" and "therapeutically inert excipient" are used interchangeably and refer to any pharmaceutical ingredient in a pharmaceutical composition that is not therapeutically active and is non-toxic to the subject to which it is administered, such as disintegrants, binders, fillers, solvents, buffers, tonicity agents, stabilizers, antioxidants, surfactants, carriers, diluents or lubricants used in formulating pharmaceutical products.

The term "individual" or "subject" refers to a mammal. Mammals include, but are not limited to, domesticated animals (e.g., cows, sheep, cats, dogs, and horses), primates (e.g., human and non-human primates such as monkeys), rabbits, and rodents (e.g., mice and rats). In certain embodiments, the individual or subject is a human.

The term "therapeutically effective amount" refers to an amount of a compound or molecule of the invention that, when administered to a subject, (i) treats or prevents a particular disease, condition, or disorder, (ii) attenuates, ameliorates, or eliminates one or more symptoms of a particular disease, condition, or disorder, or (iii) prevents or delays the onset of one or more symptoms of a particular disease, condition, or disorder described herein. The therapeutically effective amount will vary depending upon the compound, the disease state being treated, the severity of the disease being treated, the age and relative health of the subject, the route and form of administration, the judgment of the attending physician or veterinarian, and other factors.

The term "treating" of a disease state includes inhibiting the disease state, i.e., arresting the development of the disease state or its clinical symptoms, or alleviating the disease state, i.e., causing temporary or permanent regression of the disease state or its clinical symptoms.

The term "spinal muscular atrophy" (or SMA) refers to a disease caused by an inactivating mutation or deletion of the SMN1 gene on two chromosomes, resulting in loss of function of the SMN1 gene.

Symptoms of SMA include muscle weakness, low muscle tone, crying weakness, inability to cough, a tendency to lame or fall, difficulty sucking or swallowing, dyspnea, secretion accumulation in the lungs or throat, clenched fist and sweaty hands, tongue tremor/vibration, often prone head on one side (even when lying down), leg tendency weaker than the arm, leg often in the "frog leg" position, difficulty eating, increased sensitivity to respiratory infections, intestinal/bladder weakness, less than normal body weight, inability to sit unsupported, inability to walk, inability to crawl, and hypotonia, loss of reflexes, and multiple congenital contractures (joint contractures) associated with loss of anterior hom cells.

The term "treating Spinal Muscular Atrophy (SMA)" or "treatment of Spinal Muscular Atrophy (SMA)" includes one or more of the following effects: (i) reducing or improving the severity of SMA; (ii) delaying the onset of SMA; (iii) inhibiting the progression of SMA; (iv) reducing subject admission; (v) reducing the hospitalization duration of the subject; (vi) increasing survival of the subject; (vii) improving the quality of life of the subject; (viii) reducing the number of SMA-associated symptoms; (ix) reducing or ameliorating the severity of one or more symptoms associated with SMA; (x) Shortening the duration of symptoms associated with SMA; (xi) Preventing recurrence of symptoms associated with SMA; (xii) Inhibiting the development or onset of SMA symptoms; and/or (xiii) inhibiting the progression of symptoms associated with SMA.

More particularly, the term "treating SMA" means one or more of the following beneficial effects: (i) reducing muscle strength impairment; (ii) increasing muscle strength; (iii) reduction of muscle atrophy; (iv) reducing loss of motor function; (v) (ii) increase motor neurons; (vii) reducing motor neuron loss; (viii) protecting SMN-deficient motor neurons from degeneration; (ix) the motion function is improved; (x) Improving lung function; and/or (xi) reduce loss of lung function.

In more detail, the term "treatment SMA" refers to the functional capability or maintenance of said functional capability of a human infant or human toddler without assisted sitting or of a human infant, human toddler, human child or human adult without assisted standing, without assisted walking, without assisted running, without assisted breathing, without assisted turning during sleep or without assisted swallowing.

The term "EC that produces full-length SMN2 minigene mRNA_1.5xConcentration "(or" EC)_1.5xMinigene ") was defined as the concentration of test compound that effectively increased the amount of full-length SMN2 minigene mRNA to a 1.5-fold level compared to that in vector-treated cells.

The term "SMN protein expressed EC_1.5xConcentration "(or" EC)_1.5xSMN protein ") was defined as the concentration of test compound that was effective to produce 1.5 times the amount of SMN protein in the fibroblasts of SMA patients compared to the amount produced by the vehicle control.

In particular, the invention relates to compounds of formula (I)

Wherein

R¹Is hydrogen or C_1-7-an alkyl group;

R²is hydrogen, cyano, C_1-7Alkyl radical, C_1-7-haloalkyl or C_3-8-a cycloalkyl group;

R³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

a is N-heterocycloalkyl or NR¹²R¹³Wherein N-heterocycloalkyl contains 1 or 2 nitrogen ring atoms and is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹²is heterocycloalkyl containing 1 nitrogen ring atom, wherein heterocycloalkyl is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

R¹⁴independently selected from hydrogen, C_1-7Alkyl, amino-C_1-7Alkyl radical, C_3-8Cycloalkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group;

provided that if A is an N-heterocycloalkyl radical containing only 1 nitrogen ring atom, then at least one R¹⁴The substituent being amino or amino-C_1-7-an alkyl group;

and pharmaceutically acceptable salts thereof.

Particular embodiments of the present invention are compounds of formula (I) and pharmaceutically acceptable salts thereof.

Further, it is understood that references as disclosed herein relate to specific A, R¹、R²Or R³May be combined with the disclosure herein directed to additional A, R¹、R²Or R³In combination with any of the other embodiments of (1).

A particular embodiment of the present invention relates to compounds of the formula (I), in which

R¹Is hydrogen or C_1-7-an alkyl group;

R²is hydrogen, cyano, C_1-7Alkyl radical, C_1-7-haloalkyl or C_3-8-a cycloalkyl group;

R³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

a is N-heterocycloalkyl containing 1 or 2 nitrogen ring atoms, wherein N-heterocycloalkyl is optionally substituted with 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹⁴independently selected from hydrogen, C_1-7Alkyl, amino-C_1-7Alkyl radical, C_3-8Cycloalkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group;

provided that if A is an N-heterocycloalkyl radical containing only 1 nitrogen ring atom, then at least one R¹⁴The substituent being amino or amino-C_1-7-an alkyl group;

and pharmaceutically acceptable salts thereof.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R¹Is C_1-7Alkyl, in particular methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R²Is hydrogen or C_1-7Alkyl, in particular hydrogen or methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R³Is hydrogen or C_1-7Alkyl, in particular hydrogen or methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R¹²Is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Piperidinyl substituted with the substituent of (1).

A particular embodiment of the present invention relates to compounds of formula (I), wherein R¹³Is hydrogen or C_1-7Alkyl, in particular hydrogen or methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R¹⁴Independently selected from C_1-7Alkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R¹⁴Independently selected from methyl, ethyl and pyrrolidinyl or two R¹⁴Together form an ethylene group.

A particular embodiment of the invention relates to compounds of formula (I) wherein A is a saturated monocyclic or bicyclic N-heterocycloalkyl containing 1 or 2 nitrogen atoms and optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Is substituted with the substituent(s).

A particular embodiment of the invention relates to compounds of formula (I) wherein N-heterocycloalkyl or R in A is as defined herein¹²Wherein the heterocycloalkyl group is substituted by 1 or 2 groups selected from R¹⁴Is substituted with the substituent(s).

A particular embodiment of the invention relates to compounds of formula (I) wherein the N-heterocycloalkyl group in a as defined herein is further characterized in that one ring nitrogen atom is basic.

A particular embodiment of the invention relates to compounds of the formula (I) in which A isWherein

X is N or CH;

R⁴is hydrogen, C_1-7-alkyl or- (CH)₂)_m-NR⁹R¹⁰；

R⁵Is hydrogen or C_1-7-an alkyl group;

R⁶is hydrogen or C_1-7-an alkyl group;

R⁷is hydrogen or C_1-7-an alkyl group;

R⁸is hydrogen or C_1-7-an alkyl group;

R⁹and R¹⁰Independently selected from hydrogen, C_1-7-alkyl and C_3-8-a cycloalkyl group;

R¹³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

n is 0, 1 or 2;

m is 0, 1,2 or 3;

or R⁴And R⁵Together form C_1-7-an alkylene group;

or R⁴And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁶Together form C_2-7-an alkylene group;

or R⁵And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁹Together form C_1-7-an alkylene group;

or R⁷And R⁸Together form C_2-7-an alkylene group;

or R⁷And R⁹Together form C_1-7-an alkylene group;

or R⁹And R¹⁰Together form C_2-7-an alkylene group;

provided that if X is CH, then R⁴Is- (CH)₂)_m-NR⁹R¹⁰(ii) a And is

Provided that if X is N and R is⁴Is- (CH)₂)_m-NR⁹R¹⁰And m is 2 or 3.

A particular embodiment of the invention relates to compounds of the formula (I) in which A isWherein

X is N or CH;

R⁴is hydrogen, C_1-7-alkyl or- (CH)₂)_m-NR⁹R¹⁰；

R⁵Is hydrogen or C_1-7-an alkyl group;

R⁶is hydrogen or C_1-7-an alkyl group;

R⁷is hydrogen or C_1-7-an alkyl group;

R⁸is hydrogen or C_1-7-an alkyl group;

R⁹and R¹⁰Independently selected from hydrogen, C_1-7-alkyl and C_3-8-a cycloalkyl group;

n is 0, 1 or 2;

m is 0, 1,2 or 3;

or R⁴And R⁵Together form C_1-7-an alkylene group;

or R⁴And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁶Together form C_2-7-an alkylene group;

or R⁵And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁹Together form C_1-7-an alkylene group;

or R⁷And R⁸Together form C_2-7-an alkylene group;

or R⁷And R⁹Together form C_1-7-an alkylene group;

or R⁹And R¹⁰Together form C_2-7-an alkylene group;

provided that if X is CH, then R⁴Is- (CH)₂)_m-NR⁹R¹⁰(ii) a And is

Provided that if X is N and R is⁴Is- (CH)₂)_m-NR⁹R¹⁰And m is 2 or 3.

It has been found that when R is⁴、R⁵、R⁶、R⁷And R⁸When at least one of them is not hydrogen, brain penetration is enhanced.

In a particular embodiment of the invention, R⁴、R⁵、R⁶、R⁷And R⁸Is not hydrogen.

A particular embodiment of the invention relates to compounds of formula (I) wherein X is N.

A particular embodiment of the invention relates to compounds of formula (I) wherein n is 1.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁴Is hydrogen, methyl or- (CH)₂)_m-NR⁹R¹⁰And more particularly hydrogen.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁵Is hydrogen, methyl or ethyl, more particularly methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁶Is hydrogen or methyl, more particularly hydrogen.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁷Is hydrogen or methyl.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁸Is hydrogen.

A particular embodiment of the invention relates to compounds of formula (I) wherein m is 0.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁴And R⁵Together form a propylene group.

A particular embodiment of the present invention relates to compounds of formula (I), wherein R⁵And R⁶Together form an ethylene group;

a particular embodiment of the present invention relates to compounds of formula (I), wherein R⁹And R¹⁰Together form butylene groups.

A particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of:

wherein R is⁴、R⁵、R⁶、R⁷、R⁸And R¹³Is as defined herein and wherein R¹¹Is hydrogen or C_1-7-an alkyl group.

A particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of:

wherein R is⁴、R⁵、R⁶、R⁷And R⁸Is as followsAs defined herein and wherein R¹¹Is hydrogen or C_1-7-an alkyl group.

A particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of: piperazinyl, diazepanyl, pyrrolidinyl, and hexahydropyrrolo [1,2-a ]]Pyrazinyl, each of which is optionally substituted with 1,2, 3 or 4R groups as defined herein¹⁴Is substituted with the substituent(s).

A particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of: piperazin-1-yl, 1, 4-diazepan-1-yl, pyrrolidin-1-yl and hexahydropyrrolo [1,2-a ]]Pyrazin-2 (1H) -yl, each of which is optionally substituted by 1 or 2R groups as defined herein¹⁴Is substituted with the substituent(s).

A particular embodiment of the invention relates to compounds of the formula (I) in which A is NR¹²R¹³Wherein R is¹²And R¹³As defined herein.

A particular embodiment of the invention relates to compounds of the formula (I) in which A isWherein R is⁴、R⁵、R⁶、R⁷、R⁸And R¹³As defined herein.

A particular embodiment of the invention relates to compounds of the formula (I) in which A isWherein R is¹³Is hydrogen or methyl.

A particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of:

a particular embodiment of the present invention relates to compounds of formula (I) wherein a is selected from the group consisting of:

a particular embodiment of the present invention relates to compounds of formula (I), wherein R¹Is methyl, R²Is hydrogen or methyl, R³Is hydrogen and A is

Particular compounds of formula (I) of the present invention are those selected from the group consisting of:

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- (4-methylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5R) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (1, 4-diazepan-1-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (1, 4-diazepan-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (3, 3-dimethylpiperazin-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R) -3-ethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

and pharmaceutically acceptable salts thereof.

Particular compounds of formula (I) of the present invention are those selected from the group consisting of:

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5R) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

and pharmaceutically acceptable salts thereof.

The compounds of formula (VI) are suitable as intermediates for the preparation of the compounds of formula (I).

Another embodiment of the invention relates to compounds of the formula (VI)

Wherein R is¹、R²And R³Is as defined herein;

y is halogen or triflate;

and salts thereof.

A particular embodiment of the invention relates to compounds of formula (VI) wherein Y is fluorine, chlorine, bromine, iodine or triflate, in particular fluorine.

Particular compounds of formula (VI) of the present invention are those selected from the group consisting of:

7-fluoro-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-pyrido [1,2-a ] pyrimidin-4-one;

7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

and salts thereof.

Preparation method

The compounds of formula (I) as defined above and pharmaceutically acceptable salts thereof may be prepared following standard procedures known in the art.

As shown in scheme 1, a commercially available amino-pyridine of formula (II) can be reacted with a malonate to provide an intermediate of formula (III), wherein Y and R³Is as defined herein and R is C_1-2-an alkyl group,in particular methyl. The compound of formula (III) is then treated with a chlorinating agent (e.g., POCl)₃Etc.) to provide a compound of formula (IV). Then in the presence of a catalyst (e.g., (1, 1' -bis (diphenylphosphino) ferrocene) dichloropalladium (II) (Pd (dppf) Cl) in a Suzuki cross-coupling reaction₂) Etc.) and a base (e.g., K)₂CO₃Etc.) with a compound of formula (V) (wherein R is¹And R²Is as defined herein and Z is B (OH)₂Or C_1-7An alkylboronic acid ester such as 4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) to provide the compound of formula (VI). Finally, reacting a compound of formula (VI) with a compound M-A:

a) in aromatic nucleophilic substitution reactions (especially if Y is fluorine), by heating at a temperature of 80 ℃ to 200 ℃; or

b) In the Buchwald-Hartwig amination reaction, palladium catalyst (e.g., tetrakis (triphenylphosphine) palladium (Pd (PPh)) is present₃)₄) Or bis (dibenzylideneacetone) palladium (Pd (dba)₂) By heating at a temperature of from 20 ℃ to 100 ℃;

in a solvent, for example dimethyl sulfoxide (DMSO), N-methylpyrrolidinone (NMP) or Dimethylformamide (DMF), to provide a compound of formula (I) wherein a is as defined herein, M is hydrogen, sodium or potassium, especially hydrogen, and wherein M is linked to a via the nitrogen atom of a.

Scheme 1.

In one embodiment, the present invention relates to a process for the preparation of a compound of formula (I) as defined above, and pharmaceutically acceptable salts thereof, said process comprising reacting a compound of formula (VI) with a compound M-a in:

a) in aromatic nucleophilic substitution reactions (especially if Y is fluorine), by heating at a temperature of 80 ℃ to 200 ℃; or

b) In the Buchwald-Hartwig amination reaction, palladium catalyst (e.g., tetrakis (triphenylphosphine) palladium (Pd (PPh)) is present₃)₄) Or bis (dibenzylideneacetone) palladium (Pd (dba)₂) By heating at a temperature of from 20 ℃ to 100 ℃;

reaction in a solvent, such as dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or Dimethylformamide (DMF), wherein A, Y, R¹、R²And R³Is as defined herein, M is hydrogen, sodium or potassium, in particular hydrogen, and wherein M is linked to a via the nitrogen atom of a.

A particular embodiment of the present invention relates to a process for the preparation of a compound of formula (I) as defined above and pharmaceutically acceptable salts thereof, said process comprising an aromatic nucleophilic substitution reaction between a compound of formula (VI) as defined above and a compound of formula M-A by heating in a solvent, wherein A, R¹、R²、R³And Y is as defined above, M is hydrogen, sodium or potassium, and wherein M is linked to a via the nitrogen atom of a.

A particular embodiment of the present invention relates to a process for the preparation of compounds of formula (I) as defined above and pharmaceutically acceptable salts thereof, wherein the aromatic nucleophilic substitution reaction is carried out at a temperature of 80 ℃ to 200 ℃.

A particular embodiment of the present invention relates to a process for the preparation of compounds of formula (I) as defined above and pharmaceutically acceptable salts thereof, wherein the solvent of the aromatic nucleophilic substitution reaction is selected from the group consisting of dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) and Dimethylformamide (DMF).

A particular embodiment of the present invention relates to a process for the preparation of compounds of formula (I) as defined above, wherein M is hydrogen, and pharmaceutically acceptable salts thereof.

In particular, compounds of formula (I) and pharmaceutically acceptable salts thereof may be prepared according to the methods described in the examples herein.

Pharmaceutical composition

Another embodiment provides pharmaceutical compositions or medicaments comprising a compound of the invention and a therapeutically inert carrier, diluent or pharmaceutically acceptable excipient, and methods of using the compounds of the invention to prepare such compositions and medicaments.

The compositions are formulated, dosed and administered in a manner consistent with good medical practice. Factors to be considered in this regard include the particular condition being treated, the particular mammal being treated, the clinical condition of the individual patient, the cause, the site of drug delivery, the method of administration, the timing of administration, and other factors known to the practitioner.

The compounds of the invention may be administered by any suitable means including oral, topical (including buccal and sublingual), rectal, vaginal, transdermal, parenteral, subcutaneous, intraperitoneal, intrapulmonary, intradermal, intrathecal and epidural and intranasal and, if desired for topical treatment, intralesional administration. Parenteral injection includes intramuscular, intravenous, intraarterial, intraperitoneal or subcutaneous administration.

The compounds of the present invention may be administered in any convenient form of administration, such as, for example, tablets, powders, capsules, solutions, dispersions, suspensions, syrups, sprays, suppositories, gels, emulsions, patches and the like. Such compositions may contain conventional ingredients of pharmaceutical preparations such as diluents, carriers, pH adjusting agents, preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavors, salts for varying the osmotic pressure, buffers, masking agents, antioxidants and other active agents. It may also contain other therapeutically valuable substances.

Typical formulations are prepared by mixing a compound of the invention with a carrier or excipient. Suitable carriers and excipients are known to those skilled in the art and are described in detail, for example, in Ansel h.c. et al, Ansel's pharmaceutical Dosage Forms and Drug Delivery Systems (Ansel pharmaceutical Dosage Forms and Drug Delivery Systems) (2004) Lippincott, Williams & Wilkins, philiadelphia; gennaro A.R. et al, Remington: The Science and Practice of Pharmacy (Remington: pharmaceutical sciences and practices) (2000) Lippincott, Williams & Wilkins, Philadelphia; and Rowe R.C, Handbook of Pharmaceutical Excipients (2005) Pharmaceutical Press, Chicago. The formulations may also contain one or more buffering agents, stabilizing agents, surfactants, wetting agents, lubricating agents, emulsifying agents, suspending agents, preservatives, antioxidants, opacifiers, glidants, processing aids, colorants, sweeteners, flavoring agents, diluents and other known additives to provide an elegant appearance of the drug (i.e., a compound of the present invention or a pharmaceutical composition thereof) or to aid in the manufacture of the pharmaceutical product (i.e., a pharmaceutical product).

The administrable dose of the compounds of the invention can vary widely and will of course be adapted to the individual needs in each particular case. In general, in the case of oral administration, a daily dose of about 0.01 to 1000mg per person of a compound of the formula (I) should be appropriate, but the above upper limit can also be exceeded when desired.

An example of a suitable oral dosage form is a tablet containing about 100mg to 500mg of a compound of the invention complexed with about 30 to 90mg of anhydrous lactose, about 5 to 40mg of croscarmellose sodium, about 5 to 30mg polyvinylpyrrolidone (PVP) K30 and about 1 to 10mg of magnesium stearate. The powder ingredients are first mixed together and then mixed with a solution of PVP. The resulting composition may be dried, granulated, mixed with magnesium stearate and compressed into tablet form using conventional equipment.

An example of an aerosol formulation can be prepared by: for example, 10 to 100mg of a compound of the invention is dissolved in a suitable buffer solution (e.g. phosphate buffer) and if necessary a tonicity modifier, for example a salt such as sodium chloride, is added. The solution may be filtered to remove impurities and contaminants, for example, using a 0.2 μm filter.

Use of

As mentioned above, the compounds of formula (I) and pharmaceutically acceptable salts thereof have valuable pharmacological properties and have been found to enhance the inclusion of exon 7 of SMN1 and/or SMN2 into mRNA transcribed from the SMN1 and/or SMN2 gene, thereby increasing expression of the SMN protein in a human subject in need thereof.

The compounds of the invention may be used, alone or in combination with other drugs, for the treatment or prevention of diseases caused by inactivating mutations or deletions in the SMN1 gene and/or associated with loss or defect of function of the SMN1 gene. These diseases include, but are not limited to, Spinal Muscular Atrophy (SMA).

A particular embodiment of the present invention relates to a pharmaceutical composition comprising a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof as defined above and one or more pharmaceutically acceptable excipients.

A particular embodiment of the present invention relates to a pharmaceutical composition comprising a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof and one or more pharmaceutically acceptable excipients for the treatment or prevention of a disease caused by an inactivating mutation or deletion of the SMN1 gene and/or associated with a loss or defect of function of the SMN1 gene, in particular for the treatment or prevention of SMA.

A particular embodiment of the present invention relates to compounds of formula (I) as defined above or pharmaceutically acceptable salts thereof for use as therapeutically active substances, in particular for use as therapeutically active substances for the treatment or prevention of diseases which are caused by an inactivating mutation or deletion of the SMN1 gene and/or which are associated with a loss or defect of function of the SMN1 gene, in particular for the treatment or prevention of Spinal Muscular Atrophy (SMA).

A particular embodiment of the present invention relates to compounds of formula (I) as defined above or pharmaceutically acceptable salts thereof for use in the treatment or prevention of diseases caused by an inactivating mutation or deletion of the SMN1 gene and/or associated with a loss or defect of SMN1 gene function, in particular for use in the treatment or prevention of Spinal Muscular Atrophy (SMA).

A particular embodiment of the present invention relates to a method for the treatment or prevention of a disease caused by an inactivating mutation or deletion of the SMN1 gene and/or associated with a loss or defect of function of the SMN1 gene, in particular for the treatment or prevention of Spinal Muscular Atrophy (SMA), which comprises administering to a subject a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof.

A particular embodiment of the invention relates to the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof as defined above for the treatment or prevention of a disease caused by an inactivating mutation or deletion of the SMN1 gene and/or associated with a loss or defect of SMN1 gene function, in particular for the treatment or prevention of Spinal Muscular Atrophy (SMA).

A particular embodiment of the present invention relates to the use of a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof for the preparation of a medicament for the treatment or prevention of a disease caused by an inactivating mutation or deletion of the SMN1 gene and/or associated with a loss or defect of function of the SMN1 gene, in particular for the treatment or prevention of Spinal Muscular Atrophy (SMA). Such medicaments comprise a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof.

Examples

The invention will be more fully understood by reference to the following examples. The following examples, however, should not be construed as limiting the scope of the invention.

Abbreviations used

ACN: acetonitrile; CH (CH)₂Cl₂: dichloromethane (DCM); DIPEA: diisopropylethylamine; DMA: dimethylacetamide; TEA: triethylamine; RT: room temperature; b is₂(pin)₂: bis (pinacol) diboron; pd (dp)pf)Cl₂: (1, 1' -bis (diphenylphosphino) ferrocene) dichloropalladium (II); PPTS: pyridine p-toluenesulfonate

Intermediate 1

7-fluoro-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

a) 2-chloro-7-fluoro-pyrido [1,2-a]Pyrimidin-4-ones

A mixture of 2-amino-5-fluoropyridine (11.20g, 0.10mol) and dimethyl malonate (57.0mL, 0.50mol) was heated at 230 ℃ for 1.5 h. After cooling to room temperature, the precipitate was filtered and washed with ACN (3 ×) to afford 7-fluoro-2-hydroxy-4H-pyrido [1,2-a]Pyrimidin-4-one, as a dark solid (14g), was used directly in the next step. MS M/z181.3[ M + H ]]⁺。

Crude 7-fluoro-2-hydroxy-4H-pyrido [1,2-a ] is reacted with a solvent to form a mixture]Pyrimidin-4-one (14g, 77mmol) in POCl₃A dark mixture in DIPEA (13.3mL, 77mmol) and (50mL) was heated at 110 ℃ for 15 h. The solvent was removed and the dark residue was treated with ice water, washed with water (3 ×) and dried to afford a brown solid. The crude brown solid was chromatographed (5% MeOH in CH)₂Cl₂To provide 2-chloro-7-fluoro-4H-pyrido [1,2-a ]]Pyrimidin-4-one as a yellow solid (9.84g, 50%, 2 steps), MS M/z 199.2[ M + H ]]⁺。

b) 2-methyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b] Pyridazine

Reacting 6-chloro-2-methylimidazo [1,2-b ]]Pyridazine (900mg, 5.37mmol), 4,4,4 ', 4 ', 5,5 ', 5 ' -octamethyl-2, 2 ' -bis (1,3, 2-dioxaborolane) (1.36g, 5.37mmol, 1.0 equiv.), KOAc (1.05g, 10.7mmol) and Pd (dppf) Cl₂·CH₂Cl₂(393mg, 0.54mmol) in twoThe mixture in alkane (50mL) was degassed and in N₂Heating was carried out at 95 ℃. After 15 hours, the mixture was diluted with EtOAc, filtered through celite and concentrated in vacuo to afford 2-methyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine, which was used directly in the next step.

c) 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-ones

To 2-chloro-7-fluoro-4H-pyrido [1,2-a ]]A solution of pyrimidin-4-one (750mg, 3.78mmol) in ACN (36mL) was added 2-methyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine (1.17g, 4.53mmol, eq: 1.2), Pd (Ph)₃P)₄(218mg, 0.189mmol, 0.05 equiv.) and K₂CO₃Aqueous solution of (3.78mL, 7.55mmol, 2.0 equiv.). The mixture was degassed and heated at 105 ℃ under argon overnight. The reaction was cooled to RT and filtered. The precipitate was washed with Et₂O washes then water washes, dried in vacuo to afford 250mg (22%) of 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one as a light brown solid. MS M/z296.1[ M + H ]]⁺。

Intermediate 2

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-pyrido [1,2-a ] pyrimidin-4-one

a)2, 8-dimethyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1, 2-b]pyridazine

In a sealed flask, 3, 6-dichloro-4-methylpyridazine (27g, 161mmol) was suspended in aqueous ammonia (25%, 300 mL). The reaction mixture was heated at 110 ℃ for 48 hours (to become a solution after 1 hour). After cooling to room temperature, the reaction was poured into CH₂Cl₂And separating the organic phase with Na₂SO₄Dried and concentrated in vacuo to afford 22.4g of 6-chloro-4-methyl-pyridazin-3-amine and 6-chloro-5-methyl-pyridazin-3-amine as a mixture of regioisomers, which was used directly in the next step.

A mixture of regioisomers 6-chloro-4-methyl-pyridazin-3-amine and 6-chloro-5-methyl-pyridazin-3-amine (22.4g) was suspended in 2-propanol (300 mL). 1-bromo-2, 2-dimethoxypropane (36.0g, 26.6mL, 193mmol, 1.2 equiv.) and PPTS (2.96g, 11.6mmol, 0.0725 equiv.) were added and the resulting solution was heated at 105 ℃ overnight. The solvent was removed in vacuo and the residue taken up in CH₂Cl₂NaHCO is used for neutralization₃And (6) washing. The organic phase is treated with Na₂SO₄Dried, concentrated in vacuo and the crude light brown solid was chromatographed (EtOAc/heptane 1/2-1/1) to afford separately 6.1g of 6-chloro-2, 8-dimethyl-imidazo [1,2-b ] as a white solid]Pyridazines MS M/z 182.1[ M + H ]]⁺(21%) and 5.9g of 6-chloro-2, 7-dimethyl-imidazo [1,2-b ] as a white solid]Pyridazines MS M/z 182.1[ M + H ]]⁺(20％)。

Mixing 6-chloro-2, 8-dimethylimidazo [1,2-b ]]Pyridazine (0.9g, 4.96mmol), 4,4,4 ', 4 ', 5,5,5 ', 5 ' -octamethyl-2, 2 ' -bis (1,3, 2-dioxaborolane) (1.26g, 4.96mmol, 1.0 equiv.), KOAc (0.97g, 9.91mmol) and Pd (dppf) Cl₂·CH₂Cl₂(363mg, 0.49mmol) in bisThe mixture in alkane (50mL) was degassed and in N₂Heating was carried out at 110 ℃. After 15 h, the mixture was diluted with EtOAc, filtered through celite and concentrated in vacuo to afford 2, 8-dimethyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine, which was used directly in the next step.

b)2- (2, 8-dimethylimidazo [1, 2-b)]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-ones

To 2-chloro-7-fluoro-4H-pyrido [1,2-a ]]A solution of pyrimidin-4-one (750mg, 3.78mmol, described above) in ACN (36mL) was added 2, 8-dimethyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine (1.24g, 4.53mmol, 1.2 equiv.), Pd (Ph)₃P)₄(218mg, 0.189mmol, 0.05 equiv.) and K₂CO₃Aqueous solution of (3.78mL, 7.55mmol, 2.0 equiv.). The mixture was degassed and heated at 100 ℃ under argon for 6 hours. The reaction was cooled to RT and filtered. The precipitate was washed with Et₂O washes then water washes, dried in vacuo to afford 700mg (60%) of 2- (2, 8-dimethylimidazo [1,2-b ]]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one as a light brown solid. MS M/z 310.1[ M + H ]]⁺。

Intermediate 3

7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

a) 2-chloro-7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-ones

A mixture of 5-fluoro-3-methylpyridin-2-amine (3.3g, 26.2mmol) and dimethyl malonate (15.0mL, 0.13mol, 5.0 equiv.) was heated at 210 ℃ for 1.5 hours. After cooling to room temperature, the precipitate was filtered and washed with ACN (3 ×) to afford 7-fluoro-2-hydroxy-9-methyl-pyrido [1,2-a]Pyrimidin-4-one, as a dark solid (2.3g), was used directly in the next step. MS M/z 195.1[ M + H ]]⁺。

Mixing crude 7-fluoro-2-hydroxy-9-methyl-pyrido [1,2-a ]]Pyrimidin-4-one (2.3g, 11.8mmol) in POCl₃A mixture of (7.7mL, 82.9mmol) and DIEA (2.07mL, 11.8mmol) was heated at 110 deg.C for 15 hours. The solvent was removed and the residue was treated with ice water, washed with water (3 ×) and dried to afford a brown solid. The crude brown solid was chromatographed (5% MeOH in CH)₂Cl₂To provide 2-chloro-7-fluoro-9-methyl-pyrido [1,2-a ]]Pyrimidin-4-one as a yellow solid (1.77g, 70%, 2 steps), MS M/z 213.1[ M + H ]]⁺。

b) 7-fluoro-9-methyl-2- (2-methylimidazo [1, 2-b)]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-ones

To 2-chloro-7-fluoro-9-methyl-4H-pyrido [1,2-a ]]A solution of pyrimidin-4-one (2.2g, 10.3mmol) in ACN (80mL) was added 2-methyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine (3.22g, 12.4mmol, 1.2 equiv, described above), Pd (Ph)₃P)₄(1.20g, 1.03mmol, 0.1 eq.) and K₂CO₃Aqueous solution of (2.0 equiv., 20.7mmol, 10.3 mL). The mixture was degassed and heated at 100 ℃ under argon for 6 hours. The reaction was cooled to RT and filtered. The precipitate was washed with Et₂O washes then water washes, dried in vacuo to afford 1.80g (56%) of 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one as a light brown solid. MS m/z 310.1[M+H]⁺。

Intermediate 4

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a ] pyrimidin-4-one

To 2-chloro-7-fluoro-9-methyl-4H-pyrido [1,2-a ]]A solution of pyrimidin-4-one (0.98g, 4.61mmol, described above) in ACN (50mL) was added 2, 8-dimethyl-6- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) imidazo [1,2-b]Pyridazine (1.51g, 5.53mmol, 1.2 equiv, described above), Pd (Ph)₃P)₄(0.32g, 0.277mmol, 0.06 equiv.) and K₂CO₃Aqueous solution of (4.61mL, 9.22mmol, 2.0 equiv.). The mixture was degassed and heated at 100 ℃ under argon for 6 hours. The reaction was cooled to RT and filtered. The precipitate was washed with Et₂O and water, then dried in vacuo to afford 0.89g (60%) of 2- (2, 8-dimethylimidazo [1,2-b ]]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one as a light brown solid. MS M/z 324.4[ M + H ]]⁺。

Example 1

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- (4-methylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 35mg, 0.119mmol) and 1-methylpiperazine (47.5mg, 0.474mmol, 4 equivalents) were stirred in DMSO (1mL) at 120 ℃ overnight. LC-MS showed complete conversion. The solvent was removed under high vacuum. Will be provided withThe crude product was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 9/1) to provide the title product (25mg, 56%) as a light yellow solid. MS M/z376.3[ M + H ]⁺]。

Example 2

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 125mg, 0.426mmol) and (R) -octahydropyrrolo- [1,2-a]Pyrazine (160mg, 1.27mmol, 3 equiv.) was stirred in DMSO (5mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 95/5) to provide the title product (65mg, 38%) as a light yellow solid. MS M/z 402.5[ M + H ]⁺]。

Example 3

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1, 2]-b]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 200mg, 0.647mmol) and (S) -octahydropyrrolo- [1, 2-a)]Pyrazine (286mg, 2.26mmol, 3.5 equiv.) was stirred in DMSO (5mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 95/5) to provide the title product (115mg, 43%) as a light yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 4

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 200mg, 0.647mmol), DIPEA (0.113mL, 0.67mmol, 1 equiv.) and (R) -octahydropyrrolo- [1, 2-a)]Pyrazine (245mg, 1.95mmol, 3.0 equiv.) was stirred in DMSO (2.5mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 95/5) to provide the title product (132mg, 49%) as a light yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 5

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 90mg, 0.291mmol), DIPEA (0.05mL, 0.29mmol, 1 eq.) and (S) -8 a-methyloctahydropyrrolo [1,2-a ]]Pyrazine (81mg, 0.58mmol, 2.0 equiv.) was stirred in DMSO (2.5mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (55mg, 44%) as a light yellow solid. MS M/z 430.3[ M + H ]⁺]。

Example 6

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 90mg, 0.291mmol), DIPEA (0.05mL, 0.29mmol, 1 eq.) and (R) -8 a-methyloctahydropyrrolo [1,2-a ]]Pyrazine (81mg, 0.58mmol, 2.0 equiv.) was stirred in DMSO (2.5mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (50mg, 40%) as a light yellow solid. MS M/z 430.4[ M + H ]⁺]。

Example 7

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5R) -3, 5-Dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 50mg, 0.162mmol) and cis-2, 6-dimethylpiperazine (74mg, 0.647mmol, 4.0 equiv.) were stirred in DMSO (1.5mL) at 110 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (32mg, 49%) as a light yellow solid. MS M/z 404.4[ M + H ]⁺]。

Example 8

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 33mg, 0.107mmol) and (S) -2-methylpiperazine (43mg, 0.427mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 120 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (18mg, 43%) as a light yellow solid. MSm/z 390.3[ M + H ]⁺]。

Example 9

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 85mg, 0.275mmol) and (R) -2-methylpiperazine (110mg, 1.10mmol, 4.0 equiv.) were stirred in DMSO (5mL) at 120 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (35mg, 33%) as a light yellow solid. MSm/z 390.3[ M + H ]⁺]。

Example 10

7- (1, 4-Diazepan-1-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 33mg, 0.107mmol) and 1, 4-diazepane (32mg, 0.320mmol, 3.0 equiv.) were stirred in DMSO (2mL) at 120 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (20mg, 48%) as a light yellow solid. MSm/z 390.3[ M + H ]⁺]。

Example 11

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and (S) -2-methylpiperazine (68mg, 0.677mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 110 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (40mg, 63%) as a light yellow solid. MS M/z376.2[ M + H ]⁺]。

Example 12

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and (R) -2-methylpiperazine (68mg, 0.677mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 110 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (48mg, 75%) as a light yellow solid. MS M/z376.3[ M + H ]⁺]。

Example 13

7- (1, 4-diazepan-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and 1, 4-diazepane (68mg, 0.677mmol, 4.0 equiv.) in DMSO (2mL)Stirring was carried out overnight at 110 ℃. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (41mg, 65%) as a light yellow solid. MSm/z 376.2[ M + H ]⁺]。

Example 14

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and cis-2, 6-dimethylpiperazine (77mg, 0.677mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 110 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (41mg, 62%) as a light yellow solid. MSm/z 390.3[ M + H ]⁺]。

Example 15

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and (S) -octahydropyrrolo [1,2-a ]]Pyrazine (85mg, 0.677mmol, 4.0 equiv.) was stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (36mg, 53%) as a light yellow solid. MS M/z 402.3[ M + H ]⁺]。

Example 16

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol) and (S) -8 a-methyloctahydropyrrolo [1,2-a ]]Pyrazine (95mg, 0.677mmol, 4.0 equiv.) was stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (45mg, 64%) as a light yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 17

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 100mg, 0.339mmol) and (R) -8 a-methyloctahydropyrrolo [1,2-a ]]Pyrazine (190mg, 1.35mmol, 4.0 equiv.) was stirred in DMSO (4mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (45mg, 64%) as a light yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 18

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a microwave reactor, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 45mg, 0.145mmol), (R) -1, 3' -dipyrrolidine dihydrochloride (62mg, 0.291mmol, 2.0 equiv.), and DIPEA (0.20mL, 1.16mmol, 8 equiv.) in NMP (3mL)Stirring was carried out at 220 ℃ for 1 hour. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 90/10) to provide the title product (25mg, 40%) as a light yellow solid. MS M/z 430.3[ M + H ]⁺]。

Example 19

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 50mg, 0.169mmol), DIPEA (0.24mL, 1.35mmol, 8 equiv.), and 4, 7-diazaspiro [2.5]]Octane dihydrochloride (62.7mg, 0.339mmol, 2.0 equiv.) was stirred in DMSO (2mL) at 125 ℃ for 2 days. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (22mg, 33%) as a light yellow solid. MS M/z 388.3[ M + H ]⁺]。

Example 20

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 50mg, 0.162mmol), DIPEA (0.22mL, 1.29mmol, 4 equiv.), and 4, 7-diazaspiro [2.5]]Octane dihydrochloride (32mg, 0.320mmol, 3.0 equiv.) was stirred in DMSO (2mL) at 130 ℃ for 48 hours. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 95/5) to provide the title product (12mg, 18%) as a light yellow solid. MS M/z 402.3[ M + H ]⁺]。

Example 21

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 40mg, 0.135mmol), DIPEA (0.19mL, 1.08mmol, 8 equivalents) and (R) -1, 3' -bipyrrolidine dihydrochloride (58mg, 0.271mmol, 2.0 equivalents) were stirred in DMSO (4mL) and heated in a microwave at 220 ℃ for 40 min. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 98/2 to 90/10) fromThe title product was provided (30mg, 53%) as a pale yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 22

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 40mg, 0.129mmol) and 2, 2-dimethylpiperazine (59mg, 0.517mmol, 4.0 equivalents) were stirred in DMSO (1.6mL) at 130 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 9/1) to provide the title product (29mg, 55%) as a light yellow solid. MSm/z 404.3[ M + H ]⁺]。

Example 23

7- (3, 3-dimethylpiperazin-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 40mg, 0.135mmol) and 2, 2-dimethylpiperazine (62mg, 0.542mmol, 4.0 equivalents) were stirred in DMSO (2mL) at 130 ℃ overnight. At a high levelThe solvent was removed under vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (26mg, 49%) as a light yellow solid. MS M/z390.3[ M + H ]⁺]。

Example 24

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one (intermediate 4; 50mg, 0.155mmol) and (S) -2-methylpiperazine (62mg, 0.619mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (45mg, 72%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 25

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one (intermediate 4; 50mg, 0.155mmol) and (R) -2-methylpiperazine (62mg, 0.619mmol, 4.0 equiv.) were stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (40mg, 70%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 26

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one (intermediate 4; 50mg, 0.155mmol) and cis-2, 6-dimethylpiperazine (70mg, 0.619mmol, 4.0 equivalents) were stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (26mg, 40%) as a light yellow solid. MS M/z 418.3[ M + H ]⁺]。

Example 27

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one (intermediate 4; 50mg, 0.155mmol) and 2, 2-dimethylpiperazine (35mg, 0.309mmol, 2.0 equiv.) were stirred in DMSO (2mL) at 125 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (36mg, 56%) as a light yellow solid. MS M/z 418.3[ M + H ]⁺]。

Example 28

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a]Pyrimidin-4-one (intermediate 4; 50mg, 0.155mmol), DIPEA (0.21mL, 1.24mmol, 8 equiv.), and 4, 7-diazaspiro [2.5]]Octane dihydrochloride (57mg, 0.309mmol, 2.0 equiv.) was stirred in DMSO (2mL) at 125 ℃ for 2 days. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (17mg, 26%) as a light yellow solid. MS M/z 416.3[ M + H ]⁺]。

Example 29

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5S) -3, 5-Dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 50mg, 0.162mmol), TEA (0.18mL, 1.29mmol, 8 equiv.), and (2S,6S) -2, 6-dimethylpiperazine dihydrochloride (90mg, 0.485mmol, 3.0 equiv.) were stirred in DMSO (2mL) at 140 deg.C overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 9/1) to provide the title product (20mg, 30%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 30

2- (2, 8-Dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 2- (2, 8-dimethyl imidazo [1,2-b ] is added]Pyridazin-6-yl) -7-fluoro-pyrido [1,2-a]Pyrimidin-4-one (intermediate 2; 50mg, 0.162mmol), DIPEA (0.22mL, 1.29mmol, 8 equivalents), and (S) -1, 3' -bipyrrolidine dihydrochloride (103mg, 0.485mmol, 3.0 equivalents) were stirred in NMP (2mL) at 140 deg.C overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 9/1) to provide the title product (22mg, 32%) as a light yellow solid. MS M/z 430.3[ M + H ]⁺]。

Example 31

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 75mg, 0.254mmol), TEA (0.28mL, 2.03mmol, 8 equiv.), and (S) -1, 3' -bipyrrolidine dihydrochloride (162mg, 0.762mmol, 3.0 equiv.) were stirred in NMP (4mL) and heated in a microwave at 220 ℃ for 1 hour. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (12mg, 11%) as a light yellow solid. MS M/z 416.2[ M + H ]⁺]。

Example 32

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 75mg, 0.254mmol), TEA (0.28mL, 2.03mmol, 8 equiv.), and (2S,6S) -2, 6-dimethylpiperazine dihydrochloride (143mg, 0.762mmol, 3.0 equiv.) were stirred in DMSO (3mL) and heated at 140 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (10mg, 10%) as a light yellow solid. MS M/z390.3[ M + H ]⁺]。

Example 33

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 250mg, 0.808mmol) and (S) -2-methylpiperazine (405mg, 4.04mmol, 5.0 equiv.) were stirred in DMSO (6mL) and heated at 130 deg.COvernight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 85/15) to provide the title product (135mg, 43%) as a light yellow solid. MS M/z390.3[ M + H ]⁺]。

Example 34

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 250mg, 0.808mmol) and (R) -2-methylpiperazine (405mg, 4.04mmol, 5.0 equiv.) were stirred in DMSO (6mL) and heated at 130 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 85/15) to provide the title product (100mg, 32%) as a light yellow solid. MS M/z390.3[ M + H ]⁺]。

Example 35

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 250mg, 0.808mmol) and (2S,6R) -2, 6-dimethylpiperazine (461mg, 4.04mmol, 5.0 equiv.) were stirred in DMSO (6mL) and heated at 130 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 85/15) to provide the title product (101mg, 31%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 36

7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 250mg, 0.808mmol) and 2, 2-dimethylpiperazine (461mg, 4.04mmol, 5.0 equiv.) were stirred in DMSO (6mL) and heated at 130 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 85/15) to provide the title product (120mg, 36%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 37

7- (4, 7-diazaspiro [2.5] oct-7-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 125mg, 0.404mmol), K₂CO₃(223mg, 1.62mmol, 4 equiv.) and 4, 7-diazaspiro [2.5]Octane dihydrochloride (112mg, 0.606mmol, 1.5 equiv.) was stirred in DMA (2mL) and heated at 130 deg.C overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (75mg, 46%) as a light yellow solid. MS M/z 402.2[ M + H ]⁺]。

Example 38

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, 7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) pyrido [1,2-a]Pyrimidin-4-one (intermediate 3; 125mg, 0.404mmol), K₂CO₃(223mg, 1.62mmol, 4 equiv.) and (2S,6S) -2, 6-dimethylpiperazine dihydrochloride (113 m)g, 0.606mmol, 1.5 equiv.) was stirred in DMA (2mL) and heated at 130 ℃ overnight. The solvent was removed under high vacuum. The residue is placed in CH₂Cl₂NaHCO is used for neutralization₃Is washed with a saturated aqueous solution. The organic layer was separated and Na was used₂SO₄Dried and concentrated in vacuo. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 90/10) to provide the title product (50mg, 31%) as a light yellow solid. MS M/z 404.3[ M + H ]⁺]。

Example 39

7- [ (3R) -3-ethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one

In a sealed tube, adding 7-fluoro-2- (2-methylimidazo [1,2-b ]]Pyridazin-6-yl) -4H-pyrido [1,2-a]Pyrimidin-4-one (intermediate 1; 200mg, 0.677mmol), K₂CO₃(374mg, 2.71mmol, 4 equiv.) and (R) -2-ethylpiperazine dihydrochloride (238mg, 0.606mmol, 1.5 equiv.) were stirred in DMA (3mL) at 100 ℃ for 4 days. The solvent was removed under high vacuum. The crude material was purified by column chromatography (SiO)₂，CH₂Cl₂MeOH 95/5 to 8/2) to provide the title product (168mg, 64%) as a light yellow solid. MS M/z 390.2[ M + H ]⁺]。

Biological assay

To describe this in more detail and to facilitate an understanding of the specification, the following non-limiting biological examples are provided to more fully illustrate the scope of the specification and are not to be construed as specifically limiting its scope. Such variations of the present description, now known or later developed, which would be within the purview of one skilled in the art are considered to fall within the scope of the present description and as hereinafter claimed. These examples illustrate in vitro and/or in vivo testing of certain compounds described herein and demonstrate the usefulness of the compounds to treat SMA by enhancing the inclusion of exon 7 of SMN2 in mRNA transcribed from the SMN2 gene. The compounds of formula (I) enhance inclusion of exon 7 of SMN2 in mRNA transcribed from the SMN2 gene and increase the level of SMN protein produced by the SMN2 gene, and thus may be used to treat SMA in a human subject in need thereof. These examples also illustrate in vitro and/or in vivo testing of certain compounds described herein and demonstrate the usefulness of the compounds to enhance the inclusion of exon 7 of SMNI in mRNA transcribed from the SMN1 gene. Thus, the compound of formula (I) also enhances the inclusion of exon 7 of SMN1 in mRNA transcribed from the SMN1 gene and increases the level of SMN protein produced by the SMN1 gene.

Measurement 1

SMN2 minigene mRNA splicing RT-qPCR assay in cultured cells

Reverse transcription-quantitative PCR (RT-qPCR) based assays were used to quantify the levels of full-length SMN2 minigene (referred to herein as the term "FL SMN2 mini") mRNA containing SMN2 exon 7 in HEK293H cell lines stably transfected with the minigene and treated with test compounds. The materials used and the respective sources are listed in table 1 below.

TABLE 1 materials and sources thereof used in SMN2 minigene mRNA splicing RT-qPCR assays in cultured cells.

SMN2-a minigene constructs were made as described in international patent application WO2009/151546a1, page 145, paragraph [00400] to page 147, paragraph [00412] (including figures 1 and 3 therein).

HEK293H cells (10,000 cells/well) stably transfected with SMN2-A minigene construct were seeded in 200. mu.L cell culture medium (DM) in 96-well flat bottom platesEM plus 10% FBS and 200 μ g/mL hygromycin) and the plates were immediately swirled to ensure that the cells were properly dispersed and a uniform cell monolayer was formed. Cells were allowed to attach for 6 hours. Test compounds were serially diluted 3.16-fold in 100% DMSO to generate a 7-point concentration curve. Solutions of test compounds (1 μ L, 200 ×, in DMSO) were added to each well containing cells and the plates were placed in a cell incubator (37 ℃, 5% C0)₂100% relative humidity) for 24 hours. 2 replicates were prepared for each test compound concentration. The Cells were then lysed in cell-To-Ct lysis buffer and the lysates stored at-80 ℃.

The full length SMN2-a minigene and GAPDH mRNA were quantified using the primers and probes indicated in table 2. Primer SMN forward a (SEQ ID No.1) hybridizes to a nucleotide sequence in exon 7 (nucleotides 22 to 40), primer SMN reverse a (SEQ ID No.2) hybridizes to a nucleotide sequence in the coding sequence of firefly luciferase, SMN probe a (SEQ ID No.3) hybridizes to a nucleotide sequence in: exon 7 (nucleotide 50 to nucleotide 54) and exon 8 (nucleotide 1 to nucleotide 21). The combination of these three oligonucleotides detected only the SMN1 or SMN2 minigene (RT-qPCR) and not the endogenous SMN1 or SMN2 gene.

Table 2.¹Primers and probes designed by PTC Therapeutics, inc;²commercially available from Life technologies, Inc. (formerly Invitrogen).

The SMN forward and reverse primers were used at a final concentration of 0.4 μ M. The SMN probe was used at a final concentration of 0.15 μ M. GAPDH primers were used at a final concentration of 0.2. mu.M and the probe was used at a final concentration of 0.15. mu.M.

A SMN 2-minigene GAPDH mixture (15 μ L total volume) was prepared by combining: 7.5 μ L of 2 XTT-PCR buffer, 0.4 μ L of 25 XTT-PCR enzyme mix, 0.75 μ L of 20 XGAPDH primer-probe mix, 4.0075 μ L of water, 2 μ L of 10 fold diluted cell lysate, 0.06 μ L of 100 μ M SMN forward primer, 0.06 μ L of 100 μ M SMN reverse primer, and 0.225 μ L of 100 μ M SMN probe.

PCR was performed at the following temperatures for the indicated times: step 1: 48 deg.C (15 min); step 2: 95 deg.C (10 min); and step 3: 95 ℃ (15 sec); and 4, step 4: 60 deg.C (1 min); steps 3 and 4 are then repeated for a total of 40 cycles.

Each reaction mixture contained both the SMN2-a minigene and GAPDH primer/probe set (multiplex design), allowing simultaneous measurement of the levels of both transcripts.

The increase in abundance of FL SMN2mini mRNA relative to cells treated with the vehicle control was determined from real-time PCR data using a modified Δ Δ Ct method (as described in Livak and schmitgen, Methods,2001,25: 402-8). The amplification efficiency E was calculated from the slope of the amplification curves for FL SMN2mini and GAPDH alone. Then, the abundance of FL SMN2mini and GAPDH mRNAs was calculated as (1+ E)^-CtWhere Ct is the threshold for each amplicon. FL SMN2mini mRNA abundance was normalized to GAPDH mRNA abundance. The normalized FL SMN2mini mRNA abundance from samples treated with test compounds was then divided by the normalized FL SMN2mini mRNA abundance from cells treated with vehicle to determine the level of FL SMN2mini mRNA relative to vehicle control.

Table 3 provides EC for full-length SMN2 minigene mRNA production_1.5xConcentrations obtained from 7-point concentration data generated according to the procedure above for a particular compound of the invention.

Particular compounds of the invention showed EC ≦ 1 μ M for full-length SMN2 minigene mRNA production_1.5xAnd (4) concentration.

More particularly, the compounds of the invention showed an EC of ≦ 0.1 μ M for full-length SMN2 minigene mRNA production_1.5xAnd (4) concentration.

Most particular compounds of the invention showed an EC1.5X concentration of ≦ 0.02 μ M for full-length SMN2 minigene mRNA production.

TABLE 3 EC for full-Length SMN2 minigene mRNA production_1.5xAnd (4) concentration.

Measurement 2

Determination of SMN protein in cultured cells

The SMN HTRF (homogeneous time-resolved fluorescence) assay was used to quantify the level of SMN protein in fibroblasts of SMA patients treated with test compounds. The materials used and the respective sources are listed in table 4 below.

Table 4. materials used in SMN protein assay in cultured cells and sources thereof.

Cells were thawed and cultured in DMEM-10% FBS for 72 hours. Cells were trypsinized, counted and resuspended in DMEM-10% FBS to a concentration of 25,000 cells/mL. The cell suspension was plated at 5,000 cells/well in 96-well microtiter plates and incubated for 3 to 5 hours. Test compounds were serially diluted 3.16-fold in 100% DMSO to generate 7-point concentration curves. mu.L of the test compound solution was transferred to wells containing cells and the cells were placed in a cell incubator (37 ℃, 5% CO)₂100% relative humidity) for 48 hours. Triplicate samples were set for each test compound concentration. After 48 hours, the supernatant was removed from the wells and 25 μ L of RIPA lysis buffer containing protease inhibitors was added to the wells and incubated for 1 hour at room temperature with shaking. Add 25 μ L of diluent and then 35 μ LL of the resulting lysate was transferred to 384 well plates, each containing 5. mu.L of antibody solution (1: 100 dilution of anti-SMN d2 and anti-SMN kryptate in SMN reconstitution buffer). The plate was centrifuged for 1 minute to bring the solution to the bottom of the well and then incubated overnight at room temperature. The fluorescence at 665nm and 620nm was measured for each well of the plate on an EnVision multi-label plate reader (Perkin-Elmer).

Normalized fluorescence signals for each sample, blank and carrier control well were calculated by dividing the signal at 665nm by the signal at 620 nm. The normalized signal accounts for possible fluorescence quenching due to matrix effects of the lysate. The Δ F value (a measure of SMN protein abundance as a percentage value) for each sample well was calculated by: the normalized mean fluorescence of the blank control wells was subtracted from the normalized fluorescence of each sample well, and the difference was then divided by the normalized mean fluorescence of the blank control wells and the resulting value was multiplied by 100. The Δ F value for each sample well represents SMN protein abundance from the sample treated with the test compound. The Δ F value for each sample well was divided by the Δ F value for the vehicle control well to calculate the fold increase in SMN protein abundance relative to the vehicle control. Table 5 provides EC against SMN protein expression_1.5xConcentrations obtained from 7-point concentration data generated according to the procedure above for the particular compounds of the invention.

Particular compounds of the invention show EC ≦ 1 μ M for SMN protein expression_1.5xAnd (4) concentration.

More particular compounds of the invention exhibit an EC against SMN protein expression of ≦ 100nM_1.5xAnd (4) concentration.

Most particular compounds of the invention exhibit an EC for SMN protein expression of ≤ 30nM_1.5xAnd (4) concentration.

Table 6 provides the maximal fold increase of SMN protein obtained from 7-point concentration data generated according to the above procedure for a particular compound of the invention.

Particular compounds of the invention showed >1.5 maximal fold increase.

More particular compounds of the invention show a >1.7 maximal fold increase.

Most particular compounds of the invention show a >1.8 maximal fold increase.

TABLE 5 EC for SMN protein expression_1.5xAnd (4) concentration.

Table 6 maximum fold increase of SMN protein.

Claims (56)

1. A compound of formula (I)

Wherein

R¹Is hydrogen or C_1-7-an alkyl group;

R²is hydrogen, cyano, C_1-7Alkyl radical, C_1-7-haloalkyl or C_3-8-a cycloalkyl group;

R³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

a is N-heterocycloalkyl or NR¹²R¹³Wherein N-heterocycloalkyl contains 1 or 2 nitrogen ring atoms and is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹²is heterocycloalkyl containing 1 nitrogen ring atom, wherein heterocycloalkyl is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

R¹⁴independently selected from hydrogen, C_1-7Alkyl, amino-C_1-7Alkyl radical, C_3-8Cycloalkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group;

provided that if A is an N-heterocycloalkyl radical containing only 1 nitrogen ring atom, then at least one R¹⁴The substituent being amino or amino-C_1-7-an alkyl group;

and pharmaceutically acceptable salts thereof.

2. The compound of claim 1, wherein

R¹Is hydrogen or C_1-7-an alkyl group;

R²is hydrogen, cyano, C_1-7Alkyl radical, C_1-7-haloalkyl or C_3-8-a cycloalkyl group;

R³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

a is N-heterocycloalkyl containing 1 or 2 nitrogen ring atoms, wherein N-heterocycloalkyl is optionally substituted with 1,2, 3 or 4 substituents selected from R¹⁴Substituted with the substituent(s);

R¹⁴independently selected from hydrogen, C_1-7Alkyl, amino-C_1-7Alkyl radical, C_3-8Cycloalkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group;

provided that if A is an N-heterocycloalkyl radical containing only 1 nitrogen ring atom, then at least one R¹⁴The substituents being amino or amino-C_1-7-an alkyl group;

and pharmaceutically acceptable salts thereof.

3. The compound of any one of claims 1 or 2, wherein R¹Is C_1-7-an alkyl group.

4. A compound according to any one of claims 1 to 3, wherein R¹Is methyl.

5. A compound according to any one of claims 1 to 4, wherein R²Is hydrogen or C_1-7-an alkyl group.

6. A compound according to any one of claims 1 to 5, wherein R²Is hydrogen or methyl.

7. A compound according to any one of claims 1 to 6, wherein R³Is hydrogen or C_1-7-an alkyl group.

8. A compound according to any one of claims 1 to 7, wherein R³Is hydrogen or methyl.

9. A compound according to any one of claims 1 to 8, wherein R¹²Is optionally substituted by 1,2, 3 or 4 substituents selected from R¹⁴Piperidinyl substituted with the substituent of (1).

10. The compound according to any one of claims 1 to 9, wherein R¹³Is hydrogen or C_1-7-an alkyl group.

11. The compound according to any one of claims 1 to 10, wherein R¹³Is hydrogen or methyl.

12. The compound according to any one of claims 1 to 11, wherein R¹⁴Independently selected from C_1-7Alkyl and heterocycloalkyl or two R¹⁴Together form C_1-7-an alkylene group.

13. The compound according to any one of claims 1 to 12, wherein R¹⁴Independently selected from methyl, ethyl and pyrrolidinyl or two R¹⁴Together form an ethylene group.

14. The compound according to any one of claims 1 to 13, wherein N-heterocycloalkyl in a or R as defined in claim 1¹²The heterocycloalkyl group of (a) is further characterized in that one ring nitrogen atom is basic.

15. A compound according to any one of claims 1 to 14, wherein

A isWherein

X is N or CH;

R⁴is hydrogen, C_1-7-alkyl or- (CH)₂)_m-NR⁹R¹⁰；

R⁵Is hydrogen or C_1-7-an alkyl group;

R⁶is hydrogen or C_1-7-an alkyl group;

R⁷is hydrogen or C_1-7-an alkyl group;

R⁸is hydrogen or C_1-7-an alkyl group;

R⁹and R¹⁰Independently selected from hydrogen, C_1-7-alkyl and C_3-8-a cycloalkyl group;

R¹³is hydrogen, C_1-7-alkyl or C_3-8-a cycloalkyl group;

n is 0, 1 or 2;

m is 0, 1,2 or 3;

or R⁴And R⁵Together form C_1-7-an alkylene group;

or R⁴And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁶Together form C_2-7-an alkylene group;

or R⁵And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁹Together form C_1-7-an alkylene group;

or R⁷And R⁸Together form C_2-7-an alkylene group;

or R⁷And R⁹Together form C_1-7-an alkylene group;

or R⁹And R¹⁰Together form C_2-7-an alkylene group;

provided that if X is CH, then R⁴Is- (CH)₂)_m-NR⁹R¹⁰(ii) a And is

Provided that if X is N and R is⁴Is- (CH)₂)_m-NR⁹R¹⁰And m is 2 or 3.

16. The compound according to any one of claims 1 to 15, wherein a isWherein

X is N or CH;

R⁴is hydrogen, C_1-7-alkyl or- (CH)₂)_m-NR⁹R¹⁰；

R⁵Is hydrogen or C_1-7-an alkyl group;

R⁶is hydrogen or C_1-7-an alkyl group;

R⁷is hydrogen or C_1-7-an alkyl group;

R⁸is hydrogen or C_1-7-an alkyl group;

R⁹and R¹⁰Independently selected from hydrogen, C_1-7-alkyl and C_3-8-a cycloalkyl group;

n is 0, 1 or 2;

m is 0, 1,2 or 3;

or R⁴And R⁵Together form C_1-7-an alkylene group;

or R⁴And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁶Together form C_2-7-an alkylene group;

or R⁵And R⁷Together form C_1-7-an alkylene group;

or R⁵And R⁹Together form C_1-7-an alkylene group;

or R⁷And R⁸Together form C_2-7-an alkylene group;

or R⁷And R⁹Together form C_1-7-an alkylene group;

or R⁹And R¹⁰Together form C_2-7-an alkylene group;

provided that if X is CH, then R⁴Is- (CH)₂)_m-NR⁹R¹⁰(ii) a And is

Provided that if X is N and R is⁴Is- (CH)₂)_m-NR⁹R¹⁰And m is 2 or 3.

17. The compound according to any one of claims 1 to 16, wherein X is N.

18. The compound according to any one of claims 1 to 17, wherein n is 1.

19. The compound according to any one of claims 1 to 18, wherein R⁴Is hydrogen, methyl or- (CH)₂)_m-NR⁹R¹⁰。

20. The compound according to any one of claims 1 to 19, wherein R⁴Is hydrogen.

21. The compound according to any one of claims 1 to 20, wherein R⁵Is hydrogen, methyl or ethyl.

22. The compound according to any one of claims 1 to 21, wherein R⁵Is methyl.

23. The compound according to any one of claims 1 to 22, wherein R⁶Is hydrogen or methyl.

24. The compound according to any one of claims 1 to 23, wherein R⁶Is hydrogen.

25. The compound according to any one of claims 1 to 24, wherein R⁷Is hydrogen or methyl.

26. The compound according to any one of claims 1 to 25, wherein R⁸Is hydrogen.

27. The compound according to any one of claims 1 to 19, wherein m is 0.

28. The compound according to any one of claims 1 to 18, wherein R⁴And R⁵Together form a propylene group.

29. The compound according to any one of claims 1 to 18, wherein R⁵And R⁶Together form an ethylene group.

30. The compound according to any one of claims 1 to 18, wherein R⁹And R¹⁰Together form butylene groups.

31. The compound according to any one of claims 1 to 30, wherein a is selected from the group consisting of:

wherein R is⁴、R⁵、R⁶、R⁷、R⁸And R¹³As defined in any one of claims 1 to 30, and wherein R¹¹Is hydrogen or C_1-7-an alkyl group.

32. The compound according to any one of claims 1 to 31, wherein a is selected from the group consisting of:

wherein R is⁴、R⁵、R⁶、R⁷And R⁸As defined in any one of claims 1 to 31, and wherein R¹¹Is hydrogen or C_1-7-an alkyl group.

33. The compound according to any one of claims 1 to 32, wherein a is selected from the group consisting of: piperazinyl, diazepanyl, pyrrolidinyl, and hexahydropyrrolo [1,2-a ]]Pyrazinyl, each of which is optionally substituted with 1,2, 3 or 4R as defined in any one of claims 1 to 32¹⁴Is substituted with the substituent(s).

34. The compound according to any one of claims 1 to 33, wherein a is selected from the group consisting of: piperazin-1-yl, 1, 4-diazepan-1-yl, pyrrolidin-1-yl and hexahydropyrrolo [1,2-a ]]Pyrazin-2 (1H) -yl, each of which is optionally substituted with 1 or 2R selected from the group as defined in any one of claims 1 to 33¹⁴Is substituted with the substituent(s).

35. The compound according to any one of claims 1 to 31, wherein a is NR¹²R¹³Wherein R is¹²And R¹³The method of any one of claims 1 to 31.

36. The compound according to any one of claims 1 to 31, wherein a isWherein R is⁴、R⁵、R⁶、R⁷、R⁸And R¹³As defined in any one of claims 1 to 31.

37. The compound according to any one of claims 1 to 34, wherein a is selected from the group consisting of:

38. the compound according to any one of claims 1 to 34, wherein a is selected from the group consisting of:

39. the compound according to any one of claims 1 to 38, selected from the group consisting of:

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- (4-methylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5R) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (1, 4-diazepan-1-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (1, 4-diazepan-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -8 a-methyl-1, 3,4,6,7, 8-hexahydropyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (3, 3-dimethylpiperazin-1-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-pyrrolidin-1-ylpyrrolidin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3R) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (3, 3-dimethylpiperazin-1-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3S,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R) -3-ethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

and pharmaceutically acceptable salts thereof.

40. The compound according to any one of claims 1 to 39, selected from the group consisting of:

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aR) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7- [ (3S,5R) -3, 5-dimethylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- [ (8aS) -3,4,6,7,8,8 a-hexahydro-1H-pyrrolo [1,2-a ] pyrazin-2-yl ] -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-7- [ (3S) -3-methylpiperazin-1-yl ] pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

7- [ (3R,5S) -3, 5-dimethylpiperazin-1-yl ] -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

7- (4, 7-diazaspiro [2.5] oct-7-yl) -9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

and pharmaceutically acceptable salts thereof.

41. A compound of formula (VI)

Wherein R is¹、R²And R³The method of any one of claims 1 to 7;

y is halogen or triflate;

and salts thereof.

42. The compound of formula (VI) according to claim 41, wherein Y is fluoro, chloro, bromo, iodo or triflate.

43. The compound of formula (VI) according to claim 41, wherein Y is fluoro.

44. A compound of formula (VI) according to any one of claims 41 to 43, selected from the group consisting of:

7-fluoro-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-pyrido [1,2-a ] pyrimidin-4-one;

7-fluoro-9-methyl-2- (2-methylimidazo [1,2-b ] pyridazin-6-yl) pyrido [1,2-a ] pyrimidin-4-one;

2- (2, 8-dimethylimidazo [1,2-b ] pyridazin-6-yl) -7-fluoro-9-methyl-pyrido [1,2-a ] pyrimidin-4-one;

and salts thereof.

45. For preparing the right toA process for the preparation of a compound of formula (I) as claimed in any one of claims 1 to 40, which process comprises an aromatic nucleophilic substitution reaction between a compound of formula (VI) as claimed in any one of claims 41 to 44 and a compound of formula M-A, wherein A, R is carried out by heating in a solvent¹、R²And R³As defined in any one of claims 1 to 40, Y is as defined in any one of claims 41 to 44, M is hydrogen, sodium or potassium, and wherein M is linked to a via the nitrogen atom of a.

46. The method of claim 45, wherein the aromatic nucleophilic substitution reaction is performed at a temperature of 80 ℃ to 200 ℃.

47. The process according to any one of claims 45 or 46, wherein the solvent of the aromatic nucleophilic substitution reaction is selected from the group consisting of dimethyl sulfoxide, N-methylpyrrolidone, and dimethylformamide.

48. The method of any one of claims 45-47, wherein M is hydrogen.

49. A compound of formula (I) according to any one of claims 1-40 obtainable by a process according to any one of claims 45 to 48.

50. A pharmaceutical composition comprising a compound of formula (I) according to any one of claims 1-40 or a pharmaceutically acceptable salt thereof and one or more pharmaceutically acceptable excipients.

51. A compound of formula (I) or a pharmaceutically acceptable salt thereof, as claimed in any one of claims 1-40 above, for use as therapeutically active substance.

52. A compound of formula (I) or a pharmaceutically acceptable salt thereof according to any one of claims 1-40 for use in the treatment or prevention of Spinal Muscular Atrophy (SMA).

53. A method for the treatment or prevention of Spinal Muscular Atrophy (SMA) comprising administering to a subject a compound of formula (I) or a pharmaceutically acceptable salt thereof as defined above according to any one of claims 1-40.

54. Use of a compound of formula (I) according to any one of claims 1-40 or a pharmaceutically acceptable salt thereof for the treatment or prevention of Spinal Muscular Atrophy (SMA).

55. Use of a compound of formula (I) according to any one of claims 1-40 or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment or prevention of Spinal Muscular Atrophy (SMA).

56. The invention as described above.