TrkB positive allosteric modulators

Abstract

The present invention relates to the field of pharmaceutical compositions comprising "LIT-TB" derivatives of formula I. More particularly, it relates to "LIT-TB" derivatives for use in the treatment of neurodegenerative diseases, more particularly in the treatment of Huntington's disease. The invention also relates to "LIT-TB" derivatives and their preparation.

Description

[Technical Field]

[0001] The present invention relates to the field of pharmaceutical compositions comprising LIT-TB derivatives. More particularly, it relates to LIT-TB derivatives for use in the treatment of neurodegenerative diseases, more particularly in the treatment of Huntington's disease. The invention also relates to LIT-TB derivatives and their preparation. [Background technology]

[0002] Huntington's disease is a genetic disorder that causes the progressive destruction (degeneration) of nerve cells in the brain. Huntington's disease has a wide-ranging impact on a person's functional abilities, usually resulting in movement, thinking (cognitive), and psychiatric disorders.

[0003] Huntington's disease (HD) is a rare, autosomal dominant neurodegenerative disorder characterized by impaired motor control, cognitive impairment, behavioral changes, and mood disturbances. Progressive neurodegeneration of the striatum and other regions, such as the cerebral cortex, leads to death within 10–20 years after the onset of the first symptoms (Non-Patent Document 1).

[0004] Depending on the age of onset, HD can be classified into two forms: the more typical adult-onset HD and the less common juvenile-onset HD (JHD), also known as the Westphal variant of HD. The average age of symptom onset in patients with adult-onset HD is 30–50 years, whereas JHD onset occurs before age 20. Although symptoms overlap somewhat between the two forms, the pattern of motor disturbances differs between adult-onset HD and JHD. Chorea (abnormal involuntary movements) is typically the first symptom observed in patients with adult-onset HD.

[0005] As the disease progresses, partial or complete loss of muscle movement, known as hypokinesia, becomes more apparent. In contrast, hypokinesia is often present from the onset of JHD, while chorea is a less prominent symptom in these patients and may be absent altogether in some cases. Epilepsy is commonly observed in individuals with JHD, but epileptic seizures are not present in adult-onset HD. Symptom severity progresses over time, and the average latency from HD diagnosis to death is 10–20 years in patients with adult-onset HD and less than 10 years in those with JHD.

[0006] HD is caused by a genetic defect that results in the expansion of a cytosine, adenine, and guanine (CAG) repeat within the huntingtin gene (Htt), leading to the production of mutant huntingtin protein (mHtt). Although the function of wild-type huntingtin protein (Htt) remains incompletely understood, mHtt has been demonstrated to exert toxic effects on certain neurons in the brain.

[0007] Htt is localized in multiple cells and expressed ubiquitously throughout the body. Although the function of Htt remains incompletely understood, studies have shown that it interacts with an array of other proteins involved in several cellular processes, including intracellular signaling, metabolism, and gene transcription. In recent years, increasing evidence has suggested that genetic defects in the huntingtin gene disrupt the normal biological function of Htt, which, in addition to the toxic gain of function of mHtt, may play a role in the pathology of HD (Non-Patent Documents 2-4).

[0008] The huntingtin gene is located on chromosome 4p16.3. At the start of the gene in exon 1, there is a series of trinucleotide CAG repeats. These triplet repeats Each repeat encodes the amino acid glutamine, and thus this CAG triplet repeat encodes a stretch of glutamine, also known as a polyglutamine tract (Non-Patent Document 5). Normal huntingtin genes have polyglutamine tracts ranging from 6 to 26 CAG repeats. The number of these CAG repeats is significantly increased in people with HD, and repeats of more than 36 are associated with the onset of HD (Non-Patent Documents 5-6).

[0009] The discovery of huntingtin has provided new insights into the pathogenesis of HD, but the mechanisms that lead to selective death and neuronal loss remain unclear.

[0010] In parallel with research aimed at improving our understanding of the pathogenesis of HD, efforts are being made to find potential therapies for this devastating disease. In this regard, attention has been focused on the use of neurotrophic factors in novel therapeutic strategies for human neurodegenerative diseases (Non-Patent Document 7).

[0011] BDNF is a member of the neurotrophin family of growth factors that specifically binds to the TrkB tyrosine kinase receptor, thus mediating neurotrophic signaling (Non-Patent Documents 8-9). BDNF is the most abundant neurotrophic factor in the adult brain and promotes the survival, growth, and plasticity of various neuronal populations during normal development in the adult brain, as well as subsequent injury. Given its trophic effects on neurons and its central role in higher cognitive functions, BDNF is rapidly emerging as a key element in the pathophysiology of many brain disorders, including neurological disorders, neurodegenerative diseases, and psychiatric disorders.

[0012] The fact that BDNF has pro-survival activity on striatal neurons that die in HD has led to the idea that reduced endogenous trophic support may contribute to the onset and / or progression of the disease. This hypothesis has sparked interest in BDNF and / or BDNF mimetics as potential therapeutic agents, and this has been strengthened by reports of reduced BDNF levels in the cerebral cortex and striatum of people with HD, as well as in many mouse and cell models of this disease (Non-Patent Documents 10-12).

[0013] There is a molecular relationship between huntingtin and BDNF, as normal (but not mutant) huntingtin promotes BDNF production and axonal transport.

[0014] This is due to a reduction in transcription of the BDNF gene. Although no underlying molecular mechanisms have been proposed to explain the reduced neurotrophic support in other neurological disorders such as Parkinson's disease (PD) or Alzheimer's disease (AD), it is known that huntingtin mutations in HD reduce the transcriptional activity of the BDNF promoter and therefore reduce BDNF gene transcription and protein production in the cerebral cortex.

[0015] This has been confirmed in humans by studies carried out in the cerebral cortex, caudate nucleus, and putamen of patients with HD, which also showed reduced BDNF expression in the caudate nucleus and putamen, suggesting that BDNF supplementation may have therapeutic effects in HD.

[0016] While wild-type huntingtin stimulates BDNF gene transcription by acting at the level of the BDNF promoter II, the presence of a pathological CAG expansion in huntingtin abolishes its ability to sustain BDNF transcription in HD.

[0017] This is due to reduced BDNF transport in HD. Biochemical studies of mutant huntingtin knock-in cells, mice, and HD postmortem tissues suggest that B We show that the complex that drives BDNF vesicles is altered in HD. These results may therefore imply that wild-type huntingtin controls the transport of BDNF from the cortex to the striatum and that this transport is affected in HD.

[0018] Many studies in mice and humans tend to attribute the deficit in striatal BDNF in HD to a combination of two factors: reduced production of BDNF in the cortex and reduced transport of this neurotrophin from the cortex to the striatum. In HD, both processes involving normal huntingtin are simultaneously disrupted.

[0019] Furthermore, one report showed that mutant huntingtin affects TrkB levels in HD by showing that TrkB protein levels were reduced in mutant huntingtin knock-in cells and HD mouse models (Non-Patent Document 13). Dramatic reductions in TrkB receptors were also found in the striatum from three HD patients, and reduced TrkB levels were also detected in cortical samples from four HD subjects. Further investigation is needed to understand the extent and consistency of TrkB downregulation.

[0020] To overcome the problems induced by reduced BDNF in HD, experiments were conducted in R6 / 1 mice to evaluate the potential in vivo benefits of BDNF supplementation (Non-Patent Document 14). BDNF was found to effectively increase the expression of enkephalins and the number of enkephalin-expressing striatal cells, which are the cells most affected in HD.

[0021] However, despite these promising results, BDNF supplementation raises several issues: if the amount is too small, it may not be sufficient to produce the desired effect, and if it is too large, it may be dangerous. In fact, uncontrolled BDNF administration may interfere with other mechanisms, such as activity-dependent neuroplasticity, and may induce serious side effects, such as epileptic activity (Non-Patent Document 15).

[0022] Although medications are available to help manage the symptoms of Huntington's disease, there is currently a significant unmet need, as no treatment exists that can prevent the physical, mental, and behavioral decline associated with the condition.

[0023] It is clear that BDNF is one of the key deficient factors in HD, and that increasing endogenous BDNF production may have therapeutic effects, so controlling central and peripheral concentrations of BDNF is crucial. [Prior art documents] [Non-patent literature]

[0024] [Non-Patent Document 1] Vonsattel JP, DiFiglia M., J. Neuropathol. Exp. Neurol., 57, 369-384, 1998. [Non-patent document 2] Li SH, Li XJ.,Multiple pathways contribute to the pathogenesis of Huntington disease.Molecular Neurodegeneration,1,19,2006. [Non-patent document 3] Harjes P., Wanker EE, the hunt for huntingtin function: interaction partners tell many different stories.Trends Biochem.Sci,28,425-433,2003. [Non-patent document 4] Schulte J., Littleton JT, The biological function of the Huntingtin protein and its relevance to Huntington's disease pathology.Current Trends in Neurology,5,65-78,2011. [Non-Patent Document 5] The Huntington's Disease Collaborative Research Group,A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes,Cell,72,971-983,1993. [Non-patent document 6] Roos RAC,Untington's disease: a clinical review;Orphanet Journal of Rare Diseases,5,40,2010. [Non-Patent Document 7] Koliatsos VE, Mocchetti I., Cell Death and Diseases of the Nervous System, Humana Press, Totowa, NJ, 545-591, 1999. [Non-patent document 8] Barbacid M.,Structural and functional properties of the Trk family of neurotrophin receptors,Ann.NYAcad.Sci.,766,442-458,1995. [Non-Patent Document 9] Leibrock J.,Lottspeich F.,Hohn A.,Hofer H.,Hengerer B.,Masiakowski P.,Thoenen H.,Barde YA,Molecular cloning and expression of brain-derived neurotrophic factor,Nature,341,149-152,1989.

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Non-Patent Document 14

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Non-Patent Document 16

[0025] [Figure 1]These figures show the effects of LIT-TB001 on Trk phosphorylation, ERK phosphorylation, and neurite outgrowth in the presence of NGF / TrkA or BDNF / TrkB. Nnr5PC12-TrkA and nnr5PC12-TrkB cells are NGF-unresponsive mutant PC12 cells stably transfected with TrkA and TrkB, respectively (Non-Patent Document 16). As previously described, TrkA and TrkB activation in nnr5PC12-TrkB or -TrkA cells was assessed by quantifying the level of phospho-Trk at tyrosine 706 (Y706) after the addition of BDNF (1 nM) or NGF (2 nM), respectively, in the presence or absence of various concentrations (0.1, 10, and 1000 nM) of TB001 for 15 minutes (Non-Patent Document 17). Activation of downstream signaling pathways was assessed by quantifying phospho-ERK in the same cells. As previously described, neurite outgrowth was determined 48 hours after initial treatment by counting the number of cells bearing neurites longer than two cells in diameter (17). In all three assays, LIT-TB001 showed high selectivity for TrkB signaling, as demonstrated by increases in phospho-Trk, phospho-ERK, and neurite outgrowth induced by BDNF, but not NGF. [Figure 2] Figure 1 shows the intracellular inhibition of catalytic activity of 45 kinases (ExpressS Diversity Kinase Panel, Eurofins Discovery, item no. P10) by LIT-TB001 at a concentration of 10 μM. The effect of the compounds on ATP-induced kinase-mediated substrate phosphorylation for each kinase is measured by TR-FRET LANCE technology. [Figure 3]The effect of acute intraperitoneal administration of LIT-TB001 (0, 0.5, and 1.0 mg / kg) on ​​TrkB phosphorylation in TrkB-expressing regions of the mouse brain is shown. Left: Adult C57BL / 6 male mice were intraperitoneally injected with saline (0.9% NaCl) or LIT-TB001 (0.5 or 1 mg / kg). One hour later (unless otherwise noted), the mice were decapitated, blood was collected, and the brains were rapidly removed on ice. The cortex and hippocampus were then dissected, and the tissues were immediately processed for Western blot analysis using a phospho-Y806-TrkB-selective antibody (Non-Patent Document 17). Representative Western blots performed on the cortex of mice intraperitoneally injected with saline solution or TB001 (0.5 or 1 mg / kg) for 1 hour are shown. An anti-TrkB antibody is used to quantify the total amount of TrkB. Anti-tubulin is used as a loading control. Right: Quantification of phospho-TrkB in the hippocampus and cortex of mice after LIT-TB001 injection shows significant TrkB enhancement in vivo compared to saline treatment (*p<0.05, **p<0.01, one-way ANOVA). TrkB phosphorylation levels are calculated as the ratio between the phospho-TrkB band and the total TrkB band in each region. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention enables new therapeutic solutions based on positive allosteric modulators (PAMs) of TrkB.

[0027] This refers to "positive allosteric modulators" (PAMs), also known as allosteric enhancers or potentiators, i.e., compounds that induce an amplification of the effect of a receptor's response to a primary ligand without directly activating the receptor. Within the present invention, PAM TrkB activity relates to the enhancement of BDNF effects on the functional activity of TrkB receptors, measured in vitro or in vivo by means of specific TrkB receptor phosphorylation assays.

[0028] The compounds and compositions of the invention have several properties such as effects on neurite outgrowth, BDNF enhancement, BBB (blood-brain barrier) penetration, good brain bioavailability, increased cell survival, TrkB selectivity, and neuroprotective effects, giving this potential PAM an interesting drug profile that can address several neurodegenerative pathologies such as Huntington's disease, Parkinson's disease, and Alzheimer's disease.

[0029] The compounds and compositions of the invention may potentiate the TrkB-mediated functional effects of BDNF, opening up new therapeutic avenues for the treatment of HD.

[0030] In a first aspect, the invention provides a pharmaceutical composition comprising: (a) a LIT-TB compound of formula I,

[0031] [ka]

[0032] During the ceremony, R 1 is selected from the group including H, halogen, C1-C10 saturated or unsaturated substituted or unsubstituted aliphatic, heteroaliphatic, cyclic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl groups, or R 1 is a group of formula Ia,

[0033] [ka]

[0034] During the ceremony, R A is a linear C1-C10 alkyl chain optionally interrupted by one or more ether or amide functional groups; A 2 is an amide functional group, R B is an optionally branched C1-C6 alkyl chain; fl is a fluorescent group or a non-fluorescent analogue thereof; G is a bond or -G 1 -G 2 represents a linker, G 1 is a bond or a C1-C4 substituted or unsubstituted alkyl chain optionally containing a heteroatom such as N or O; G 2 C1-C10 saturated or unsaturated, substituted or unsubstituted aliphatic, heteroaliphatic, cyclic represents an alicyclic, heteroalicyclic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl group of the formula: Same or different X 1 and X 2 independently represent CH or N; X 3 is C or N, X 4 is N or NH, Y represents N or CH; r is an integer from 1 to 3, A is an amide or amine functional group, preferably A is C(O)NH, NHC(O), or NH; m is equal to 0, 1, or 2, m' is equal to 0, 1, or 2, and m+m'≦3; t is an integer from 0 to 5, Each R may be the same or different 6 The group is selected from the group comprising H, fluoride, optionally branched C1-C6 alkyl chains and C1-C6 alkoxy groups; Same or different T 1 and T 2 However, CH2 and CHR are independent 6 or C=O, wherein Z is selected from the group comprising a bond, H, and an optionally branched C1-C3 alkyl chain optionally containing a heteroatom selected from the group comprising O or N, If Z is H, then R 2 is zero or R 2is H and a 5- or 6-membered aromatic or non-aromatic ring, or optionally one or more R 7 each R 7 groups are selected from the group consisting of H, halides, CN, NO2, NH2, CONH2, optionally branched C1-C6 alkyl chains, and optionally branched C1-C6 alkoxy groups, and two R 7 LIT-TB compounds of formula I, wherein the groups are optionally covalently linked to form a ring; or a pharmaceutically acceptable salt thereof; (b) a pharmaceutically acceptable excipient or carrier.

[0035] In this disclosure,

[0036] [ka]

[0037] is X 3 and X 4 represents a single or double bond depending on the nature of the bond, and the adjacent bond may be a single or double bond.

[0038] In this disclosure,

[0039] [ka]

[0040] represents the group and its point of attachment to the main molecule.

[0041] Pharmaceutically acceptable salts of the compounds of formula I include the acid addition and base salts thereof. Suitable acid addition salts are formed from acids, which form non-toxic salts. Examples include acetate, aspartate, benzoate, besylate, bicarbonate / carbonate, bisulfate / sulfate, borate, camsylate, citrate, edisylate, esylate, formate, fumarate, gluceptate, gluconate, glucuronate, hexafluorophosphate, hybenzate, hydrochloride / chloride, hydrobromide / bromide, hydroiodide / iodide, isethionate, lactate, malate, maleate, malonate, mesylate, methyl sulfate, naphthylate, 2-napsylate, nicotinate, nitrate, orotate, oxalate, palmitate, pamoate, phosphate / hydrogen phosphate / dihydrogen phosphate, saccharate, stearate, succinate, tartrate, tosylate, and trifluoroacetate, and xinafoate salts. For a discussion of suitable salts, see Physicians of the United States, 1999, pp. 111-114, 2000.

[0042] In general, the term "substituted," whether preceded by the term "optionally" or not, and the substituents contained in the formulae of the present invention, refer to the replacement of hydrogen radicals of a given structure with the radical of a specified substituent. When more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituents can be either the same or different at all positions. As used herein, the term "substituted" is considered to include all permissible substituents of organic compounds.

[0043] As used herein, the term "aliphatic" refers to a non-aromatic group. Aliphatic groups may be cyclic. Aliphatic groups may be saturated, such as hexane, or unsaturated, such as hexene and hexyne. Open-chain groups (whether straight-chain or branched) do not contain rings of any kind and are therefore aliphatic. Aliphatic groups may be saturated (alkanes) linked by single bonds or unsaturated with double bonds (alkenes) or triple bonds (alkynes). "Heteroaliphatic" groups are aliphatic groups bearing one or more heteroatoms, with oxygen, nitrogen, and sulfur being the most common.

[0044] As used herein, the term "alkyl" refers to straight-chain and branched alkyl groups. A similar convention applies to other generic terms, such as "alkenyl," "alkynyl," and the like. In certain embodiments, as used herein, "lower alkyl" is used to refer to an alkyl group (substituted, unsubstituted, branched, or unbranched) having about 1 to 6 carbon atoms. Exemplary alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, tert-pentyl, n-hexyl, and sec-hexyl; such moieties may also bear one or more substituents. Alkyl groups include, but are not limited to, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, and the like. Representative alkynyl groups include, but are not limited to, ethynyl, 2-propynyl (propargyl), 1-propynyl, and the like.

[0045] Generally, as used herein, the term "aromatic moiety" or "aryl" refers to a stable substituted or unsubstituted unsaturated monocyclic or polycyclic hydrocarbon moiety, preferably having 3 to 14 carbon atoms, containing at least one ring that satisfies the Hackle rules for aromaticity. Examples of aromatic moieties include, but are not limited to, phenyl, indanyl, indenyl, naphthyl, phenanthryl, and anthracyl. "Heteroaryl" is both heterocyclic and aromatic.

[0046] As used herein, the term "halogen" refers to an atom selected from fluorine, chlorine, bromine, and iodine.

[0047] As used herein, the term "independently" refers to the fact that the substituents, atoms, or moieties to which these terms refer are selected from a list of variables that are independent of each other (i.e., they can be the same or the same).

[0048] As one of skill in the art would understand, all numerical values, including those expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like, are approximations and are understood to be optionally modified in all instances by the term "about." These values ​​may vary depending upon the desired properties sought to be obtained by one of ordinary skill in the art utilizing the teachings of the description herein. It is also understood that such values ​​inherently contain variability necessarily resulting from the standard deviation found in their respective testing measurements.

[0049] The skilled artisan will also readily recognize that when moieties are grouped together in a common manner, such as in a Markush group, the invention encompasses not only the entire group recited as a whole, but also each member of the group individually and all possible subgroups of the main group. Additionally, for all purposes, the invention encompasses not only the main group but also the main group in which one or more of the group members are absent. Thus, the invention contemplates the explicit exclusion of any one or more members of a recited group. Thus, provisos may be applied to any of the disclosed categories or embodiments, whereby any one or more of the recited elements, species, or embodiments may be excluded from such category or embodiment, for example, when used in an explicit non-limiting sense.

[0050] Advantageously, the LIT-TB compound is R 1 is selected from the group of compounds of formula I, including H, C1-C10 saturated or unsaturated, substituted or unsubstituted aliphatic, heteroaliphatic, cyclic, alicyclic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl groups. 1 may be selected from the group including H, alkyl groups (e.g., methyl, ethyl), cycloalkyl (e.g., cyclopropyl, cyclopentyl), aralkyl (e.g., benzyl, phenethyl), heterocycloaryl (e.g., piperidine), or heteroaryl (e.g., pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,2,4-triazinyl, 1,3,5-triazinyl, oxazolyl, imidazolyl), and R 1 is optionally replaced.

[0051] Advantageously, the LIT-TB compound is R 1is the fluorescent group f1. The fluorescent group f1 may be selected from the group including BDP 558 / 568, BDP 581 / 591, BDP 630 / 650, BDP R6G, BDP FL, BDP TMR, BDP TR, coumarin 343, cyanine 3, cyanine 3.5, cyanine 5, cyanine 5.5, cyanine 7, cyanine 7.5, DY-647P1, fluorescein, sulfo-cyanine 3, sulfo-cyanine 5, sufocyanine 5.5, sulfo-cyanine 7, sulfo-cyanine 7.5, pyrene, rhodamine X, derivatives thereof, or non-fluorescent analogs thereof.

[0052] This refers to a "fluorescent group" (or fluorophore), which is a group that can re-emit light upon photoexcitation. Fluorophores typically contain several linked aromatic groups, or planar or cyclic molecules with several π bonds.

[0053] As used herein, a "derivative" is a compound or group derived from a similar compound by chemical reaction. As an example, a fluorescent group may often be an NHS ester before conjugation. A fluorescent derivative when grafted onto a compound is the same group, but with an NHS moiety. has no share.

[0054] Advantageously, the LIT-TB compound is one in which G is a bond or G 1 is a bond or a C1-C4 substituted or unsubstituted alkyl chain optionally containing a heteroatom such as N or O, and G 2 represents a C1 to C10 saturated or unsaturated, substituted or unsubstituted aliphatic, heteroaliphatic, cyclic, alicyclic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl group; 1 -G 2 -representing a linker, can be selected from the group of compounds of formula I. Preferably, G 1 may be a bond, and G 2can be a saturated or unsaturated, substituted or unsubstituted C2-C6 aliphatic or heteroaliphatic group, or a saturated or unsaturated, substituted or unsubstituted 5-, 6-, or 7-membered ring or heterocycle.

[0055] Advantageously, the LIT-TB compound is R 1 A selection may be made in the group of compounds of formula I in which -G- is linked to the remainder of the molecule via a heteroatom, preferably a nitrogen heteroatom.

[0056] Advantageously, the LIT-TB compound is R 1 -G- may be selected from the group of compounds of formula I in which -G- is selected from the group comprising groups of the following formula:

[0057] [ka]

[0058] Advantageously, the LIT-TB compound is R 1 -G- may be selected from the group of compounds of formula I in which -G- is selected from the group comprising groups of the following formula:

[0059] [ka]

[0060] Advantageously, the LIT-TB compounds comprise the same or different X 1 and X 2 may be selected from the group of compounds of formula I, which may independently represent CH or N.

[0061] Advantageously, the LIT-TB compound is X 3 may be selected from the group of compounds of formula I, which may represent C or N.

[0062] Advantageously, the LIT-TB compound is X 4 may be selected from the group of compounds of formula I which may represent N.

[0063] Advantageously, the LIT-TB compound is X 4is N or NH, then X 1 , X 2 , and X 3 In this group of compounds, at least one of X is N. 4 If it contains nitrogen, X 1 , X 2 , X 3 may also contain no carbon atoms.

[0064] Advantageously, X 1 and X 2 does not simultaneously represent CH.

[0065] Advantageously, the LIT-TB compound is X 4 is N or NH. Preferably, X 4 If NH, then X 3 is C. Preferably, the LIT-TB compound is 3 is N and X 4 may be selected from the group of compounds of formula I in which is N.

[0066] Advantageously, A may be an amide or amine functional group, preferably A is -C(O)NH-, -NHC(O)- or -NH-. Preferably, A is an amide group.

[0067] Advantageously, m may be equal to 0, 1 or 2, and m' may be equal to 0, 1 or 2, with m+m'≦3. Preferably, m=m'=1.

[0068] Advantageously, t may be an integer between 0 and 5. Preferably, t is 0, 1 or 2.

[0069] Advantageously, identical or different T 1 and T 2 are CH2, CHR independently 6 , or C=O.

[0070] Advantageously, the LIT-TB compound comprises one or more R6 R 6 The bond from to the center of the ring is such that any available position within this ring is T 1 and T 2 R containing 6 It indicates that the carbon atom on the ring can carry an R group. 6 When carrying a group, R 6 The group replaces the H generated by that carbon atom. 6 The groups may be the same or different and may be selected from the group including H, fluoride, optionally branched C1-C6 alkyl chains, and optionally branched C1-C6 alkoxy groups. Preferably, m=1 and m'=1, t is 0, 1, or 2, and R 6 is F, Cl, Me or OMe, and T 1 is CH2 or C=O, and T 2 is CH2.

[0071] Advantageously, Z may be selected from the group comprising a bond, H, and an optionally branched C1-C3 alkyl chain optionally containing a heteroatom selected from the group comprising O or N. Preferably, Z is -CH2-, -CH2-CH2-, or -CH2-CH2-CH2-, or Z is -(CH2) n and n is 1, 2, or 3.

[0072] Advantageously, the LIT-TB compound is R 2 is selected from the group including H, cycloalkyl (e.g., cyclopentyl), aralkyl (e.g., benzyl, phenethyl), heterocycloaryl (e.g., piperidinyl, piperazyl), or heteroaryl (e.g., pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,2,4-triazinyl, 1,3,5-triazinyl, oxazolyl, imidazolyl, furyl, thienyl, pyrrolyl, thiazolyl, pyrazolyl, 1,3,4-oxadiazolyl, 1,3,4-thiadiazolyl). 2 is one, two, or three R 7 The group is substituted.

[0073] Advantageously, the LIT-TB compound is R 2 is selected from the group of compounds of formula I including H, cycloalkyl (e.g., cyclopentyl), aralkyl (e.g., benzyl, phenethyl), heterocycloaryl (e.g., piperidine), or heteroaryl (e.g., pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,2,4-triazinyl, 1,3,5-triazinyl, oxazolyl, imidazolyl). 2 is one, two, or three R 7 The group is substituted.

[0074] Advantageously, R 2 may be selected from the group of formula Ib below:

[0075] [ka]

[0076] Each R 7a , R 7b , R 7c may be independently selected from the group including H, F, Cl, Me, OMe, Et, Pr, iPr, Bu, CN, NO2, NH2, CONH2.

[0077] Advantageously, G 1 may be a bond, and G 2 is -Y1(R 4 )-R 3 -Y 2 (R 5 ), and the LIT-TB compound may be selected from the group of compounds of formula II:

[0078] [ka]

[0079] During the ceremony, R 1 , X 1 , X 2 , X 3 , X 4,r,A,m,m',t,R 6 , T 1 , T 2 , Z, and R 2 is defined as above, Same or different Y 1 , Y 2 , and Y 3 independently represent N of CH, Same or different R 4 and R 5 are independently selected from the group comprising optionally branched C1-C3 alkyl groups optionally containing heteroatoms selected from the group comprising H, O and N, and optionally R 4 and R 5 may be covalently linked together to form a cyclic moiety, R 3 is a linear or branched C2 to C6 alkyl chain.

[0080] Advantageously, G 1 may be a bond, and G 2 -Y 1 (R 4 )-R 3 -Y 2 (R 5 ), and the LIT-TB compound may be selected from the group of compounds of formula IIa:

[0081] [ka]

[0082] During the ceremony, R 1 , X 1 , X 2 , X 3 , X 4 ,r,A,m,m',t,R 6 , Z, R 2 , Y 1 , Y 2 , Y 3 , R 3 , R 4 , and R 5 is defined as above.

[0083] Advantageously, G 1 may be a bond, and G 2 teeth,

[0084] [ka]

[0085] and the LIT-TB compound may be selected from the group of compounds of formula III:

[0086] [ka]

[0087] During the ceremony, R 1 , X 1 , X 2 , X 3 , X 4 , Y 1 , Y 2 , Y 3 ,r,A,m,m',t,R 6 , T 1 , T 2 , Z, and R 2 is defined as above.

[0088] Advantageously, G 1 may be a bond, and G 2 teeth,

[0089] [ka]

[0090] and the LIT-TB compound may be selected from the group of compounds of formula IIIa:

[0091] [ka]

[0092] During the ceremony, R 1 , X1 , X 2 , X 3 , X 4 , Y 1 , Y 2 , Y 3 ,r,A,m,m',t,R 6 , Z, and R 2 is defined as above.

[0093] Advantageously, X 3 and X 4 is N and Y 2 is NH and G 1 may be a bond, and G 2 is Y 1 (R 4 )-CH2-CH2-NH, and the LIT-TB compound may be selected from the group of compounds of formula IV,

[0094] [ka]

[0095] During the ceremony, R 1 , R 4 , X 1 , X 2 , Y 1 , Y 3 ,r,A,m,m',t,R 6 , T 1 , T 2 , Z, and R 2 is defined as above.

[0096] Advantageously, X 3 and X 4 is N and Y 2 is NH and G 1 may be a bond, and G 2 is Y 1 (R 4 )-R 3 -CH2-CH2-NH-, and the LIT-TB compound may be selected from the group of compounds of formula IVa:

[0097] [ka]

[0098] During the ceremony, R 1 , R 4 , X 1 , X 2 , Y 1 , Y 3 ,r,A,m,m',t,R 6 , Z, and R 2 is defined as above.

[0099] Advantageously, the composition may comprise a pharmaceutically acceptable excipient or carrier. In the context of the invention, any pharmaceutically acceptable excipient or carrier may be used.

[0100] Advantageously, the composition may be an aqueous composition.

[0101] Advantageously, the pH of the composition may be comprised in the range of 5 to 9.

[0102] Advantageously, the concentration of the LIT-TB compound of formula I, II, III or IV in the composition may be comprised in the range of 1 picoM to 100 μM.

[0103] In this application, when a range is defined, the lower and upper limits are included.

[0104] Advantageously, the composition according to the invention may enable a synergistic effect at a concentration of 10 nM of the LIT-TB derivative that is 10% or more better, preferably 20% or more better, more preferably 30% or more better than the BDNF response at 0.4 nM.

[0105] Advantageously, the half maximal effective concentration (EC50) in the TrkB phosphorylation assay is 10 microM or less.

[0106] Advantageously, the selectivity is greater than 50 compared to the positive allosteric modulation of the related TrkA and TrkC receptors.

[0107] In another aspect, the invention relates to a pharmaceutical composition comprising a LIT-TB compound of formula I, II, IIa, III, IIIa, IV or IVa as defined above for use in a medicament or medicine.

[0108] A third aspect of the invention is a pharmaceutical composition comprising a LIT-TB compound of formula I, II, IIa, III, IIIa, IV, or IVa as defined above for use in the treatment of neurodegenerative diseases, metabolic disorders, mood disorders, spinal cord injury, stroke, and ischemia.

[0109] In the context of the invention, neurodegenerative diseases may be, for example, but not limited to, Alzheimer's disease, amyotrophic lateral sclerosis, Friedreich's disease, Huntington's disease, Lewy body disease, Parkinson's disease, spinal muscular atrophy; metabolic disorders may be, for example, but not limited to, obesity, type 2 diabetes; and mood disorders may be, for example, but not limited to, depression, anxiety, schizophrenia, bipolar disorder, autism spectrum disorder.

[0110] The terms "treating," "treat," and "treatment" include (i) preventing the occurrence of a disease, pathological condition, or medical condition (e.g., prophylaxis); (ii) inhibiting or arresting the development of a disease, pathological condition, or medical condition; (iii) alleviating a disease, pathological condition, or medical condition; and / or (iv) reducing symptoms associated with a disease, pathological condition, or medical condition. Thus, the terms "treat," "treatment," and "treating" extend to prophylaxis and include preventing, preventing, preventing, reducing, halting, or reversing the progression or severity of the condition or symptom being treated. Thus, the term "treatment" includes medical, therapeutic, and / or prophylactic administration, as appropriate.

[0111] "Effective amount" refers to an amount effective for treating a disease, disorder, and / or condition, or for producing a recited effect. For example, an effective amount can be an amount effective for reducing the progression or severity of the condition or symptom being treated. Determining a therapeutically effective amount is well within the capabilities of those skilled in the art. The term "effective amount" is intended to include, for example, an amount of a compound described herein, or an amount of a combination of five compounds described herein, that is effective for treating or preventing a disease or disorder in a host, or for treating the symptoms of a disease or disorder. Thus, "effective amount" generally refers to an amount that provides a desired effect.

[0112] In a fourth aspect, the invention relates to compounds of formula I, II, III, or IV as defined above, excluding N-(1-benzyl-4-piperidyl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide and N-(1-benzyl-4-piperidyl)-3-[6-(1-piperidyl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide.

[0113] Other advantages may also be apparent to the skilled person upon reading the following examples illustrated by the accompanying figures, which are given for illustrative purposes only and are not exhaustive. [Example]

[0114] I. Synthesis method The following synthetic methods and schemes illustrate general procedures by which the compounds of the present invention may be prepared. Starting materials were obtained from commercial sources or were prepared using methods well known to those skilled in the art. The compounds of the present invention were prepared by using the following methods. For example, the compounds of the present invention can be prepared according to the synthetic routes detailed in the Examples section or by synthetic methods similar thereto. In particular, compounds of general formula (I) and pharmaceutically acceptable salts thereof, in which X represents a halogen and R represents any group at the corresponding position in general formula (I), can be synthesized according to the methods described in the following schemes. Although the numbering of the group R in the following schemes differs from the group designation in general formula (I), it will be understood that these schemes describe the preparation of compounds of formula (I), and therefore, these groups R are defined according to the group corresponding to the same position of bond in general formula (I). Purification of intermediates and final products was carried out via normal or reverse phase chromatography using a Dionex UltiMate300 with the following parameters: flow rate of 0.5 mL / min, column temperature: 30 °C, solvent system: A (MeOH) and B (0.05% TFA in HO), t = 0 min to 1 min: 50-60% B, then t = 1 min to t = 10 min: 60-100% B, t = 10 min to t = 15 min: 100% B.

[0115] General Procedure A Condensation of N-aralkylpiperidine analog 1 with cyclic anhydride 2 gave propanoic acid (or homologous) derivatives 4a–c. Starting from ethyl malonyl chloride, alkaline hydrolysis of the ester group followed by condensation afforded 2-[(1-benzylpiperidin-4-yl)carbamoylacetic acid 4c. Peptide-type coupling of the above compound 4 with commercially available 3-chloro-6-hydrazinypyridazine gave hydrazide derivative 6, which was then cyclized to triazolopyridazine 7 under strongly acidic conditions at 135 °C. Coupling of 6-chloro-[1,2,4]triazolo[4,3-b]pyridazine derivative 7 with various heterocyclic secondary amines 8 under basic conditions finally afforded the final compounds of formulas 9–14 (Scheme 1).

[0116] [ka]

[0117] Conditions: a) succinic anhydride or glutaric anhydride, EtOAc, 25°C, 12 hours; b) ethyl malonyl chloride, DCM, Et3N, 25°C; c) NaOH / MeOH, followed by 2N HCl → pH 6 d) BOP, NMM, DCM, 12 hours; e) AcOH, 135 °C, 2 hours; f) 8a-g, Et3N, EtOH, 135 °C, 2 hours or reflux, 12 hours.

[0118] 4-((1-benzylpiperidin-4-yl)amino)-4-oxobutanoic acid 4a (m'=1, m=1, n=1, r=1) Succinic anhydride 2a (1.5 equiv., 394 mg, 3.94 mmol) was solubilized in EtOAc (5 mL). 4-Amino-1-benzylpiperidine 1a (1 equiv., 526 mg, 0.566 mL, 2.63 mmol) was added, and the reaction mixture was stirred at room temperature overnight (18 h) to give carboxylic acid 4a. The white precipitate was filtered and washed with EtOAc (m = 763 mg, yield = 100%). 1 H NMR(400MHz,DMSO-d6)δ7.76(d,J=7.7Hz, 1 H),7.35-7.22(m,5H),3.51(dtd,J=11.0,7.0,3.9Hz,1H),3.45(s,2H),2.77-2.71(m,2H),2.42-2.37(m,2 H),2.31-2.26(m,2H),2.00(ddd,J=11.8,9.2,2.5Hz,2H),1.68(dd,J=12.9,3.9Hz,2H),1.42-1.31(m,2H). 13 C NMR (101MHz, DMSO-d6) δ173.8,170.2,138.4,128.8,128.2,126.9,62.1,51.9,45.9,31.5,30.1,29.2.

[0119] N-(1-benzylpiperidin-4-yl)-4-(2-(6-chloropyridazin-3-yl)hydrazinyl)-4-oxobutanamide (6a) (m'=1, m=1, n=1, r=1) [(1-benzylpiperidin-4-yl)carbamoyl]propanoic acid 4a (1 equiv., 285 mg, 0.982 mmol) and BOP (1.2 equiv., 520 mg, 1.18 mmol) were suspended in DMF (6.3 mL). NMM (1.5 equiv., 148 mg, 0.162 mL, 1.47 mmol) was added and the reaction mixture was stirred at room temperature for 15 min. 3-chloro-6-hydrazinylpyridazine 5 (1.2 equiv., 170 mg, 1.18 mmol) was then added and the reaction mixture was stirred at room temperature overnight (20 h).

[0120] MeOH and silica were added, and the crude material was evaporated. The compound adsorbed on silica was then purified by silica gel chromatography (eluent MeOH / EtOAc / EtN; 1 / 9 / 0.3) to give compound 6a as a yellow solid (m = 379 mg, yield = 93%). 1 H NMR (500MHz, methanol-d4) δ7.47(d,J=9.5Hz,1H),7.39-7.31(m,5H),7.13(d,J=9.5Hz,1H),3.78 -3.70(m,3H),3.03(d,J=11.4Hz,2H),2.60-2.40(m,6H),1.94-1.87(m,2H),1.64-1.54(m,2H). 13 C NMR (126 MHz, methanol-d₄) δ 174.7, 173.8, 161.5, 149.6, 131.28, 131.27, 129.66, 129.65, 129.4, 118.4, 63.2, 52.9, 47.0, 31.5, 31.4, 29.9.

[0121] N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (m'=1, m=1, n=1, r=1) A microwave vial was charged with N-(1-benzylpiperidin-4-yl)-3-[N'-(6-chloropyridazin-3-yl)hydrazinecarbonyl]propanamide 6a (1 equiv., 361 mg, 0.866 mmol) and acetic acid (2 mL). The vial was capped appropriately and the mixing vessel was heated at 135°C for 2 h. The mixture was cooled to room temperature and evaporated. The crude material was co-evaporated with cyclohexane and purified by silica gel chromatography (EtOAc / M Purification by elution with hexane / Et3N, 9 / 1 / 0.3 gave compound 7a as a white solid (m=289 mg, yield=84%). 1 H NMR (400MHz, methanol-d4) δ8.22(d,J=9.7Hz,1H),7.40(d,J=9.7Hz,1H),7.37-7.27(m,5H),3.73-3.62(m,3H),3.43(t,J=7.4Hz,2H) ),2.97(dt,J=12.4,3.9Hz,2H),2.83(t,J=7.3Hz,2H),2.36-2.26(m,2H),1.91-1.83(m,2H),1.56(dtd,J=13.3,11.2,3.8Hz,2H). 13 C NMR (101 MHz, methanol-d₄) δ 173.0, 151.2, 150.9, 144.5, 136.9, 131.0, 129.5, 128.9, 127.2, 124.6, 63.5, 53.0, 47.4, 32.9, 31.7, 21.0. LC-MS [M+H] + =399.17

[0122] Example 1: N-(1-benzylpiperidin-4-yl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 9a (LIT-TB001) N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 191 mg, 0.479 mmol) was solubilized in EtOH (2.5 mL). 1-Methylpiperazine 8a (2 equiv., 95.9 mg, 0.106 mL, 0.958 mmol) and EtN (2 equiv., 96.9 mg, 0.133 mL, 0.958 mmol) were added, and the reaction was heated to reflux overnight. The product was evaporated and diluted with MeOH. HCl (2 M) in EtO (excess) was added, and the reaction was stirred at room temperature for 1.5 h. The mixture was evaporated and crudely purified by silica gel chromatography using a gradient (AcOEt / MeOH / EtN; 9 / 1 / 0.5 to 5 / 1 / 0.5), salified, and lyophilized to give 9a (LIT-TB001) as a yellowish solid (m = 221.2 mg, yield = 86%). 1 H NMR (400MHz, methanol-d4) δ7.87(d,J=10.2Hz,1H),7.33-7.23(m,6H),3.66-3.59(m,5H),3.49(s,2H),3.35-3.32(m,2H),2.82(dt,J=12.0,3.6 Hz,2H),2.75(dd,J=8.0,7.1Hz,2H),2.58(t,J=5.1Hz,4H),2.35(s,3H),2.09(td,J=11.8,2.6Hz,2H),1.82-1.75(m,2H),1.52-1.41(m,2H). 13 C NMR (101 MHz, methanol-d₄) δ 173.2, 156.7, 150.0, 143.9, 138.6, 130.7, 129.3, 128.4, 124.7, 116.5, 63.7, 55.4, 53.3, 47.9, 46.4, 46.1, 33.2, 32.3, 21.2. LC-MS(ESI)[M+H] + =463.29

[0123] N-(1-benzylpiperidin-4-yl)-3-[6-(piperidin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 9b (LIT-TB002) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 38 mg, 0.0953 mmol), piperidine 8b (2 equiv., 16.4 mg, 19 μL, 0.191 mmol), and EtN (2 equiv., 19.3 mg, 26.5 μL, 0.191 mmol) in EtOH (0.6 mL). The crude material was evaporated. A solution of (HO / MeOH; 9 / 1, 1 mL) was added to form a solid. The solid was sonicated and triturated in the presence of heptane, then filtered and washed with heptane to give the desired product as a beige solid. The filtrate was evaporated and purified by reverse phase chromatography (H2O / MeOH) to give the product Both crops were combined, salified, and lyophilized to give 9b (LIT-TB002) as a beige solid (m = 24.5 mg, yield = 53%). 1 H NMR (400MHz, methanol-d4) δ7.82(d,J=10.2Hz,1H),7.33-7.23(m,6H),3.66-3.62(m,5H),3.51(s,2H),3.34-3.31(m,2H),2.84(d, J=11.6Hz,2H),2.75(t,J=7.7Hz,2H),2.11(t,J=11.7Hz,2H),1.80(d,J=13.1Hz,2H),1.75-1.67(m,6H),1.47(q,J=11.9Hz,2H). 13 C NMR (101 MHz, methanol-d₄) δ 173.3, 156.7, 149.9, 143.8, 138.5, 130.7, 129.3, 128.4, 124.3, 116.9, 64.0, 53.3, 48.0, 47.9, 33.2, 32.3, 26.5, 25.5, 21.2. LC-MS(ESI)[M+H] + =448.19

[0124] N-(1-benzylpiperidin-4-yl)-3-[4-benzylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propane-amide 9c, (LIT-TB005) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 100 mg, 0.25 mmol), 1-benzylpiperazine 8c (2 equiv., 88.3 mg, 87 μL, 0.5 mmol), and EtN (2 equiv., 50.7 mg, 70 μL, 0.50 mmol) in EtOH (1.2 mL). The reaction mixture was heated at 135 °C for 2 h. The crude product was evaporated, purified by silica gel flash chromatography (EtOAc / MeOH / EtN: 9 / 1 / 0.5), salified, and lyophilized to give 9c (LIT-TB005) as a brown solid (m = 74 mg, yield = 55%). 1 H NMR (400MHz, methanol-d4) δ7.76(d,J=10.2Hz,1H),7.30-7.12(m,11H),3.57-3.51(m,4H),3.49(s,2H),3.45(s,2H),3.22( t,J=7.5Hz,2H),2.76(dt,J=12.4Hz,J=2.8Hz,2H),2.64(t,J=7.5Hz,2H),2.55-2.46(m,4H),2.09-2.00(m,2H),1.69(dt J=12.8Hz,J=3.8Hz,2H),1.37(qd,J=11.8Hz,J=2.8Hz,2H). 13 C NMR (101 MHz, methanol-d4) δ 171.8, 168.7, 164.0, 155.4, 148.6, 145.3, 142.5, 137.1, 137.0, 129.3, 129.2, 128.0, 127.9, 127.1, 127.0, 123.2, 115.2, 62.6, 62.4, 52.1, 51.8, 46.5, 45.2, 31.8, 30.9, 19.7. LC-MS(ESI)=538.32[m / z],448.27(-Bn)

[0125] N-(1-benzylpiperidin-4-yl)-3-[6-(piperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 9d (LIT-TB007) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 110 mg, 0.276 mmol), piperazine 8d (2 equiv., 47.5 mg, 0.552 mmol), and EtN (2 equiv., 55.8 mg, 76.7 μL, 0.552 mmol) in EtOH (2.5 mL). The crude was evaporated and purified by silica gel chromatography (DCM / MeOH / EtN; 4 / 1 / 0 to 4 / 1 / 0.1) to give 9d (LIT-TB007) as a yellowish solid (m = 108 mg, yield = 87%). 1 H NMR (400 MHz, chloroform-d) δ 7.78 (d, J = 10.1 Hz, 1H),7.30-7.18(m,4H),6.89(d,J=10.1Hz,1H),6.61(d,J=8.3Hz,1H),3. 78-3.70(m,1H),3.52-3.48(m,4H),3.44(s,2H),3.33(t,J=7.3Hz,2H),2. 99-2.95(m,4H),2.84(t,J=7.2Hz,2H),2.74(d,J=11.7Hz,2H),2.05(t,J =11.3Hz,2H),1.80(dd,J=13.2,3.8Hz,2H),1.45(qd,J=11.2,3.5Hz,2H). 13 C NMR (101 MHz, chloroform-d) δ 171.1, 155.1, 148.8, 142.7, 138.4, 129.2, 128.3, 127.1, 124.5, 113.6, 63.1, 52.3, 47.1, 46.7, 45.6, 32.7, 32.0, 20.4. LC-MS (ES+APCI) [M+H] + =449.2

[0126] N-(1-benzylpiperidin-4-yl)-3-[6-(4-phenylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 9e (LIT-TB030) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equivalent, 38 mg, 0.0953 mmol), 1-phenylpiperazine 8e (2 equivalents, 31.9 mg, 30 μL, 0.191 mmol), and EtN (2 equivalents, 19.3 mg, 26.5 μL, 0.191 mmol) in EtOH (0.6 mL). The crude material was evaporated. A solution of (HO / MeOH; 9 / 1, 1 mL) was added to form a solid. The solid was sonicated and triturated in the presence of heptane, then filtered and washed with heptane to give the desired product. The product was salified and lyophilized to give 9e (LIT-TB030) as a beige solid (m=25.8 mg, yield=49%). 1 H NMR (400MHz, methanol-d4) δ7.89(d,J=10.1Hz,1H),7.37(d,J=10.2Hz,1H),7.33-7.22( m,7H),7.02(d,J=8.1Hz,2H),6.87(t,J=7.5Hz,1H),3.79-3.76(m,4H),3.66-3.60(m, 1H),3.50(s,2H),3.37-3.28(m,6H),2.83(d,J=11.8Hz,2H),2.76(t,J=7.7Hz,2H),2. 10(t,J=11.7Hz,2H),1.78(d,J=12.8Hz,2H),1.46(q,J=11.3,10.6Hz,2H),NH(not visible). 13 C NMR (101 MHz, methanol-d₄) δ 173.3, 156.8, 152.6, 150.1, 144.0, 138.2, 130.8, 130.2, 129.3, 128.5, 124.7, 121.5, 117.8, 116.7, 63.9, 53.2, 50.4, 47.9, 46.9, 33.3, 32.2, 21.2. LC-MS(ESI)[M+H] +=525.22

[0127] N-(1-benzylpiperidin-4-yl)-3-(6-(4-(pyrimidin-2-yl)piperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 9f, (LIT-TB004) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 100 mg, 0.25 mmol), 2-(1-piperazinyl)pyrimidine 8f (1 equiv., 41.2 mg, 35.5 μL, 0.25 mmol), and EtN (2 equiv., 50.7 mg, 70 μL, 0.50 mmol) in EtOH (1.2 mL). The reaction mixture was heated at 135 °C for 2 h. The crude was evaporated and purified by silica gel flash chromatography (EtOAc / MeOH / EtN:9 / 1 / 0.5), salified, triturated with anhydrous EtO, and lyophilized to give 9f (LIT-TB004) as a brown solid (m = 50 mg, yield = 3.5). 8%). LC-MS [M+H] + =529.2;551.2(M+Na)

[0128] 3-(6-([1,4'-bipiperidin]-1'-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(1-benzylpiperidin-4-yl)propanamide 9g, (LIT-TB003) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equivalent, 100 mg, 0.25 mmol), 4-piperidinopiperidine 8g (2 equivalents, 84.4 mg, 0.50 mmol), and EtN (2 equivalents, 50.7 mg, 70 μL, 0.50 mmol) in EtOH (1.2 mL). The reaction mixture was heated at 135 °C for 2 h. The crude was evaporated and purified by silica gel flash chromatography (EtOAc / MeOH / EtN:9 / 1 / 0.5), triturated with anhydrous EtO, salified and lyophilized to give 9g (LIT-TB003) as a brown solid (m = 100 mg, yield = 75%). LC-MS [M+H] + =531.4.

[0129] N-(1-benzylpiperidin-4-yl)-4-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)butanamide 10a (LIT-TB009) General procedure A for synthesizing LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-4-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)butanamide 7b (1 equivalent, 100 mg, 0.24 mmol), 1-methylpiperazine 8a (2 equivalents, 48.5 mg, 0.48 mmol), and EtN (2 equivalents, 49.0 mg, 67 μL, 0.48 mmol) in EtOH (1.1 mL). The reaction mixture was heated at 135 °C for 1.5 h. The crude was evaporated and purified by silica gel flash chromatography (EtOAc / MeOH / EtN:9 / 1 / 0.5), triturated with anhydrous EtO, salified, and lyophilized to give 10a (LIT-TB009) as a brown solid (m = 55 mg, yield = 48%). 1H NMR (400MHz, methanol-d4) δ7.86(d,1H,J=10.2Hz),7.50-7.42(m,2H),7.37-7.30(m,3H),7.29(d,1H,J=10.2Hz),3.80-3.6 0(m,5H),3.40-3.25(m,6H),2.99-3.10(m,5H),2.81(s,3H),2.22(t,2H,J=7.2Hz),2.10-1.90(m,4H),1.65-1.80(m2H). 13 C NMR (101 MHz, methanol-d₄) δ 174.7, 156.2, 150.6, 144.0, 132.4, 131.2, 130.6, 130.4, 125.5, 116.6, 61.4, 54.0, 52.7, 51.9, 44.7, 44.0, 36.0, 29.6, 24.4, 23.3. LC-MS [M+H] + =477.2

[0130] 3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(1-phenethylpiperidin-4-yl)propanamide 11a (LIT-TB011) General procedure A for the synthesis of LIT-TB001 analogs was followed using 3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(1-phenethylpiperidin-4-yl)propanamide 7c (1 equiv., 100 mg, 0.24 mmol), 1-methylpiperazine 8a (2 equiv., 48.5 mg, 0.48 mmol), and EtN (2 equiv., 49.0 mg, 67 μL, 0.48 mmol) in EtOH (1.1 mL). The reaction mixture was heated at 150 °C under microwave irradiation for 1.5 h. The crude material was evaporated and purified by silica gel flash chromatography (EtOAc / MeOH / Et 3N:9 / 1 / 0.5), triturated with anhydrous Et2O, salified, and lyophilized to give 10a (LIT-TB009) as a pale yellow solid (m=70 mg, yield=61%). 1H NMR (400MHz, methanol-d4) δ8.2(d,J=10.2Hz,1H),7.85(d,J=10.2Hz,1H),7. 34-7.07(m,5H),4.58-4.47(m,2H),3.89-3.77(m,1H),3.69-3.57(m,4H),3 .48(t,J=13.3Hz,2H),3.42-3.36(m,2H),3.35-3.22(m,4H),3.06-2.97(m ,4H),2.90(s,3H),2.85-2.81(m,2H),2.10-1.88(m,2H),1.82-1.69(m,2H) 13 C NMR (101 MHz, methanol-d4) 174.6, 156.7, 156.4, 137.5, 137.4, 130.0, 129.8, 128.3, 124.6, 118.5, 59.0, 53.7, 53.0, 45.8, 44.3, 43.6, 32.4, 31.5, 30.2, 20.8. LC-MS [M+H] + =477.2

[0131] N-(1-benzylpiperidin-4-yl)-2-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)acetamide 12a (LIT-TB008) General procedure A for the synthesis of LIT-TB001 analogs was followed using N-(1-benzylpiperidin-4-yl)-2-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)acetamide 7d (1 equivalent, 100 mg, 0.26 mmol), 1-methylpiperazine 8a (1.5 equivalents, 39.0 mg, 0.39 mmol), and EtN (2 equivalents, 52.6 mg, 72 μL, 0.52 mmol) in EtOH (0.75 mL). The reaction mixture was heated at 150° C. under microwave irradiation for 1.5 h. The crude was evaporated, purified by silica gel flash chromatography (DCM / MeOH / EtN:8 / 2 / 0.1), salified, and lyophilized to give 12a (LIT-TB008) as a beige solid (m = 70 mg, yield = 60%). 1H NMR (400MHz, methanol-d4) δ7.96(d,J=10.2Hz,1H),7.42-7.32(m,6H),4.40-4.29(m,2H),4.20(s,2H),4.05-3.98(m,2H),3.87-3.82(m,1H),3 .60-3.52(m,2H),3.43(d,J=12.4Hz,2H),3.30-3.25(m,2H),3.01(t,J=12.2Hz,2H),2.86(s,3H),2.12-2.04(m,2H),1.74(q,J=12.2Hz,2H). 13 C NMR (101 MHz, methanol-d4) δ 168.7, 160.1, 156.5, 142.3, 138.6, 132.4, 131.3, 130.4, 125.1, 117.6, 61.6, 53.7, 52.6, 46.3, 44.3, 43.6, 32.0, 30.0. LC-MS [M+H] + =449.2

[0132] Alternatively, compounds 9–14 can be prepared in a three-step sequence, as shown in Scheme 2. Condensation of hydrazinopyridazine 5 with cyclic anhydride 2 in dioxane at 120 °C afforded triazolopyridazinepropanoic acid (or homologue) 15 in one step. Peptide-type coupling of the above compounds 1 and 15 in the presence of isobutyl chloroformate afforded the aforementioned triazolo-pyridazine amides 7a–f. Finally, nucleophilic aromatic substitution with piperidine or piperazine derivatives 8a–g, as described in Example 1, afforded products of general formula 9–14.

[0133] [ka]

[0134] Conditions: a) succinic anhydride or glutaric anhydride, dioxane, 120°C, 12 hours; b) isobutyl chloroformate, DIEA, DCM, 25°C, 2 hours; c) 8a-g, Et3N, EtOH, 150°C, 1 hour 30 minutes.

[0135] Example 2: N-(1-benzylpiperidin-3-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 13a (m=0, m′=2, n=1, r=1) (LIT-TB055) Step 1: 3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanoic acid 15 Succinic anhydride (1.18 equiv., 500 mg, 3.46 mmol) was solubilized in dioxane (5 mL). 3-Chloro-6-hydrazinylpyridazine 5 (1.18 equiv., 420 mg, 0.566 mL, 4.07 mmol) was added, and the reaction mixture was heated for 2 h to give triazolo-pyridazinylpropanoic acid 15. The white precipitate was filtered and washed with EtO to give the title compound 15 (m = 437 mg, yield = 56%). 1 H NMR (400MHz, DMSO-d6) δ11.93(bs,1H),8.44(d,J=9.6Hz,1H),7.49(d,J=9.6Hz,1H),3.27(t,J=7.2Hz,2H),2.88(t,J=7.2Hz,2H). 13 C NMR (101MHz, DMSO-d6) δ173.5,149.2,149.0,143.3,127.5,122.9,30.2,19.4.

[0136] Step 2: N-(1-benzylpiperidin-3-yl)-3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 7e 3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanoic acid 15 (1.0 equiv., 119 mg, 0.52 mmol) was suspended in DCM (3 mL) followed by DIEA (2 equiv., 129.2 mg, 0.17 mL, 1.05 mmol). Isobutyl chloroformate (1.2 equiv., 86.1 mg, 82.2 μL, 0.63 mmol) in DCM (0.5 mL) was then added dropwise to the solution, and the resulting mixture was stirred at room temperature for 30 min. 1-Benzylpiperidin-3-amine (1 equiv., 100 mg, 0.52 mmol) was then introduced, and stirring was maintained for another 2 h. The volatiles were evaporated and then the crude was purified by silica gel column chromatography using DCM / MeOH:90 / 10 as the eluent to give the title compound 7e as a yellowish solid (m=50 mg, yield=24%). 1 H NMR (400MHz, methanol-d4) δ8.23(d,J=9.7Hz,1H),7.42(d,J=9.7Hz,1H),7.35-7.30(m ,4H),7.29-7.24(m,1H),3.94-3.85(m,1H),3.56(s,2H),3.43(t,J=7.5Hz,2H),2.84 J=7.5Hz,2H),273-2.66(m,1H),2.14(t,J=11.7Hz,1H),2.04-1.94(m,1H), 1.86-1.77(m,1H),1.76-1.68(m,1H),1.66-1.55(m,1H),1.33-1.22(m,1H). 13 C NMR (101 MHz, methanol-d4) δ 129.2, 127.9, 127.0, 125.8 ,123.3,62.6,57.5,52.8,45.9,31.5,29.5,22.9,19.6.

[0137] Step 3: N-(1-benzylpiperidin-3-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide (m=0, m'=2, n=1, r=1) Using general procedure A for synthesizing LIT-TB001 analogs, starting from N-(1-benzylpiperidin-3-yl)-3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 7e (1 equivalent, 50 mg, 0.12 mmol), 1-methylpiperazine 8a (2 equivalents, 25.1 mg, 27.8 μL, 0.25 mmol), and EtN (2 equivalents, 25.4 mg, 34.8 μL, 0.25 mmol) in EtOH (0.5 mL) at 135° C. for 1.5 h, the title compound 13a was obtained as a yellowish solid (m = 28.6 mg, yield = 43%) after salification and lyophilization. 1 H NMR (400MHz, methanol-d4) δ7.98(d,J=10.2Hz,1H),7.51-7.43(m,5H),7.41(d,J= 10.2Hz,1H),4.16(s,2H),4.06-3.96(m,1H),3.90-3.76(m,4H),3.36(t,J=7.3H z,2H),3.29-3.15(m,2H),3.10-3.00(m,4H),2.92-2.67(m,2H),2.81(t,J=12. 3Hz, 2H), 2.68 (s, 3H), 1.99-1.87 (m, 2H), 1.85-1.74 (m, 1H), 1.59-1.47 (m, 1H). 13 C NMR (101 MHz, methanol-d₄) δ 173.7, 156.5, 150.0, 144.0, 132.0, 130.6, 130.1, 125.1, 116.6, 62.4, 56.15, 54.6, 53.4, 45.9, 45.5, 44.9, 32.8, 29.0, 22.5, 20.9. LC-MS [M+H] + =462.28

[0138] Alternatively, compounds 9-14 could also be prepared by reductive amination of N-BOC-protected pyridazinotriazoles 17a-f in the presence of an appropriate phenylalkyl-aldehyde with the aid of sodium cyanoborohydride (Scheme 3). Compound 17 was readily accessible from the above carboxylic acid 15 by peptide-type coupling with the commercially available N-BOC-protected amino-piperidine derivative (or homologue) 16 using isobutyl chloroformate as the activating agent (Scheme 3).

[0139] [ka]

[0140] Conditions: a) 16, isobutyl chloroformate, DIEA, DCM, 25°C, 2 hours b) TFA, DCM, 1 hour; c) Ph (CH2) n -1CHO, NaBH3CN, DIEA, EtOH;c)8a~g, Et3N, EtOH, 135℃, 1 hour 30 minutes.

[0141] Example 3: N-(1-benzylazepan-4-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 14 (m=1, m′=2, n=1, r=1) (LIT-TB056) Step 1: tert-butyl 4-(3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide)azepane-1-carboxylate 17f (m=1, m'=2, r=1) 3-(6-Chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanoic acid 15 (1.0 equiv., 116.3 mg, 0.51 mmol) was suspended in DCM (4 ml) followed by DIEA (2 equiv., 134.7 mg, 898 μl, 1.04 mmol). Isobutyl chloroformate (1.2 equiv., 84.2 mg, 1.20 mL, 0.61 mmol) was dissolved in DCM (0.5 mL) and added dropwise to the previous solution, and the resulting mixture was stirred at room temperature for 30 min. tert-Butyl 4-aminoazepane-1-carboxylate (1 equiv., 110 mg, 0.51 mmol) was dissolved in DCM (0.5 mL) and added dropwise, and stirring was maintained for another 2 h. The volatiles were evaporated, and the crude was then purified by silica gel column chromatography using EtOAc / MeOH:80 / 20 as the eluent to give the title compound 17 as a yellowish oil (m = 129 mg, yield = 59%). 1 H NMR (400MHz, methanol-d4) δ8.12(d,J=9.7Hz,1H),7.31(d,J=9.6Hz,1H),3.69-3.59(m,1H),3. 49-3.38(m,1H),3.33(t,J=7.5Hz,2H),3.32-3.25(m,2H),3.17-3.06(m,1H),2.71(2.70)(t ,J=7.5Hz,2H),1.89-1.79(m,1H),1.78-1.67(m,2H),1.69-1.31(m,3H),1.37(1.36)(s,9H, cis-trans shape). 13 C NMR (101 MHz, methanol-d₄) δ 172.4, 157.3, 151.2, 150.9, 144.6, 127.3, 124.7, 81.0 (79.9), 51.2 (51.0), 47.4 (46.8), 44.0 (43.6), 35.7 (35.5), 34.2 (33.9), 32.9, 28.7, 25.6 (25.5), 21.0.

[0142] Step 2: N-(1-benzylazepan-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7f (m = 1, m' = 2, r = 1) To an ice-cold solution of tert-butyl 4-(3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamido)azepane-1-carboxylate 17f (1 equiv., 129 mg, 0.30 mmol) in DCM (1.5 mL) was added TFA (0.5 mL), and the resulting mixture was stirred for 2 h. The crude reaction was concentrated in vacuo with azeotropic removal of TFA with heptane. The compound was used in the reductive amination step without further purification. The crude was dissolved in MeOH (2 mL). Benzaldehyde (2.2 equiv., 71.2 mg, 68 μL) was added, followed by NaBHCN (3.6 equiv., 69 mg, 1.1 mmol). The resulting mixture was stirred at 25 °C overnight. The volatiles were evaporated, and the crude was taken up in EtOAc (25 mL). The organic phase was washed with brine, dried and concentrated in vacuo. The residue was purified by silica gel column chromatography using EtOAc:MeOH (90:10) as an eluent to give 2-(1-benzylpiperidin-4-yl)-4-phenylpyridazin-3(2H)-one as a yellow oil (m=92 mg, yield=71%). 1 H NMR (400MHz, methanol-d4) δ8.17(d,J=9.6Hz,1H),7.48-7.39(m,5H),7.35(d,J=9.6Hz,1H),4.21(s,2H),3.93-3.83(m,1H), 3.37(t,J=7.3Hz,2H),3.30-3.08(m,4H),2.77(t,J=7.3Hz,2H),2.07-1.96(m,2H),1.92-1.73(m,3H),1.63-1.50(m,1H). 13 C NMR (101 MHz, methanol-d₄) δ 172.9, 151.4, 150.9, 144.7, 132.1, 131.0, 130.4, 127.4, 127.0, 124.8, 62.3, 55.8, 51.5, 50.1, 33.8, 33.0, 30.4, 21.7, 21.0.

[0143] Step 3: N-(1-benzylazepan-4-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 14 Using the same procedure A described in Example 1 for synthesizing LIT-TB001 analogs, starting from N-(1-benzylazepan-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7f (1 equiv., 92 mg, 0.22 mmol), 1-methylpiperazine 8a (2 equiv., 40.2 mg, 44.6 μL, 0.40 mmol), and EtN (2 equiv., 45.2 mg, 62.1 μL, 0.2 mmol) in EtOH (0.5 ml), the title compound 14 was obtained as a yellowish solid after salification and lyophilization (m = 23.5 mg, yield = 11%). 1 H NMR (400MHz, methanol-d4) δ7.79(d,J=10.2Hz,1H),7.36-7.28(m,5H),7.25(d ,J=10.1Hz,1H),3.89(s,2H),3.87-3.79(m,1H),3.56(t,J=4.5Hz,4H),3.24 (t,J=7.4Hz,2H),2.99-2.75(m,4H),2.66(t,J=7.4Hz,2H),2.51(t,J=5.1Hz ,4H),2.28(s,3H),1.90-1.80(m,2H),1.79-1.59(m,3H),1.54-1.43(m,1H). 13 C NMR (101 MHz, methanol-d₄) δ 171.6, 155.3, 152.2, 142.6, 129.9, 128.5, 128.4, 123.3, 115.2, 61.4, 54.7, 53.9, 50.3, 48.7, 45.0, 44.6, 32.6, 31.7, 30.7, 21.7, 19.7. LC-MS[ESI]: 476.30(m / z)

[0144] General Procedure B The preparation of compounds of formula 20 bearing variously substituted piperidines on the propanamide chain may be carried out along various synthetic routes using conventional methods (Scheme 4). Starting from the readily available 6-chloro-triazolopyridazine N-BOC-protected piperidine 17a, SNAr reaction with 8aj afforded the corresponding 6-N-methylpiperazine 18a. Deprotection of the protecting BOC group and direct alkylation with an appropriate halogenoalkyl derivative (Method A, see Example 4) or reductive amination with an appropriate aldehyde in the presence of NaBH(OAc) (Method B, see Example 5) afforded examples of the present invention.

[0145] [ka]

[0146] Conditions: a) 8a, Et3N, EtOH, 135 °C, 1 hour 30 minutes; b) 4N HCl / dioxane; c) TFA, DCM, 2 hours; d) RX, K2CO3, DMF, argon, -5 °C (30 minutes) → room temperature (overnight); e) RCHO; NaBH(OAc)3, MeOH tert-Butyl 4-(3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamido)piperidine-1-carboxylate 17a Using the same procedure as described for the preparation of 17f, starting from 3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanoic acid 15a (1.0 equiv., 200 mg, 0.89 mmol) and 4-amino-1-Boc piperidine (1.0 equiv., 180 mg, 0.89 mmol, CAS number: 87120-72-7), the title compound was obtained as a beige solid (m = 234 mg, yield = 64%). 1H NMR(400MHz,DMSO-d6)δ8.43(d,J=9.7Hz,1H),7.95(d,J=8.0Hz,1H),7.48(d,J=9.7Hz,1H),3.81(d,J=14.3Hz,2H),3.75-3.65(m,1H) ),3.27(t,J=7.5Hz,2H),2.93-2.75(m,2H),2.68(t,J=7.5Hz,2H),1.68(dd,J=12.9Hz,J=4.1Hz,2H),1.39(s,9H),126-1.14(m,2H). 13 C NMR (100MHz, DMSO-d6) δ170.1,154.4,149.4,149.1,143.2,127.4,122.8,79.1,46.1,32.0,31.8,28.5,20.0.

[0147] tert-Butyl 4-(3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamido)piperidine-1-carboxylate 18a The use of general procedure A for synthesizing LIT-TB001 analogs was followed using tert-butyl 4-(3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamido)piperidine-1-carboxylate 17a (1 equiv., 50 mg, 0.12 mmol), 1-methyl-piperazine 8a (2 equiv., 16.4 mg, 19 μL, 0.191 mmol), and EtN (2 equiv., 24.75 mg, 34 μL, 0.24 mmol) in EtOH (0.8 mL). The crude material was evaporated and purified by reverse-phase chromatography (HO / MeOH) to give the title compound as a white solid (m = 45 mg, yield = 78%). 1H NMR (400MHz, methanol-d4) δ7.90(d,J=10.2Hz,1H),7.36(d,J=10.2Hz,1H),3.98( d,J=13.7Hz,2H),3.81(tt,J=10.8,4.1Hz,1H),3.68(t,J=5.2Hz,4H),3.36(dd, J=7.9,7.2Hz,2H),2.96-2.85(m,2H),2.78(t,J=7.5Hz,2H),2.62(t,J=5.1Hz, 4H), 2.38(s, 3H), 1.80(dd, J=13.1, 3.8Hz, 2H), 1.46(s, 9H), 1.37-1.25(m, 2H). 13 C NMR (101 MHz, methanol-d4) δ 173.2, 156.8, 156.4, 150.0, 144.0, 124.7, 116.6, 81.1, 55.4, 47.9, 46.46, 46.44, 46.1, 33.2, 32.6, 28.7, 21.1.

[0148] 3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(piperidin-4-yl)propanamide 19 (LIT-TB021) tert-Butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (67 mg, 0.14 mmol) was solubilized in DCM (0.7 mL). A solution of 4N NCl in dioxane was added (10 equiv., 1.42 mmol, 0.35 mL). ml) was added and the reaction mixture was stirred at room temperature for 30 min. The precipitate was collected, washed three times with dry EtO and dried (m=27 mg, yield=43%). 1H NMR (400MHz, methanol-d4) δ7.89(d,J=10.2Hz,1H),7.34(d,J=10.2Hz,1H),3.79-3.6 8(m,1H),3.66(t,J=5.1Hz,4H),3.34(t,J=7.6Hz,2H),3.03(dt,J=12.7Hz,J=4.1H z,2H),2.76(t,J=7.6Hz,2H),2.65(td,J=12.2Hz,J=2.8Hz,2H),2.60(t,J=5.1Hz, 4H),2.36(s,3H),1.81(dd,J=12.9Hz,J=3.8Hz,2H),1.37(qd,J=12.0Hz,J=6.0Hz). 13 C NMR (101 MHz, methanol-d4) δ 173.3, 156.9, 150.2, 144.1, 124.9, 116.8, 55.5, 48.0, 46.6, 46.3, 45.8, 33.3, 33.1, 21.3. LC-MS [M+H] + =372.24

[0149] Example 4: N-{1-[(4-methoxyphenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20a (LIT-TB017) tert-Butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (17.2 mg, 0.0364 mmol) was solubilized in DCM (0.3 mL). TFA (10 equiv., 41.5 mg, 27 μL, 0.364 mmol) was added, and the reaction mixture was stirred at room temperature for 2 h. The crude product was evaporated and then coevaporated twice with DCM / heptane. After drying, the crude product was solubilized in dry DMF under argon. K2CO3 (5 equiv., 25.2 mg, 0.182 mmol) was added, and the reaction mixture was stirred at -5 °C for 30 min. 1-(Bromomethyl)-4-methoxybenzene (1 equiv., 7.32 mg, 5.25 μL, 0.0364 mmol) was added, and the mixture was stirred at −5° C. for 0.5 h and then at room temperature overnight. Water (a few drops) was added, and the crude was directly purified by reverse-phase chromatography (HO / MeOH). The product was evaporated and diluted with MeOH. HCl (2 M) in EtO (excess) was added, and the reaction was stirred at room temperature for 1.5 h. The mixture was evaporated, diluted with water, and lyophilized. The title compound 20a was obtained as a yellowish solid (m=6.9 mg, yield=30%). 1 H NMR (400MHz, methanol-d4) δ7.89(d,J=10.2Hz,1H),7.35(d,J=10.2Hz,1H),7.24(d,J=8. 1Hz,2H),6.89(d,J=8.1Hz,2H),3.79(s,3H),3.68-3.60(m,5H),3.52(s,2H),3.36-3. 31(m,2H),2.88(d,J=11.6Hz,2H),2.76(t,J=7.7Hz,2H),2.61-2.58(m,4H),2.37(s,3 H),2.18(t,J=11.6Hz,2H),1.81(d,J=13.0Hz,2H),1.48(q,J=12.0Hz,2H),NH(not visible). 13 C NMR (126 MHz, methanol-d₄) δ 173.3, 160.8, 156.8, 150.1, 143.9, 132.2, 129.5, 124.7, 116.6, 114.8, 63.1, 55.7, 55.4, 53.0, 47.7, 46.4, 46.1, 33.2, 32.0, 21.2. LC-MS(ESI)[M+H] + =493.20

[0150] N-{1-[(3-chlorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20b (LIT-TB018) tert-Butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 14.9 mg, 0.0315 m General procedure B for the synthesis of 20a was followed using 2-chlorobenzyl bromide (1.1 equiv., 7.35 mg, 4.69 μL, 0.0347 mmol), 3-chlorobenzyl bromide (1.1 equiv., 7.35 mg, 4.69 μL, 0.0347 mmol), and KCO (5 equiv., 21.8 mg, 0.158 mmol). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20b as a yellowish solid (m = 9.4 mg, yield = 52%). 1 H NMR (400MHz, methanol-d4) δ7.89(d,J=10.1Hz,1H),7.39-7.22(m,5H),3.67-3.50(m,5H),3.50(s,2H),3.33(t,J=11.0Hz,2H),2.82(d,J=11 .8Hz,2H),2.76(t,J=7.6Hz,2H),2.61-2.58(m,4H),2.36(s,3H),2.12(t,J=11.8Hz,2H),1.80(d,J=12.9Hz,2H),1.47(q,J=11.9Hz,2H). 13 C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 141.3, 135.3, 130.8, 130.4, 128.9, 128.5, 124.7, 116.6, 63.2, 55.4, 53.3, 47.9, 46.4, 46.1, 33.2, 32.4, 21.2. LC-MS(ESI)[M+H] + =497.17

[0151] N-{1-[(2-chlorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20c (LIT-TB019) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 14.8 mg, 0.0313 mmol), 2-chlorobenzyl bromide (1.1 equiv., 7.08 mg, 4.47 μL, 0.0344 mmol), and KCO (5 equiv., 21.6 mg, 0.157 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20c as a yellowish solid (m = 11.2 mg, yield = 63%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.0Hz,1H),7.47(d,J=6.9Hz,1H),7.42(d,J=6.8Hz,1H),7.38-7.27(m,3H),3.83(s,2H),3.72-3.69(m,5H) ),3.35-3.31(m,2H),3.02(d,J=11.8Hz,2H),2.80-2.69(m,6H),2.49-2 .43(m,2H),2.45(s,3H),1.86(d,J=12.9Hz,2H),1.57(q,J=11.5Hz,2H. 13 C NMR (101 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 132.4, 130.5, 129.7, 127.9, 124.7, 116.5, 60.1, 55.4, 53.4, 47.9, 46.4, 46.1, 33.2, 32.5, 21.2. LC-MS(ESI)[M+H] + =497.16

[0152] N-{1-[(4-fluorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20d (LIT-TB020) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 16.3 mg, 0.0345 mmol), 4-fluorobenzyl chloride (1.1 equiv., 5.49 mg, 4.52 μL, 0.0379 mmol), and KCO (5 equiv., 23.8 mg, 0.172 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20d. was obtained as a yellowish solid (m=5.1 mg, yield=27%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.2Hz,1H),7.35-7.31(m,3H),7.04(t,J=8.6Hz,2H),3.67-3.62(m,5H),3.50(s,2H),3.35-3.30(m,2H),2.8 3(d,J=11.5Hz,2H),2.75(t,J=7.6Hz,2H),2.60-2.58(m,4H),2.35(s,3H) ),2.12(t,J=11.8Hz,2H),1.79(d,J=12.9Hz,2H),1.46(q,J=12.0Hz,2H). 13 C NMR (126 MHz, methanol-d₄) δ 173.2, 163.6 (d, J = 244.1 Hz), 156.8, 150.1, 143.9, 134.6 (d, J = 3.2 Hz), 132.5 (d, J = 8.0 Hz), 124.7, 116.6, 115.9 (d, J = 21.5 Hz), 63.0, 55.4, 53.2, 47.9, 46.4, 46.1, 33.2, 32.4, 21.2. 19 F NMR (376 MHz, methanol-d4) δ -117.5. LC-MS(ESI)[M+H] + =481.18

[0153] N-{1-[(2-fluorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20e (LIT-TB022) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 16.3 mg, 0.0345 mmol), 2-fluorobenzyl bromide (1.1 equiv., 7.17 mg, 4.58 μL, 0.0379 mmol), and KCO (5 equiv., 23.8 mg, 0.172 mmol) in DMF (0.3 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20e as a yellowish solid (m = 10.9 mg, yield = 57%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.1Hz,1H),7.42-7.27(m,3H),7.15(t,J= 7.6Hz,1H),7.08(t,J=9.4Hz,1H),3.67-3.65(m,5H),3.59(s,2H),3.35-3.31( m,2H),2.86(d,J=11.8Hz,2H),2.75(t,J=7.7Hz,2H),2.60-2.58(m,4H),2.36( s, 3H), 2.17 (t, J = 11.7Hz, 2H), 1.79 (d, J = 12.9Hz, 2H), 1.47 (q, J = 12.0Hz, 2H). 13 C NMR (126MHz, methanol-d4) δ173.2,162.9(d,J=245.2Hz),156.8,150.1,143.9,133.3(d,J=4.2Hz),130.6(d,J=8.3Hz),125.1 (d,J=3.6Hz),125.0,124.7,116.6,116.2(d,J=22.6Hz),56.0(d,J=1.9Hz),55.4,53.1,47.8,46.4,46.1,33.2,32.3,21.2. 19F NMR (376 MHz, methanol-d4) δ -119.35. LC-MS(ESI)[M+H] + =481.19

[0154] 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-[1-(1-phenylethyl)piperidin-4-yl]propanamide 20f (LIT-TB023) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 19.4 mg, 0.0411 mmol), (1-bromoethyl)benzene (1.1 equiv., 8.36 mg, 6.19 μL, 0.0452 mmol), and KCO (5 equiv., 28.4 mg, 0.205 mmol) in DMF (0.3 mL). The crude was evaporated and purified by reverse phase chromatography. Purification by chromatography (H2O / MeOH), salification, and lyophilization gave 20f as a yellowish solid (m=14.4 mg, yield=64%). 1 H NMR (400 MHz, methanol-d4) δ 7.88 (d, J = 10.0 Hz, 1H), 7.36-7.22 (m, 6H), 3.66-3.64 (m, 4H), 3.57 (t, J = 11.4 Hz, 1H), 3.48 (q, J = 6.7 Hz, 1H), 3.35-3.31 (m, 2H), 3.07 (d, J = 11 .6Hz,1H),2.80-2.72(m,3H),2.60-2.57(m,4H),2.35(s,3H),2.08(dt,J=34.5,11 .9Hz,2H),1.78(dd,J=34.3,13.0Hz,2H),1.56-1.38(m,2H),1.41(d,J=6.7Hz,3H). 13C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 143.4, 129.4, 129.0, 128.5, 124.7, 116.6, 66.4, 55.4, 51.0, 50.4, 47.9, 46.4, 46.1, 33.2, 32.4, 21.2, 19.7. LC-MS(ESI)[M+H] + =477.21

[0155] N-{1-[(2-methylphenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20g (LIT-TB024) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 17.7 mg, 0.0375 mmol), 2-methylbenzyl bromide (1.1 equiv., 7.62 mg, 5.52 μL, 0.0412 mmol), and KCO (5 equiv., 25.9 mg, 0.187 mmol) in DMF (0.3 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20g as a yellowish solid (m = 13.3 mg, yield = 65%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.2Hz,1H),7.33(d,J=10.1Hz,1H),7.23-7. 21(m,1H),7.14-7.10(m,3H),3.67-3.64(m,5H),3.49(s,2H),3.35-3.31(m,2H), 2.85(d,J=11.5Hz,2H),2.75(t,J=7.6Hz,2H),2.61-2.58(m,4H),2.36(s,3H),2. 35(s,3H),2.15(t,J=11.8Hz,2H),1.78(d,J=12.8Hz,2H),1.45(q,J=11.9Hz,2H). 13C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 138.7, 137.0, 131.4, 131.2, 128.4, 126.6, 124.7, 116.6, 61.4, 55.4, 53.5, 48.0, 46.4, 46.1, 33.2, 32.5, 21.2, 19.5. LC-MS(ESI)[M+H] + =477.24

[0156] 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-[1-(pyridin-4-ylmethyl)piperidin-4-yl]propanamide 20h (LIT-TB025) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 20.5 mg, 0.0434 mmol), 4-(chloromethyl)pyridine hydrochloride (1.1 equiv., 7.83 mg, 0.0477 mmol), and KCO (5 equiv., 30 mg, 0.217 mmol) in DMF (0.3 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20h as a yellowish solid (m = 13.9 mg, yield = 56%). 1 H NMR (500MHz, methanol-d4) δ8.49-8.43(m,2H),7.88(d,J=10.2Hz,1H),7.43-7. 40(m,2H),7.33(d,J=10.2Hz,1H),3.68-3.60(m,5H),3.56(s,2H),3.35-3.31 (m,2H),2.80(d,J=11.9Hz,2H),2.75(t,J=7.6Hz,2H),2.61-3.58(m,4H),2.3 6(s,3H),2.14(td,J=11.8,2.5Hz,2H),1.83-1.76(m,2H),1.53-1.44(m,2H). 13C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.3, 150.1, 150.0, 144.0, 125.8, 124.7, 116.6, 62.5, 55.4, 53.5, 47.9, 46.4, 46.1, 33.2, 32.5, 21.2. LC-MS(ESI)[M+H] + =464.18

[0157] N-{1-[(3,4-dichlorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20i (LIT-TB026) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 19.2 mg, 0.0406 mmol), 3,4-dichlorobenzyl chloride (1.1 equiv., 8.74 mg, 6.2 μL, 0.0447 mmol), and KCO (5 equiv., 28.1 mg, 0.203 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20i as a yellowish solid (m = 15.6 mg, yield = 64%). 1 H NMR (500MHz, methanol-d4) δ7.88(d,J=10.1Hz,1H),7.50(d,J=2.0Hz,1H),7.45(d,J=8.2H) z,1H),7.33(d,J=10.2Hz,1H),7.24(dd,J=8.2,2.0Hz,1H),3.69-3.58(m,5H),3.47(s,2 H),3.35-3.31(m,2H),2.83-2.77(m,2H),2.75(t,J=7.6Hz,2H),2.60-2.57(m,4H),2.3 5(s,3H),2.11(td,J=11.8,2.6Hz,2H),1.79(dd,J=12.9,3.9Hz,2H),1.53-1.41(m,2H). 13C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 140.1, 133.2, 132.3, 132.0, 131.4, 130.2, 124.7, 116.6, 62.5, 55.4, 53.3, 47.9, 46.4, 46.1, 33.2, 32.4, 21.2. LC-MS(ESI)[M+H] + =531.11

[0158] N-(1-benzoylpiperidin-4-yl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide hydrochloride 20j (LIT-TB027) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 20.2 mg, 0.0427 mmol), benzoyl chloride (1.1 equiv., 6.61 mg, 5.46 μL, 0.047 mmol), and KCO (5 equiv., 29.5 mg, 0.214 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20j as a yellowish solid (m = 8.2 mg, yield = 32%). 1 H NMR (400 MHz, methanol-d4) δ 7.91 (d, J = 10.2 Hz, 1H), 7.48-7.44 (m, 3H), 7.41-7.35 (m, 3H), 4.47 (d, J = 13.4 Hz 1H), 3.93 (tt, J = 10.5, 4.2 Hz, 1H) ,3.77-3.63(d,J=5.3Hz,5H),3.36(t,J=7.4Hz,2H),3.23-3.02(m,2H),2.83-2.76(m,6H),2.50(s,3H),2.00-1.73(m,2H),1.51-1.30(m,2H). 13C NMR (126 MHz, methanol-d₄) δ 173.3, 172.5, 156.8, 150.0, 144.0, 137.0, 131.1, 129.8, 127.8, 124.7, 116.6, 55.4, 47.8, 46.4, 46.1, 42.1, 33.2, 32.2, 21.1. LC-MS(ESI)[M+H] + =477.17

[0159] N-{1-[(4-chlorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20kJ (LIT-TB028) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 19.8 mg, 0.0419 mmol), 4-chlorobenzyl bromide (1.1 equiv., 9.47 mg, 0.0461 mmol) (1.1 equiv., 6.61 mg, 5.46 μL, 0.047 mmol), and KCO (5 equiv., 29 mg, 0.209 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20k as a yellowish solid (m = 10.8 mg, yield = 45%). 1 H NMR (500MHz, methanol-d4) δ7.88(d,J=10.1Hz,1H),7.33(d,J=10.2Hz,1H),7. 31-7.29(m,4H),3.69-3.58(m,5H),3.48(s,2H),3.35-3.31(m,2H),2.81(d ,J=11.8Hz,2H),2.74(t,J=7.5Hz,2H),2.60-2.57(m,4H),2.35(s,3H),2.1 0(td,J=11.8,2.5Hz,2H),1.78(dd,J=13.5,3.7Hz,2H),1.54-1.41(m,2H). 13C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 137.5, 134.2, 132.2, 129.4, 124.7, 116.6, 63.0, 55.4, 53.2, 47.9, 46.4, 46.1, 33.2, 32.4, 21.2. LC-MS(ESI)[M+H] + =497.16

[0160] N-[1-(cyclohexylmethyl)piperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20l (LIT-TB031) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 19.8 mg, 0.0419 mmol), KI (1 equiv., 7.73 mg, 0.0466 mmol), and cyclohexylmethyl 4-methylbenzene-1-sulfonate (1.1 equiv., 13.7 mg, 0.0512 mmol), and KCO (5 equiv., 32.2 mg, 0.233 mmol) in DMF (0.3 ml) at 85 °C overnight. The crude was evaporated, purified by reverse phase chromatography (H2O / MeOH), salified and lyophilized to give 20l as a yellowish solid (m=4.1 mg, yield=16%). 1 H NMR (500MHz, methanol-d4) δ7.92(d,J=10.2Hz,1H),7.38(d,J=10.2Hz,1H),3.74-3.61(m,5H),3.38(t,J=7.6Hz,2H),2. 87(d,J=11.8Hz,2H),2.80(t,J=7.6Hz,2H),2.64-2.62(m,4H),2.40(s,3H),2.18(d,J=6.8Hz,2H),2.06(t,J=11.6Hz, 2H), 1.84-1.70(m, 7H), 1.35-1.21(m, 3H), 1.37-1.17(m, 3H), 0.98-0.90(m, 2H).13 C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 144.0, 124.7, 116.6, 66.9, 55.4, 54.0, 48.1, 46.4, 46.1, 36.4, 33.2, 33.2, 32.3, 27.7, 27.2, 21.2. LC-MS(ESI)[M+H] + =469.24

[0161] N-{1-[(5-methyl-1H-imidazol-4-yl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20mM (LIT-TB032) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 22 mg, 0.0466 mmol), KI (1 equiv., 7.73 mg, 0.0466 mmol), and 4-(chloromethyl)-5-methyl-1H-imidazole (1.1 equiv., 6.69 mg, 0.0512 mmol), and KCO (5 equiv., 32.2 mg, 0.233 mmol) in DMF (0.5 ml) at 85 °C for 5 h. The crude was evaporated, purified by reverse phase chromatography (H2O / MeOH), salified and lyophilized to give 20m as a yellowish solid (m = 7.8 mg, yield = 30%). 1 H NMR (500MHz, methanol-d4) δ7.95(d,J=10.2Hz,1H),7.57(s,1H),7.40(d,J=10.2H z,1H),3.74-3.72(m,4H),3.70-3.63(m,1H),3.55(s,2H),3.42-3.39(m,2H),2 .93(d,J=11.6Hz,2H),2.82(t,J=7.6Hz,2H),2.67-2.65(m,4H),2.43(s,3H),2 .27(s,3H),2.26-2.21(m,2H),1.87(dd,J=13.2,3.8Hz,2H),1.57-1.50(m,2H).13 C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 150.1, 143.9, 134.8, 124.7, 116.6, 55.4, 52.9, 47.8, 46.4, 46.1, 33.2, 32.3, 21.2. LC-MS(ESI)[M+H] + =467.21

[0162] N-{1-[(2,4-difluorophenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20n (LIT-TB040) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 26 mg, 0.055 mmol), 2,4-difluorobenzyl bromide (1.1 equiv., 12.5 mg, 7.78 μL, 0.0605 mmol), and KCO (5 equiv., 38 mg, 0.275 mmol) in DMF (0.3 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20n as a yellowish solid (m = 25.6 mg, yield = 81%). 1 H NMR (500MHz, methanol-d4) δ7.93(d,J=10.2Hz,1H),7.49-7.44(m,1H),7.38(d,J= 10.2Hz,1H),7.01-6.95(m,2H),3.72-3.70(m,4H),3.70-3.63(m,1H),3.60(s,2) H),3.40-3.37(m,2H),2.88(d,J=11.9Hz,2H),2.80(t,J=7.6Hz,2H),2.65-2.6 3(m,4H),2.41(s,3H),2.23-2.18(m,2H),1.88-1.80(m,2H),1.56-1.48(m,2H). 13 C NMR (126 MHz, methanol-d4) δ 173.2, 163.9 (dd, J = 247.0, 12. 0Hz),162.9(dd,J=248.0,12.5Hz),156.8,150.1,143.9,134.3(dd,J=9.6,5.9Hz),124.7,121.5(dd,J=14.7,3.7Hz) ,116.5,112.1(dd,J=21.6,3.8Hz),104.4(dd,J=26.8,25.7Hz),55.5,55.4,53.0,47.8,46.5,46.1,33.2,32.4,21.2. 19 F NMR (376 MHz, methanol-d4) δ -113.2, -114.8. LC-MS(ESI)[M+H] + =499.21

[0163] N-{1-[(4-fluoro-2-phenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 20o (LIT-TB044) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 24.7 mg, 0.0523 mmol), 1-(bromomethyl)-4-fluoro-2-methylbenzene (1.1 equiv., 11.7 mg, 8.02 μL, 0.0575 mmol), and KCO (5 equiv., 36.1 mg, 0.261 mmol) in DMF (0.4 mL). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20o as a yellowish solid (m = 14.8 mg, yield = 50%). 1H NMR (500MHz, methanol-d4) δ7.87(d,J=10.2Hz,1H),7.33(d,J=10.2Hz,1H),7.21(dd,J=8.4,6.0Hz,1 H),6.88(dd,J=9.9,2.7Hz,1H),6.83(td,J=8.5,2.8Hz,1H),3.67-3.60(m,5H),3.42(s,2H),3.35- 3.31(m,2H),2.80(d,J=11.6Hz,2H),2.75(t,J=7.6Hz,2H),2.58(t,J=5.1Hz,4H),2.35(s,3H),2.3 5(s,3H),2.09(td,J=11.7,2.5Hz,2H),1.76(dd,J=13.5,4.0Hz,2H),1.42(qd,J=11.6,3.8Hz,2H). 13 C NMR (126MHz, methanol-d4) δ173.2,163.3(d,J=243.4Hz),156.8,150.1,143.9,141.4(d,J=7.7Hz),133.4(d,J=2.9Hz),132.8(d, J=8.3Hz),124.7,117.7(d,J=21.0Hz),116.6,112.9(d,J=20.9Hz),60.8,55.4,53.4,48.1,46.4,46.1,33.2,32.6,21.2,19.5. 19 F NMR (471 MHz, methanol-d4) δ -118.5. LC-MS(ESI)[M+H] + =495.28

[0164] N-{1-[(4-methoxy-2-methylphenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide dihydrochloride 20p (LIT-TB045) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 25 mg, 0.0529 mmol), 1-(bromomethyl)-4-methoxy-2-methylbenzene (1.2 equiv., 13.7 mg, 0.0635 mmol), and KCO (5 equiv., 36.6 mg, 0.265 mmol) in DMF (0.4 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20p as a yellowish solid (m = 11.5 mg, yield = 38%). 1 H NMR (500 MHz, methanol-d4) δ 7.97 (d, J = 10.1 Hz, 1H), 7.42 (d, J = 10.2 Hz, 1H), 7.21 (d, J = 8.4 Hz, 1H) H),6.82(d,J=2.6Hz,1H),6.78(dd,J=8.3,2.7Hz,1H),3.86(s,3H),3.78-3.70(m,5H),3.50(s,2H),3.46-3.41(m,2H),2.92(d,J=11.8Hz,2H ),2.85(t,J=7.6Hz,2H),2.69(t,J=5.1Hz,4H),2.46(s,3H),2.43(s,3H),2.22-2.16(m,2H),1.90-1.84(m,2H),1.53(qd,J=11.5,3.7Hz,2H). 13 C NMR (126 MHz, methanol-d4) δ 173.2, 160.3, 156.8, 150.1, 143.9, 140.1, 132.5, 129.4, 124.7, 116.9, 116.6, 111.6, 60.9, 55.6, 55.4, 53.4, 48.2, 46.4, 46.1, 33.3, 32.6, 21.2, 19.7. LC-MS(ESI)[M+H] + =507.31

[0165] N-{1-[(2-fluoro-4-methoxyphenyl)methyl]piperidin-4-yl}-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide dihydrochloride 20q (LIT-TB046) General procedure B for the synthesis of 20a was followed using tert-butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (1 equiv., 26 mg, 0.055 mmol), 1-(bromomethyl)-2-fluoro-4-methoxybenzene (1.4 equiv., 16.9 mg, 0.077 mmol), and KCO (5 equiv., 38 mg, 0.275 mmol) in DMF (0.4 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 20q as a yellowish solid (m = 16.5 mg, yield = 51%). 1 H NMR (400MHz, methanol-d4) δ7.89(dd,J=10.3,2.9Hz,1H),7.34(dd,J=10.5,2.8Hz,1H),7.27(dd ,J=10.0,7.5Hz,1H),6.73(d,J=8.6Hz,1H),6.68(d,J=12.1Hz,1H),3.79(s,3H),3.69-3.57(m ,5H),3.52(s,2H),3.36-3.33(m,2H),2.85(d,J=11.6Hz,2H),2.75(t,J=7.8Hz,2H),2.62-2.5 8(m,4H),2.36(s,3H),2.14(t,J=11.8Hz,2H),1.79(d,J=12.8Hz,2H),1.46(q,J=12.1Hz,2H). 13C NMR (101MHz, methanol-d4) δ173.2,163.5(d,J=244.9Hz),162.2(d,J=11.2Hz),156.8,150.1,143.9,133.9(d,J=6.2Hz),124.7,116 .56,116.55(d,J=15.6Hz),110.9(d,J=2.9Hz),102.2(d,J=26.6Hz),56.1,55.6,55.4,52.8,47.8,46.4,46.1,33.2,32.3,21.2. 19 F NMR (376 MHz, methanol-d4) δ -116.9. LC-MS(ESI)[M+H] + =511.26

[0166] Example 5: 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-[1-(1,3-oxazol-4-ylmethyl)piperidin-4-yl]propanamide 20r (LIT-TB050) tert-Butyl 4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 18a (18.6 mg, 0.039 mmol) was solubilized in DCM (0.3 mL). TFA (10 equiv., 41.5 mg, 27 μL, 0.364 mmol) was added and the reaction mixture was stirred at room temperature for 2 h. The crude product was evaporated and then co-evaporated twice with DCM / heptane. After drying, the crude product was taken up in a saturated solution of KCO and extracted twice with DCM. The organic phase was dried over NaSO, filtered and evaporated. The crude product (13 mg, 0 0.035 mmol) and was used in the next step without further purification.

[0167] 3-[6-(4-Methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-(piperidin-4-yl)propanamide 19 (1 equiv., 13 mg, 0.0349 mmol) was solubilized in dry MeOH (0.5 mL) under argon. 1,3-Oxazole-4-carbaldehyde (2 equiv., 6.78 mg, 0.0698 mmol) was added, and the reaction mixture was stirred at room temperature for 10 minutes. NaBH(OAc)3 (2 equiv., 15.6 mg, 0.0698 mmol) was solubilized in dry MeOH (0.5 mL) and added to the reaction mixture. The reaction was stirred at room temperature for 40 hours. Water was added and the crude was directly purified by reverse phase chromatography (H2O / MeOH), salified with aqueous HCl (2 M) and lyophilized to give 20r as a white solid (m = 3.7 mg, yield = 20%). 1 H NMR (500MHz, methanol-d4) δ8.16(d,J=0.9Hz,1H),7.90(d,J=10.2Hz,1H),7.86(d,J=0. 9Hz,1H),7.36(d,J=10.2Hz,1H),3.69-3.65(m,4H),3.65-3.58(m,1H),3.52(s,2H), 3.37-3.33(m,2H),2.90(d,J=11.8Hz,2H),2.76(t,J=7.6Hz,2H),2.60(t,J=5.1Hz,4 H),2.37(s,3H),2.22-2.12(m,2H),1.81(dd,J=13.4,3.8Hz,2H),1.52-1.44(m,2H). 13 C NMR (126 MHz, methanol-d₄) δ 173.2, 156.8, 153.4, 150.1, 144.0, 139.0, 137.2, 124.7, 116.6, 55.4, 53.8, 53.1, 47.8, 46.4, 46.1, 33.2, 32.3, 21.2. LC-MS(ESI)[M+H] + =454.24

[0168] General Procedure C In general procedure C, diacylation of hydrazino-pyridazine 5 followed by cyclization of 22 under acidic conditions afforded the ethyl propionate triazolopyridazine 23 (Scheme 5). Reaction with secondary amines afforded triazolopyridazines 24 with various amine substitutions at the 6-position. Hydrolysis of the carboxylic acid ester and coupling to primary amine 25 afforded the final analogs 26 with another point of diversity on the six-membered aliphatic ring (Scheme 5).

[0169] [ka]

[0170] Conditions: a) 21, Na2SO4, DIEA, DMF, 48 hours, room temperature; b) AcOH, 135 °C, overnight; c) NR1R2, Et3N, EtOH, reflux overnight; d) LiOH, THF / H2O, 1 hour, room temperature; e) HATU, NEt3, DMF, overnight Ethyl 4-[2-(6-chloropyridazin-3-yl)-2-(4-ethoxy-4-oxo-butanoyl)hydrazino]-4-oxo-butanoate 22 3-Chloro-6-hydrazinylpyridazine 5 (1 equiv., 600 mg, 4.15 mmol) was solubilized in dry DMF (10 mL). NaSO (50 mg) and DIEA (2.2 equiv., 1180 mg, 1.51 mL, 9.13 mmol) were added, and the reaction mixture was cooled to 0 °C and stirred for 15 min. Ethyl succinyl chloride 21 (1.2 equiv., 819 mg, 0.708 mL, 4.98 mmol) was then added dropwise, and the reaction mixture was stirred at room temperature over the weekend. The DMF was evaporated, and the crude material was purified by silica gel chromatography (EtOAc / heptane, 1 / 1, 5 / 1 to 1 / 0) to give 22 as a white solid (m = 1 g, yield = 61%). 1 H NMR (400MHz, methanol-d4) δ7.51(d,J=9.4Hz,1H),7.15(d,J=9.4Hz,1H),4.15(qd,J=7.1,6.0Hz,4H),2.72-2.54(m,8H),1.26(td,J=7.1,1.9Hz,6H). 13C NMR (101 MHz, methanol-d₄) δ 174.4, 174.3, 174.1, 173.3, 161.6, 149.6, 131.3, 118.2, 61.8, 61.7, 30.0, 29.9, 29.32, 29.28, 14.48, 14.46.

[0171] Ethyl 3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanoate 23 4-[2-(6-chloropyridazin-3-yl)-2-(4-ethoxy-4-oxo- Ethyl [butanoyl]hydrazino-4-oxobutanoate 22 (1 equiv., 960 mg, 3.52 mmol) was solubilized in acetic acid (38.6 equiv., 8157 mg, 7.78 mL, 135 mmol), and the reaction was heated at 135 °C overnight. The crude was cooled to room temperature and evaporated. The crude was purified by silica gel chromatography (heptane / EtOAc; 1 / 1, 1 / 5 to 0 / 1) to give compound 23 as a white solid (m = 586 mg, yield = 96%). 1 H NMR (400MHz, methanol-d4) δ8.26(d,J=9.7Hz,1H),7.45(d,J=9.7Hz,1H),4.16(q,J =7.1Hz,2H),3.47(t,J=7.3Hz,2H),3.04(t,J=7.3Hz,2H),1.26(t,J=7.1Hz,3H). 13 C NMR (101 MHz, methanol-d4) δ 173.5, 151.2, 150.6, 144.6, 127.3, 124.6, 61.9, 31.2, 20.4, 14.4.

[0172] Ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24a Ethyl 3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanoate 23 (1 equiv., 586 mg, 2.3 mmol) was solubilized in EtOH (2.5 mL). 1-Methylpiperazine (2 equiv., 460 mg, 0.51 mL, 4.6 mmol) and EtN (2 equiv., 465 mg, 0.64 mL, 4.6 mmol) were added, and the reaction was heated to reflux overnight. The crude product was cooled to room temperature and evaporated. The crude product was purified by silica gel chromatography (EtOAc / MeOH / EtN; 9 / 1 / 0.5 to 7 / 1 / 0.5) to give 24a as a pale yellow solid (m = 728 mg, yield = 99%). 1 H NMR (400MHz, methanol-d4) δ7.97(d,J=10.2Hz,1H),7.39(d,J=10.2Hz,1H),4.12(q,J=7.1Hz,2H),3.90-3.85( m,4H),3.36(t,J=7.4Hz,2H),3.24-3.19(m,4H),2.97(t,J=7.4Hz,2H),2.80(s,3H),1.21(t,J=7.1Hz,3H). 13 C NMR (101 MHz, methanol-d4) δ 173.7, 156.4, 149.9, 144.0, 125.3, 116.5, 61.9, 54.3, 31.3, 20.5, 14.4.

[0173] Example 6: 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-(1-methyl-piperidin-4-yl)propanamide 26a (LIT-TB016) Ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24a (1 equiv., 30 mg, 0.0942 mmol) was diluted with a mixture of THF / HO (1 / 1; 6 mL). LiOH (5 equiv., 19.8 mg, 0.471 mmol) was added, and the reaction mixture was stirred at room temperature for 1 h. The crude product was acidified with HCl (2 M), evaporated, and diluted with dry DMF (0.5 mL). HATU (2.5 equiv., 89.6 mg, 0.236 mmol) and EtN (2.5 equiv., 23.8 mg, 32.7 μL, 0.236 mmol) were added, and the reaction mixture was stirred at room temperature for 15 min. 1-Methylpiperidin-4-amine 25a (1.2 equiv., 13.3 mg, 14.6 μL, 0.113 mmol) was then added, and the reaction mixture was stirred at room temperature overnight. The crude was directly purified by reverse-phase chromatography (MeOH / HO) to give a sticky oil. A second purification run gave the desired compound. The product was evaporated and diluted with MeOH. 2 M HCl in EtO (excess) was added, and the reaction was stirred at room temperature for 1.5 h. The mixture was evaporated, diluted with water, and lyophilized to give 26a as a white solid (m = 2.9 mg, yield = 7%). 1 H NMR (500 MHz, methanol-d4) δ 7.88 (d, J = 10.2 Hz, 1H), 7.34 (d, J = 10.2 Hz, 1H), 3.68-3.63 (m, 5H), 3.33(t,J=7.5Hz,2H),2.93-2.85(m,2H),2.76(t,J=7.5,2H),2.61-2.57(m,4H),2.3 6(s,3H),2.34(s,3H),2.25(t,J=11.8Hz,2H),1.88-1.83(m,2H),1.54-1.47(m,2H). 13 C NMR (126 MHz, methanol-d₄) δ 173.4, 156.8, 150.1, 144.0, 124.7, 116.6, 68.9, 55.4, 46.4, 46.1, 45.8, 33.1, 31.9, 26.5, 21.1. LC-MS(ESI)[M+H] + =387.17

[0174] N-(1-benzyl-4-piperidyl)-3-[6-[2-(dimethylamino)ethylamino]-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 26b (LIT-TB051) Ethyl 3-[6-[2-(dimethylamino)ethylamino]-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24b (1 equiv., 18 mg, 0.0588 mmol) was diluted in a mixture of THF / HO (1 / 1; 6 mL). LiOH (5 equiv., 12.3 mg, 8.62 μL, 0.294 mmol) was added, and the reaction mixture was stirred at room temperature for 1 h. The crude product was acidified with HCl (2 M), evaporated, and diluted with dry DMF (0.5 mL). Sulfate was added to the mixture and stirred for 5 min. HATU (1.2 equiv., 26.8 mg, 0.0705 mmol) and EtN (2.5 equiv., 14.9 mg, 20.4 μL, 0.147 mmol) were added, and the reaction mixture was stirred at room temperature for 15 min. 4-Amino-1-benzylpiperidine 25b (1.5 equiv., 16.8 mg, 18 μg, 0.0881 mmol) was then added, and the reaction mixture was stirred at 60° C. for 3 h. The crude was filtered over a pad of Celite and washed with MeOH. The filtrate was evaporated, purified by reverse-phase chromatography (MeOH / HO), salified using aqueous HCl (2 M), and lyophilized to give 26b as a white solid (m=14.3 mg, yield=46%). 1 H NMR (400MHz, methanol-d4) δ7.74(d,J=9.9Hz,1H),7.34-7.24(m,5H),6.81(d,J=9.9Hz,1H),3.68-3.60(m,1H),3.58-3.53(m,4H),3.35-3 .29(m,2H),2.87(d,J=11.7Hz,2H),2.78-2.73(m,4H),2.41(s,6H),2.18-2.12(m,2H),1.81(dd,J=13.4,3.9Hz,2H),1.55-1.42(m,2H). 13C NMR (101 MHz, methanol-d4) δ 173.2, 155.8, 149.9, 144.3, 138.2, 130.8, 129.4, 128.6, 124.0, 119.4, 63.9, 58.2, 53.2, 47.8, 45.4, 39.7, 33.2, 32.2, 21.1. LC-MS (ESI) [M+H] + =451.26

[0175] N-(1-benzyl-2-oxopiperidin-4-yl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 26c (LIT-TB033) General procedure C for the synthesis of 26a was followed using ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 11a (1.5 equiv., 54.9 mg, 0.173 mmol) and LiOH (5 equiv., 24.1 mg, 0.575 mmol) in THF / HO (1 / 1; 6 mL). The crude was treated with HATU (1.2 equiv., 52.5 mg, 0.138 mmol), EtN (5 equiv., 58.2 mg, 80 μL, 0.575 mmol), and 4-amino-1-benzylpiperidin-2-one 25c (1 equiv., 23.5 mg, 0.115 mmol) in dry DMF (1 mL).

[0176] The crude material was directly purified by reverse phase chromatography (MeOH / H2O). Semi-preparative chromatography (MeOH / H2O + 0.05% HCl) was performed to isolate the product. The compound was salified and lyophilized to give 26c as a yellowish solid (m=8.5 mg, yield=14%). 1H NMR (500MHz, methanol-d4) δ7.78(d,J=10.2Hz,1H),7.26-7.20(m,3H),7.17-7.14(m,3H),4 .56-4.41(m,2H),4.00(tdd,J=9.1,5.7,3.3Hz,1H),3.57-3.55(m,4H),3.27-3.16(m,4H ),2.68(t,J=7.5Hz,2H),2.62(ddd,J=17.4,5.7,1.6Hz,1H),2.51-2.49(m,4H),2.26(s, 3H),2.23(dd,J=17.9,9.2Hz,1H),1.89(ddt,J=13.0,4.8,3.1Hz,1H),1.68-1.59(m,1H). 13 C NMR (126 MHz, methanol-d₄) δ 173.6, 170.5, 156.8, 150.0, 144.0, 138.1, 129.7, 129.0, 128.6, 124.7, 116.6, 55.4, 50.9, 46.4, 46.1, 45.5, 45.1, 38.5, 33.0, 29.2, 21.0. LC-MS(ESI)[M+H] + =477.19

[0177] N-(4-Benzylcyclohexyl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 26d (LIT-TB034). General procedure C for the synthesis of 26a was followed using ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24a (1.5 equiv., 50.2 mg, 0.158 mmol) and LiOH (5 equiv., 22.1 mg, 0.526 mmol) in THF / HO (1 / 1; 6 mL). The crude material in dry DMF (1 mL) was treated with HATU (1.2 equiv., 48 mg, 0.126 mmol), EtN (5 equiv., 53.2 mg, 73 μL, 0.526 mmol), and 4-benzylcyclohexane-1-amine 25d (1 equiv., 19.9 mg, 0.105 mmol). The crude material was directly purified by reverse-phase chromatography (MeOH / HO). The product was isolated by semi-preparative chromatography (MeOH / HO+0.05% HCl). The compound was salified and lyophilized to give 26d as a pale yellowish solid (m=11.3 mg, yield=22%). 1 H NMR (500MHz, methanol-d4) δ8.26(d,J=9.7Hz,1H),7.93(d,J=9.8Hz,1H),7.22-7.19(m,2H),7.14-7. 07(m,3H),4.59(d,J=14.2Hz,2H),3.66(d,J=11.5Hz,2H),3.60-3.48(m,3H),3.43(t,J=6.5Hz,2H ),3.35-3.28(m,2H),2.96(s,3H),2.85-2.82(m,2H),2.46(d,J=7.0Hz,2H),1.81(d,J=9.3Hz,2H) ,1.70(d,J=11.0Hz,2H),1.47(ddt,J=11.3,7.7,3.8Hz,1H),1.19-1.11(m,2H),1.07-0.96(m,2H). 13 C NMR (126 MHz, methanol-d₄) δ 172.1, 157.5, 150.5, 142.1, 141.0, 130.1, 129.2, 126.8, 122.6, 122.6, 53.8, 50.2, 44.4, 44.1, 43.7, 40.3, 33.5, 32.7, 31.9, 20.7. LC-MS(ESI)[M+H] + =462.20

[0178] 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-(1-phenylpiperidin-4-yl)propanamide 26e (LIT-TB035) Ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24a (1.5 equiv., 60 mg, 0.188 mmol) and LiOH (1.5 equiv., 6 General procedure C for the synthesis of 26a was followed using 26b (1.0 mg, 0.188 mmol). The crude was treated with HATU (1.2 eq., 57.3 mg, 0.151 mmol), EtN (5 eq., 63.6 mg, 87.3 μL, 0.628 mmol), and 1-phenylpiperidin-4-amine 25e (1 eq., 22.1 mg, 0.126 mmol; CAS 63921-23-3) in dry DMF (1 ml). The crude was directly purified by reverse-phase chromatography (MeOH / HO). The compound was salified and lyophilized to give 26e as a pale yellowish solid (m = 20.9 mg, yield = 34%). 1 H NMR (500MHz, methanol-d4) δ7.88(d,J=10.1Hz,1H),7.34(d,J=10.2Hz,1H),7.23-7. 17(m,2H),6.99-6.94(m,2H),6.81(tt,J=7.3,1.1Hz,1H),3.77(tt,J=10.8,4.2Hz ,1H),3.69-3.63(m,4H),3.61-3.56(m,2H),3.35(t,J=7.6Hz,2H),2.82-2.74(m, 4H), 2.59(t,J=5.1Hz,4H),2.35(s,3H),1.92-1.88(m,2H),1.61-1.53(m,2H),NH. 13 C NMR (126 MHz, methanol-d4) δ 173.3, 156.8, 152.8, 150.1, 144.0, 130.0, 124.7, 121.1, 118.2, 116.6, 55.4, 50.2, 48.0, 46.4, 46.1, 33.2, 32.5, 21.2. LC-MS(ESI)[M+H] + =449.17

[0179] General Procedure D for the Preparation of 3-Fluoro-4-aminopiperidine Analogues of LIT-TB001

[0180] [ka]

[0181] Conditions: a) TFA, DCM, 2 h, RT; b) RX, K2CO3, DMF, argon, -5 °C (30 min) → RT (overnight). β-Fluoropiperidine analogs 27a–d were obtained by peptide-type coupling of enantiomerically pure 4-amino-3-fluoropiperidine to ethyl 3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanoate 24a according to general procedure C (compound 23 → compound 26).

[0182] tert-Butyl (3S,4R)-3-fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 27a 1 H NMR (500 MHz, methanol-d4) δ 7.90 (d, J = 10.2 Hz ,1H),7.36(d,J=10.2Hz,1H),4.64(d,J=48.9Hz,1H),4.35(s,1H),4.14(d,J=12.6Hz,1 H),4.00(dddd,J=30.8,12.3,4.9,2.2Hz,1H),3.67(dd,J=6.2,4.1Hz,4H),3.39-3.34( m,2H),2.83(t,J=7.6Hz,2H),2.61(t,J=5.1Hz,4H),2.38(s,3H),1.74(qd,J=12.7,4.5 Hz, 1H), 1.62 (ddd, J=10.1, 5.2, 2.6Hz, 1H), 1.46 (s, 9H), 1.35-1.29 (m, 2H), NH (not visible). 13C NMR (126 MHz, methanol-d₄) δ 173.5, 156.9, 156.8, 150.0, 144.0, 124.7, 116.6, 88.5 (d, J = 177.3 Hz), 81.4, 55.4, 50.1 (d, J = 18.9 Hz), 46.4, 46.1, 33.0, 32.9, 28.6, 23.7, 21.1, 14.4. 19 F NMR (471 MHz, methanol-d4) δ -205.7.

[0183] Example 7: N-[(3S,4R)-1-benzyl-3-fluoropiperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 28a (LIT-TB047) (3S,4R)-3-Fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate tert-butyl 27a (1 equiv., 30.4 mg, 0.062 mmol) was solubilized in DCM (0.7 mL). TFA (10 equiv., 70.7 mg, 46 μL, 0.62 mmol) was added, and the reaction mixture was stirred at room temperature for 2 h. The crude product was evaporated and then coevaporated with DCM / heptane (3×). After drying, the crude product was solubilized in dry DMF under argon. K2CO3 (5 equiv., 42.8 mg, 0.31 mmol) was added, and the reaction mixture was stirred at −5° C. for 30 min. Benzyl bromide (1.1 equiv., 11.7 mg, 8.15 μL, 0.0682 mmol) was added, and the mixture was stirred at −5° C. for 0.5 h and then at room temperature overnight. Water (a few drops) was added, and the crude material was directly purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give the title compound 28a as a yellowish solid (m=18.8 mg, yield=55%). 1H NMR (400 MHz, methanol-d4) δ 7.88 (d, J = 10.2 Hz, 1H), 7.37-7.22 (m, 6H), 4.61 (d, J = 49.3 Hz, 1H), 3.84 (dd, J = 30.4, 12.2 Hz, 1H), 3.65 (t, J = 4.8 Hz, 4H), 3.63-3.48 (m, 2H), 3.37-3.31 (m, 2H),3.11(t,J=11.8Hz,1H),2.90(d,J=11.7Hz,1H),2.85-2.77(m,2H),2.59(t,J=4.8Hz, 4H),2.36(s,3H),2.29-2.15(m,2H),1.89(q,J=13.0,12.5Hz,1H),1.63(d,J=13.0Hz,1H). 13 C NMR (101 MHz, methanol-d₄) δ 173.5, 156.8, 150.0, 144.0, 138.3, 130.5, 129.3, 128.4, 124.7, 116.6, 89.0 (d, J = 177.1 Hz), 63.3, 56.3 (d, J = 18.9 Hz), 55.4, 52.7, 50.0 (d, J = 18.5 Hz), 46.4, 46.1, 32.9, 27.0, 21.1. 19 F NMR (376 MHz, methanol-d4) δ -201.6. LC-MS(ESI)[M+H] + =481.25

[0184] N-[(3S,4S)-1-benzyl-3-fluoropiperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 28b (LIT-TB048) tert-Butyl (3S,4S)-3-fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 27b (1 equiv., 26 mg, 0.053 mmol), benzyl bromide (1.1 equiv., 9.97 mg, 6.9 mmol) in DMF (0.5 ml). General procedure D for the synthesis of 28a was followed using HCl (7 μL, 0.0583 mmol), and KCO (5 equiv., 36.6 mg, 0.265 mmol). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 28b as a yellowish solid (m = 13.0 mg, yield = 44%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.3Hz,1H),7.35-7.25(m,6H),4.46-4.21 (m,1H),3.88-3.75(m,1H),3.65(t,J=4.9Hz,4H),3.61-3.53(m,2H),3.37-3.33 (m,2H),3.10(dd,J=11.0,5.7Hz,1H),2.82-2.76(m,3H),2.59(t,J=4.9Hz,4H), 2.36(s,3H),2.16-2.06(m,2H),1.89(d,J=12.5Hz,1H),1.46(q,J=11.7Hz,1H). 13 C NMR (101 MHz, methanol-d₄) δ 173.9, 156.8, 150.0, 144.0, 138.7, 130.4, 129.4, 128.5, 124.7, 116.6, 90.6 (d, J = 177.8 Hz), 63.2, 57.1 (d, J = 25.0 Hz), 55.4, 52.6 (d, J = 18.4 Hz), 52.4, 46.4, 46.1, 33.3, 30.4 (d, J = 6.9 Hz), 21.1. 19 F NMR (376 MHz, methanol-d4) δ -189.7. LC-MS(ESI)[M+H] + =481.25

[0185] N-[(3R,4R)-1-benzyl-3-fluoropiperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 28c (LIT-TB049) General procedure D for the synthesis of 28a was followed using tert-butyl (3R,4R)-3-fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 17c (1 equiv., 22.4 mg, 0.0457 mmol), benzyl bromide (1.1 equiv., 8.59 mg, 6.01 μL, 0.0502 mmol), and KCO (5 equiv., 31.6 mg, 0.228 mmol) in DMF (0.5 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 28c as a yellowish solid (m = 13.4 mg, yield = 54%). 1 H NMR (500 MHz, methanol-d4) δ 7.88 (d, J = 10.1 Hz, 1H), 7.36-7.25 (m, 6H), 4.34 (dtd, J = 49.7, 9.4, 4.7 Hz, 1H), 3.80 (tdd, J = 11.2, 9.2, 5.0 Hz, 1H), 3.68-3.64 (m, 4H), 3.61-3.53 (m, 2H), 3.38-3.64 (m, 3H). .34(m,2H),3.13-3.06(m,1H),2.82-2.75(m,3H),2.59(t,J=5.1Hz,4H),2.36(s,3H),2.16- 2.08(m,2H),1.89(dtt,J=13.6,5.8,3.0Hz,1H),1.46(dtdd,J=12.9,11.7,4.2,1.0Hz,1H),. 13 C NMR (126MHz, methanol-d4) δ173.9,156.8,150.0,144.0,138.6,130.4,129.4,128.5,124.7,116.6,90.6(d,J=17 7.9Hz),63.2,57.1(d,J=25.0Hz),55.4,52.6(d,J=18.5Hz),52.4,46.4,46.1,33.3,30.4(d,J=6.8Hz),21.1. 19 F NMR (471 MHz, methanol-d4) δ -189.7. LC-MS(ESI)[M+H] + =481.26

[0186] N-[(3R,4S)-1-benzyl-3-fluoropiperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 18d (LIT-TB054) (3R,4S)-3-fluoro-4-{3-[6-(4-methyl- General procedure D for the synthesis of 28a was followed using tert-butyl {ethylpiperazin-1-yl}-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 17d (1 equiv., 24 mg, 0.0489 mmol), (1.1 equiv., 9.2 mg, 6.44 μL, 0.0538 mmol), and KCO (5 equiv., 33.8 mg, 0.245 mmol). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 28d as a yellowish solid (m = 13.4 mg, yield = 49%). 1 H NMR (400 MHz, methanol-d4) δ 7.88 (d, J = 10.2 Hz, 1H), 7.36-7.24 (m, 6H), 4.61 (ddd, J = 49.3, 3.8, 2.1 Hz, 1H), 3.84 (dddd, J = 30.2, 12.3, 5.0, 2.5 Hz, 1H), 3.66 (t, J = 5.1 Hz, 4H), 3.55 (dd, J = 42.3, 13.0 Hz,2H),3.37-3.33(m,2H),3.15-3.08(m,1H),2.93-2.88(m,1H),2.82(t,J=7.6Hz,2H),2.59(t ,J=5.1Hz,4H),2.36(s,3H),2.31-2.14(m,2H),1.94-1.84(m,1H),1.63(dd,J=13.0,3.9Hz,1H). 13C NMR (101 MHz, methanol-d₄) δ 173.54, 156.78, 150.02, 143.95, 138.28, 130.55, 129.31, 128.43, 124.71, 116.57, 89.02 (d, J = 177.1 Hz), 63.26, 56.29 (d, J = 19.0 Hz), 55.39, 52.73, 50.02 (d, J = 18.5 Hz), 46.43, 46.11, 32.94, 27.04 (d, J = 1.7 Hz), 21.11. 19 F NMR (376 MHz, methanol-d4) δ -201.62. LC-MS(ESI)[M+H] + =481.23

[0187] N-[(3S,4S)-3-Fluoro-1-[(4-methoxyphenyl)methyl]piperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 29b (LIT-TB052) General procedure D for the synthesis of 28a was followed using tert-butyl (3S,4S)-3-fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 27b (1 equiv., 34 mg, 0.0693 mmol), 4-methoxybenzyl chloride (1.1 equiv., 12.2 mg, 10.5 μL, 0.0762 mmol), and KCO (5 equiv., 47.9 mg, 0.347 mmol) in DMF (0.7 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 29b as a white solid (m = 15.2 mg, yield = 58%). 1H NMR (400MHz, methanol-d4) δ7.88(d,J=10.2Hz,1H),7.34(d,J=10.2Hz,1H),7.24-7.19(m,2H),6.90-6.85(m ,2H),4.33(dtd,J=49.7,9.4,4.7Hz,1H),3.84-3.73(m,1H),3.78(s,3H),3.66(t,J=5.1Hz,4H),3.55-3. 47(m,2H),3.37-3.33(m,2H),3.11-3.06(m,1H),2.80(t,J=7.7Hz,2H),2.80-2.74(m,1H),2.59(t,J=5.1 Hz,4H),2.36(s,3H),2.12-2.05(m,2H),1.89(dtd,J=10.7,5.4,2.8Hz,1H),1.45(qd,J=12.0,3.9Hz,1H). 13 C NMR (101 MHz, methanol-d4) δ 173.89, 160.6, 156.8, 150.0, 144.0, 131.6, 130.4, 124.7, 116.6, 114.7, 90.7 (d, J = 177.8 Hz), 62.6, 57.0 (d, J = 24.9 Hz), 55.7, 55.4, 52.6 (d, J = 18.4 Hz), 52.3, 46.4, 4 6.1,33.3,30.4(d,J=7.0Hz),21.1. 19 F NMR (376 MHz, methanol-d4) δ -189.7. LC-MS(ESI)[M+H] + =511.27

[0188] N-[(3R,4R)-3-fluoro-1-[(4-methoxyphenyl)methyl]piperidin-4-yl]-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 29c (LIT-TB053) General procedure D for the synthesis of 28a was followed using tert-butyl (3R,4R)-3-fluoro-4-{3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide}piperidine-1-carboxylate 27c (1 equiv., 48.3 mg, 0.0985 mmol), 4-methoxybenzyl chloride (1.1 equiv., 17.3 mg, 15 μL, 0.108 mmol), and KCO (5 equiv., 68 mg, 0.492 mmol) in DMF (0.7 ml). The crude was evaporated, purified by reverse-phase chromatography (HO / MeOH), salified, and lyophilized to give 29c as a white solid (m = 17.3 mg, yield = 66%). 1 H NMR (400MHz, methanol-d4) δ7.88(d,J=10.2Hz,1H),7.34(d,J=10.2Hz,1H),7.24-7.19(m,2H),6.90-6.85(m ,2H),4.33(dtd,J=49.7,9.4,4.7Hz,1H),3.84-3.74(m,1H),3.79(s,3H),3.66(t,J=5.1Hz,4H),3.55-3. 47(m,2H),3.37-3.33(m,2H),3.12-3.06(m,1H),2.80(t,J=7.7Hz,2H),2.80-2.74(m,1H),2.59(t,J=5.1 Hz,4H),2.36(s,3H),2.12-2.05(m,2H),1.89(dtd,J=10.7,5.4,2.8Hz,1H),1.46(qd,J=12.0,3.9Hz,1H). 13 C NMR (101 MHz, methanol-d₄) δ 173.9, 160.6, 156.8, 150.0, 144.0, 131.6, 130.4, 124.7, 116.6, 114.7, 90.7 (d, J = 177.8 Hz), 62.6, 57.0 (d, J = 25.0 Hz), 55.7, 55.4, 52.6 (d, J = 18.4 Hz), 52.3, 46.4, 46.1, 33.3, 30.4 (d, J = 6.9 Hz), 21.1. 19 F NMR (376 MHz, methanol-d4) δ -189.7. LC-MS(ESI)[M+H] + =511.25

[0189] Preparation of triazolopyridines Alternatively, the carbaisostere of compound 9a (LIT-TB001) was prepared as reported in Scheme 7. Starting from the known hydrazine-bromopyridine derivative 35, reaction with propanoic acid 4a in the presence of isobutyl chloroformate gave hydrazide 36, which was subsequently cyclized to triazolopyridine 37 under Mitsunobu conditions in the presence of TMSN3. Final compound 38 was obtained under Buchwald cross-coupling reaction conditions.

[0190] [ka]

[0191] Conditions: NH2-NH2, 100°C, See Synthesis, 47(20), 3169-3178; 2015; b) 4a, isobutyl chloroformate, DIEA, THF, 25°C, 12 hours; c) DIAD, PPh3, TMSN3, THF, 12 hours; d) Pd(OAc)2, Binap, Cs2CO3, dioxane, 105°C, 12 hours.

[0192] Example 8: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-a]pyridin-3-yl)propanamide 38 (LIT-TB006) Step 1: N-(1-benzylpiperidin-4-yl)-4-(2-(5-bromopyridin-2-yl)hydrazinyl)-4-oxobutanamide 36 4-((1-benzylpiperidin-4-yl)amino)-4-oxobutanoic acid 4a (1.0 equiv., 300 mg, 1.56 mmol) was suspended in THF (6 mL) followed by NMM (1.2 equiv., 193.7 mg, 0.21 mL). Isobutyl chloroformate (0.5 g, 0.49 mL) was then added dropwise to the solution, and the resulting mixture was stirred at room temperature for 30 min. 5-Bromo-2-hydrazinylpyridine (1 equiv., 300 mg, 1.59 mmol) was then added, and stirring was maintained for another 1 h. The volatiles were evaporated, and the crude was dissolved in EtOAc (30 mL). The organic phase was washed once with 1 N NaCO (15 mL), water (15 mL), brine (20 mL), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was then purified by silica gel column chromatography using a gradient of 0% to 3% NEt3 in EtOAc:MeOH 9:1 to afford the title compound as a white solid (212 mg, 29%). 1 H NMR(400MHz,CDCl3)δ5.62(s,1H),8.11(s,1H),7.50(d,1H,J=8.0Hz),7.29-7 .20(m,5H);6.96(s,1H),6.54(d,1H,J=8.0Hz),5.93(d,1H,J=4.0Hz),3.73-3. 65(m,1H),3.45(s,2H),2.76(d,2H,J=4.0Hz),2.49(dd,2H,J=8.0Hz,J=4.0Hz) ,2.04(t,2H,J=12.0Hz),1.79(d,2H,J=12Hz),1.40(dq,2H,J=12Hz,J=4.0Hz). 13 C NMR(101MHz,CDCl3)δ172.5,171.3,158.1,148.7,140.5,12 9.3, 128.4, 127.3, 110.9, 108.3, 63.1, 52.3, 46.9, 32.1, 31.4, 29.7.

[0193] Step 2: N-(1-benzylpiperidin-4-yl)-3-(6-bromo-[1,2,4]triazolo[4,3-a]pyridin-3-yl)propanamide 37 A solution of DIAD (109.8 g, 107.7 μL, 2.5 equiv.) and TMS-N3 (62.56 mg, 0.54 mmol, 72.08 μL) in THF (0.4 mL) was slowly added to a solution of triphenylphosphine (142.4 g, 0.53 mmol, 2.5 equiv.), N-(1-benzylpiperidin-4-yl)-4-(2-(5-bromopyridin-2-yl)hydrazinyl)-4-oxobutanamide (100 mg, 0.21 mmol) in THF (1.2 mL), and the resulting cloudy mixture was stirred at room temperature overnight. Silica gel was added to the mixture, and the volatiles were evaporated. Flash chromatography of the crude product using a gradient of 0–3% EtN in 9:1 EtOAc-MeOH afforded the title compound as a pale yellow solid (m = 53.2 mg, yield = 55%). 1 H NMR (400MHz, methanol-d4) δ8.68(s,1H),7.62(d,1H,J=8.0Hz),7.48(d,1H,J=8.0Hz),7.33-7.25(m,5H),3.67-3.61(m,1H),3.65 (s,2H),2.90(d,2H,J=12.0Hz),2.79(t,2H,J=8.0Hz),2.24(t,1H,J=12.0Hz),1.80(m,2H),2.26(dq,2H,J=12.0Hz,J=4.0Hz). 13 C NMR (101 MHz, methanol-d₄) δ 173.1, 149.6, 148.3, 137.2, 133.1, 130.9, 129.4, 128.8, 125.3, 116.9, 109.8, 63.6, 53.0, 47.5, 33.6, 31.8, 21.1.

[0194] Step 3: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-a]pyridin-3-yl)propanamide 38 (LIT-TB006) To a microwave vial (oven-dried and under argon) was added N-(1-benzylpiperidin-4-yl)-3-(6-bromo-[1,2,4]triazolo[4,3-a]pyridin-3-yl)propanamide 37 (100 mg, 0.23 mmol, 1 equiv.), 1-methylpiperazine (22.64 mg, 25 μL, 0.23 mmol), CsCO (147.3 mg, 0.45 mmol, 2 equiv.), Pd(OAc) (1.02 mg, 2 mol%), and Binap (8.45 mg, 6 mol%), followed by dioxane (1.05 mL). The vial was capped appropriately, and the mixing vessel was evacuated and backfilled with argon (the process was repeated three times) and heated at 105 °C overnight. After cooling to room temperature, silica gel was added, and the resulting mixture was evaporated to dryness. Flash chromatography of the crude material using EtOAc / MeOH / Et3N 8:2:0.3 as eluent gave the title compound (m=40 mg, yield=38%). LC-MS(ESI)[M+H] + =462, 2979

[0195] Preparation of imidazopyridines The invention also provides a process for preparing imidazopyridine derivatives of general formula 44. An exemplary general synthetic method is provided in Scheme 8. A three-component Michael-type (3CC) reaction involving bromo-imidazopyridine, Meldrum's acid, and formaldehyde afforded the corresponding 3-imidazo[1,2-a]pyridin-3-ylpropionic acid using known procedures (Non-Patent Document 18). The reaction was carried out in the presence of a catalytic amount of L-proline to give the corresponding "Michael-type" Yonemitsu adduct 41, which was first converted to the stable ester 42 by ethanolysis and copper-catalyzed decarboxylation, and then to the corresponding amide 43 after successive alkaline hydrolysis and classical peptide coupling reactions. Finally, a Buchwald-type cross-coupling reaction afforded the target compound 44. (LIT-TB013) was obtained.

[0196] [ka]

[0197] Conditions: a) L-proline 5 mol%, MeCN, 50 °C, 10 h; b) Cu, pyridine-EtOH 10:1, reflux 3 h; c) KOH, EtOH-H2O, 50 °C, 10 h 1N HCl (pH = 6); d) 1, BOP, NMM, DCM, 12 h; e) Pd(OAc)2, Binap, Cs2CO3, dioxane, 105 °C, 12 h.

[0198] Example 9: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)imidazo[1,2-a]pyridin-3-yl)propanamide 44 (LIT-TB013) Step 1: Ethyl 3-(6-bromoimidazo[1,2-a]pyridin-3-yl)propanoate 42 6-Bromoimidazo[1,2-a]pyridine (1.50 g, 7.61 mmol, 1 equiv.), Meldrum's acid (1 equiv., 1.10 g, 7.61 mmol), paraformaldehyde (1 equiv., 228.6 mg, 7.61 mmol), and L-proline (43.8 mg, 5 mol%) were suspended in acetonitrile (29.23 mL), and the reaction mixture was stirred overnight at 50 °C under a nitrogen atmosphere. The precipitated product was collected by filtration and washed thoroughly with diethyl ether. The solid was dried (m = 1.83 g, 5.18 mmol, yield = 68%). The resulting compound 41 (1 equivalent, 1.50 g, 4.25 mmol) was dissolved in pyridine / EtOH (10:1 v / v, 5.5 mL), copper powder (12.75 mg, 0.20 mmol) was added, and the mixture was refluxed for 3 h. The solvent was removed under reduced pressure. Flash chromatography of the crude using EtOAc as the eluent gave the title compound 42 (m = 500 mg, yield = 40%). 1H NMR(400MHz,CDCl3)δ8.04(d,1H ,J=1.2Hz),7.43(d,1H,J=9.2Hz),7.36(s,1H),7.15(dd,1H,J=9.2Hz,J=1.2Hz),4.09( q,2H,J=7.2Hz),3.10(t,2H,J=15.2Hz),2.72(t,2H,J=14.8Hz),1.19(t,2H,J=7.2Hz). 13 C NMR(101MHz,CDCl3)δ172.5,151.6,131.8,126.9,123.2,123.1118.7, 112.6, 107.1, 60.9, 32.0, 19.4, 14.2.

[0199] Step 2: N-(1-benzylpiperidin-4-yl)-3-(6-bromoimidazo[1,2-a]pyridin-3-yl)propanamide 43 Ethyl 3-(6-bromoimidazo[1,2-a]pyridin-3-yl)propanoate 42 (1 equiv., 500 mg, 1.68 mmol) was dissolved in EtOH (10 mL) and then treated with potassium hydroxide (2 equiv., 189 mg, 3.36 mmol in 1 mL of HO) at 0 °C. The resulting mixture was stirred at ambient temperature for 1 h. The volatiles were evaporated, and the crude was dissolved in HO (20 mL) and extracted with EtOAc (15 mL). The organic solvent was removed, and the remaining aqueous solution was acidified with 1 N HCl until a pH of approximately 4 was reached. The resulting solid was filtered and dried under reduced pressure to give 3-(6-bromoimidazo[1,2-a]pyridin-3-yl)propanoic acid (m = 340 mg, yield = 75%).

[0200] The resulting acid (200 mg, 0.74 mmol, 1 equiv.) and BOP (349.5 mg, 0.74 mmol) were suspended in DCM (5.0 mL). NMM (112.8 mL, 122 μL, 1.11 mmol, 1.5 equiv.) was added, and the reaction mixture was stirred at room temperature for 15 min. 1-Benzylpiperidin-4-amine (141.5 mg, 0.74 mmol, 1 equiv.) was then added, and the reaction mixture was stirred at room temperature overnight (20 h). MeOH and silica were added, and the crude product was evaporated. The compound adsorbed on silica was then purified by silica gel chromatography (eluent MeOH / AcOEt 8 / 2) to give the title compound 43 as a yellow solid (m = 379 mg, yield = 93%).

[0201] Step 3: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)imidazo[1,2-a]yridazi-3-yl)propanamide 44 (LIT-TB013). In a microwave vial (oven-dried and under argon) was added N-(1-benzylpiperidin-4-yl)-3-(6-bromoimidazo[1,2-a])iridad-3-yl)propanamide 43 (1 equiv., 50 mg, 0.11 mmol), methylpiperazine (12.5 mg, 13.8 μL, 0.12 mmol), CsCO (2 equiv., 73.8 mg, 0.23 mmol), Pd(OAc) (0.8 mg, 3 mol%), and Binap (4.2 mg, 6 mol%), followed by dioxane (1.0 mL). The vial was capped appropriately, and the mixing vessel was evacuated and backfilled with argon (the process was repeated three times) and heated at 105 °C overnight. After cooling to room temperature, silica gel was added, and the resulting mixture was evaporated to dryness. Initial flash chromatography of the crude material using 8:2:0.3 EtOAc / MeOH / EtN followed by reverse C18 flash chromatography (10-100% MeOH in HO + 0.05% HCl) gave the title compound 44 (m = 7 mg, yield = 13%). LC-MS [M+H] + =461.2

[0202] Preparation of imidazopyridazines The previous Michael-type (3CC) reaction using Meldrum's acid and formaldehyde can be extended to imidazopyridazine derivatives (Scheme 9). This reaction in the presence of an electron-donating group (OMe) at the 6-position of the imidazopyridine moiety (cpd 46) allowed the formation of the corresponding propionic acid 47. Chlorination using POCl3, followed by peptide coupling with 1, followed by demethylation in the presence of LiCl and p-toluenesulfonic acid, afforded 6-chloroimidazo-pyridazine amide 49. Coupling of 49 with various heterocyclic secondary amines 8 under basic conditions as previously described provided the final compounds of formula 50.

[0203] [ka]

[0204] Conditions: a) MeONa, MeOH, 18 h; a) L-proline 5 mol%, MeCN, 50 °C, 36 h; b LiCl, pTsOH hydrate, DMF, 150 °C, 16 h; c) POCl3, catalyzed DMF, 150 °C, 16 h; d) 1, BOP, NMM, DCM, 12 h; e) EtOH, μ-wave, 150 °C for 2 h.

[0205] Example 10: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)imidazo[1,2-b]pyridazin-3-yl)propanamide 50 (LIT-TB014) Step 1: 6-Methoxyimidazo[1,2-b]pyridazine 46 Sodium methoxide (7.35 equiv., 7.76 g, 143.6 mmol) was added to a solution of 6-chloroimidazo[1,2-bb]pyridazine (3.0 g, 19.54 mmol) in anhydrous methanol (8 ml) at ambient temperature, and the reaction mixture was stirred for 18 hours. The volatiles were removed by evaporation, and the yellow oily residue was dissolved in dichloromethane (100 ml). The solution was washed with water (5 x 100 ml) until the aqueous washings were neutral. The organic solution was dried (MgSO4), and the solvent was removed. The title compound was obtained as a white solid (m = 8.87 g, yield = 91%). 1 H NMR (400MHz, DMSO-d6) δ7.36(d,J=9.3Hz,1H),6.85(d,J=9.3Hz,1H),6.61(s,1H). 13 C NMR (101MHz, CDCl3) δ160.2,137.3,132.4,127.3,116.8,112.1,54.4.

[0206] Step 2: 3-(6-Methoxyimidazo[1,2-b]pyridazin-3-yl)propanoic acid 47 6-Methoxyimidazo[1,2-b]pyridazine (1 equivalent, 1.0 g, 6.7 mmol), Meldrum's acid (1 equivalent, 0.97 g, 6.70 mmol), paraformaldehyde ( 1 equivalent, 201.3 mg, 6.70 mmol), and L-proline (38.6 mg, 5 mol%) were suspended in acetonitrile (30 mL), and the reaction mixture was stirred under a nitrogen atmosphere at 50° C. for 36 h. The precipitated product was collected by filtration, washed thoroughly with diethyl ether, and dried to give the title compound as a white solid (m=1.0 g, yield=67%). 1 H NMR (400MHz, DMSO-d6) δ12.71-12.01(bs,1H),7.96(d,J=9.6Hz,1H),7.43(s,1H,J=9.6Hz),6.81(d,J=9.6Hz,1H),3.97(s,3H). 13 C NMR (101MHz, CDCl3) δ173.5,159.5,136.5,129.9,127.6,127.5,110.3,54.3,31.1,18.8.

[0207] Step 3: 3-(6-hydroxyimidazo[1,2-b]pyridazin-3-yl)propanoic acid 48 The resulting acid (1 equiv., 920 mg, 4.16 mmol) was suspended in DMF (11.5 mL). LiCl (5 equiv., 881.6 mg, 20.8 mmol) was added, followed by pTsOH hydrate (5 equiv., 3.95 g, 20.79 mmol), and the resulting mixture was heated at 150° C. overnight under a nitrogen atmosphere. The DMF was evaporated, and the crude material was suspended in water. The precipitated product was collected by filtration, washed thoroughly with diethyl ether, and dried to give the title compound 48 (m=600 mg, yield=70%). 1 H NMR(400MHz,DMSO-d6)δ12.71-11.68(bs,1H),7.96(d,J=9.6Hz ,1H),7.43(s,1H,J=9.6Hz),6.83(d,J=9.6Hz,1H),3.10(t,J=7.1Hz ,2H),2.73(t,,J=7.5Hz ,2H). LC-MS [M+H] + =208.0

[0208] Step 4: N-(1-benzylpiperidin-4-yl)-3-(6-(4-methylpiperazin-1-yl)imidazole[1,2-b]pyridazin-3-yl)propanamide 50 (LIT TB014). 3-(6-Hydroxyimidazo[1,2-b]pyridazin-3-yl)propanoic acid (1 equiv., 200 mg, 0.96 mmol) and N(Me)Cl (1 equiv., 105.8 mg, 0.96 mmol) were suspended in POCl (1.1 mL), and the resulting mixture was heated overnight under a nitrogen atmosphere. After cooling at room temperature, DMF was evaporated, and the crude material was purified by flash chromatography using EtOAc / MeOH / AcOH (8:2:0.5) as eluent to give 3-{6-chloroimidazo[1,2-b]pyridazin-3-yl}propanoic acid (100 mg, 46%). LC-MS (ES+APCI): 282.2 [M+Na + ],208.0[M+H] +

[0209] The above product (1 equiv., 50 mg, 0.22 mmol), BOP (1.2 equiv., 117.6 mg, 0.22 mmol), and NMM (1.5 equiv., 33.6 mg, 0.33 mmol) were suspended in DCM (1.5 mL). The reaction mixture was stirred at room temperature for 15 minutes, and then 4-amino-1-benzylpiperidine (42.17 mg, 45.3 μL, 0.22 mmol) was added, and the reaction was stirred at room temperature overnight (20 hours). Water (15 mL) was then added to the resulting mixture, and the aqueous solution was extracted twice with DCM (3 × 8 mL). The organic phases were combined, dried over NaSO, filtered, and concentrated under reduced pressure. The resulting oil was purified by silica gel flash chromatography using 8 / 2 EtOAc / MeOH as the eluent to give N-(1-benzylpiperidin-4-yl)-3-{6-chloroimidazo[1,2-b]pyridin-3-yl}propanamide 49 (65 mg, 74%). LC-MS [M+H] + =398.2

[0210] Using the same procedure as described for 9a (LIT-TB001), the above product 49 (1 Starting with 1-methylpiperazine (20.14 mg, 22.3 μL, 0.20 mmol, 2 equiv.), the title compound was obtained in 65% yield. LC-MS (ES+APCI): 484.2 [M+Na + ],462.2[M+H + ].

[0211] Preparation of triazolopyridazines The invention also provides a process for preparing appropriate N-substituted-triazolo[4,3-b]pyridazin-3-yl)propylpiperidin-4-amines of formula 56 (Scheme 10). Starting from N-benzyl-piperidin-4-one 51, amination with methyl 4-aminobutyrate in the presence of NaBHCN gave ethyl N-benzylpiperidine-4-aminobutanoate 52. To avoid intramolecular cyclization, 53 was first N-Boc protected (cpd 53) and then, after saponification, subjected to a peptide-type coupling reaction with hydrazinopyridazine 5 under conditions well known in the art. Cyclization under strongly acidic conditions (135 °C), followed by an SNAr-type amination reaction in the presence of 8a-g, afforded the target product 56.

[0212] [ka]

[0213] Conditions: a) H2N-(CH2)3CO2Et, AcOH, NaBH(AcO)3, DCM, 25°C, 12 hours; b) BOC2O, DCM, Et3N, 24 hours; c) NaOH, MeOH then 1N HCl (pH=6); d) BOP, NMM, DCM, 12 hours. e) AcOH, 150°C, 2 hours; f) EtOH, 150°C, μwave, 1 hour.

[0214] Example 11 Preparation of 1-benzyl-N-(3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propyl)piperidin-4-amine 56a (LIT-TB015) Step 1: 4-((1-benzylpiperidin-4-yl)amino)butanoate 52 To an ice-cold solution of 1-benzyl-piperidin-4-one 51 (1 equiv., 1.00 g, 5.28 mmol) in CHCl (35 ml) was added methyl 4-aminobutyrate hydrochloride (1 equiv., 0 To the reaction mixture were added 1.88 g, 5.28 mmol), acetic acid (3.5 equiv., 1.1 mL, 18.49 mmol), EtN (1.5 equiv., 802 mg, 1.1 mL, 3 mmol), and sodium triacetoxyborohydride (3 equiv., 3.5 g, 3 mmol). The mixture was allowed to reach room temperature and stirred for 16 h. The solution was then washed with saturated potassium bicarbonate solution, dried (NaSO), and concentrated. The crude product was purified by flash chromatography using EtOAc-MeOH (8:2) to give ethyl 4-((1-benzylpiperidin-4-yl)amino)butanoate 52 (m = 1.15 g, yield = 71%). 1 H NMR (400MHz, CDCl3) δ7.25-7.21(m,4H),7.20-7.14(m,1H),4.05(q,2H,J=7.0Hz). 343(s,2H),2.82-2.75(m,2H),2.62-2.61(bs,1H),2.59(t,2H,J=7.2Hz) ,2.43-2.36(m,1H),2.28(t,2H,J=7.2Hz),1.93-1.63(m,4H),1.33(dq,2H ,J=11.8Hz,J=3.6Hz). 13 C NMR (101MHz, CDCl3) δ174.6,138.3,129.2,128.3,127.0,62.9,52.7,48.7,42.7,31.4,29.0,18.1.

[0215] Step 2: Ethyl 4-((1-benzylpiperidin-4-yl)(tert-butoxycarbonyl)amino)butanoate 53 To a stirred solution of ethyl 4-((1-benzylpiperidin-4-yl)amino)butanoate (1 equiv., 1.2 g, 3.94 mmol) in DCM (15 mL) was added EtN (2 equiv., 797.7 mg, 7.88 mmol), followed by BocO (1.5 equiv., 1.29 g, 1.26 mmol), and the resulting mixture was stirred overnight. The solution was then washed with water, dried (NaSO), and concentrated. The crude was purified by flash chromatography to give the title compound 53 (m = 1.35 g, yield = 85%). 1H NMR(400MHz,CDCl3)δ7.28-7.11(m,5H),4.06(q,2H,J=7.2Hz),3.96-3.79(m,1H),3.41(s,2H),3.11-2.99(m,2H),2.98(d,2H, J=12.0Hz), 2.20(t,2H,J=7.7Hz),2.02-1.91(m,2H),1.79-1.70(m,2H),1.68-1.63(m,4H),1.39(s,8H),1.19(t,3H,J=7.2Hz). 13 C NMR (101MHz, CDCl3) δ173.2,155.6,129.1,128.2,127.0,79.5,63.0,60.3,53.3,42.2,31.9,30.1,25.8,14.3.

[0216] Step 3: tert-Butyl (1-benzylpiperidin-4-yl)(4-(2-(6-chloropyridazin-3-yl)hydrazinyl)-4-oxobutyl)carbamate 54 Ethyl 4-((1-benzylpiperidin-4-yl)(tert-butoxycarbonyl)amino)butanoate 53 (1 equiv., 1.3 g, 3.21 mmol) was diluted with MeOH (5 mL). 1 N NaOH (15 mL) was added and the reaction mixture was stirred at room temperature overnight. The crude was acidified to pH = 6 with 2 N HCl and evaporated. The crude product (1 equiv., 1.0 g, 2.66 mmol), BOP (1.2 equiv., 1.4 g, 2.66 mmol), and NMM (2.5 equiv., 0.67 g, 730 μl, 6.64 mmol) were suspended in DCM (15 mL) and the reaction mixture was stirred at room temperature for 15 min. Then 3-chloro-6-hydrazinopyridazine 5 (1 equiv., 384 mg, 2.66 mmol) was added and the reaction was stirred at room temperature overnight (20 h). After evaporation of the volatiles, the crude was directly purified by silica gel flash chromatography using EtOAc / MeOH / Et3N 8 / 2 / 0.3 as the eluent to give the title compound (m=1.0 g, yield=75%). 1H NMR(400MHz,CDCl3)δ8.50(bs,1H),7.52(bs,1H),7.42-729(m,5H),7.27(d,1 H,J=9.5Hz),7.04(d,1H,J=9.9Hz),4.30-4.13(m,2H),4.04-3.89(m,1H),3.7(t,2H,J=4.9Hz),3.45(bs,2H) ,3.15-3.04(m,2H),2.83(t,2H,J=12.1Hz),2.27(t,2H,J=7.2Hz),1.85-1.77(m,4H),1.36(s,9H). LC-MS(ES+APCI):501(MH + ),401(-Boc)

[0217] Step 4: 1-benzyl-N-(3-(6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propyl)piperidin-4-amine 56a (LIT-TB015) A microwave vial was charged with ethyl 4-((1-benzylpiperidin-4-yl)(tert-butoxycarbonyl)amino)butanoate 54 (1 equiv., 400 mg, 0.82 mmol) and acetic acid (1.87 mL). The vial was capped appropriately and the mixing vessel was heated at 110° C. for 2 h. The mixture was cooled to room temperature and evaporated. The crude was coevaporated with cyclohexane and triturated with cold ether. The white solid was collected by filtration (210 mg, LC / MS 385.2 [M+H]) to give compound 55, which was used in the next step without further purification.

[0218] Using the same procedure A as described for 9a (LIT-TB001), starting from compound 55 (1 equiv., 100 mg, 0.25 mmol) and 1-methylpiperazine 8a (2 equiv., 100.1 mg, 57.6 μl), the title compound 56a was obtained under microwave irradiation (m = 40 mg, yield = 34%). LC-MS [M+H] + =449.2; 471.2 (M+Na)

[0219] Preparation of 57 (LIT-TB-058) The invention also provides a process for the reductive dehalogenation of 6-chlorotriazolopyridazine derivatives, specifically 7a-f, which were used as substrates for halogen / metal exchange in the presence of Pd(PPh) and HCOOH as the reducing agent (see Scheme 11).

[0220] [ka]

[0221] Conditions: a) Pd(PPh3)4 (4 mol%), HCOOH (1 equiv.), TEA (12 equiv.), DMF, 100°C, 45 min, μw.

[0222] Example 12 Preparation of 3-([1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(1-benzylpiperidin-4-yl)propanamide 57a (LIT-TB058) N-(1-benzylpiperidin-4-yl)-3-{6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl}propanamide 7a (1 equiv., 100 mg, 0.25 mmol) in dry DMF (2 mL) was treated with TEA (12 equiv., 314.6 mg, 0.43 mL, 3.1 mmol) and Pd(PPh3)4 (4 mol%, 11.6 mg). The vial was appropriately capped, degassed, and the contents were stirred at room temperature for 10 minutes. A solution of formic acid (1 equiv., 11.54 mg, 9.5 μl, 1 mmol) in dry DMF (0.4 mL) was then added, and the reaction mixture was heated by microwave irradiation at 100° C. for 45 minutes. After cooling, the reaction mixture was concentrated and, after chloride precipitation, purified by silica gel flash chromatography using DCM / MeOH, 90 / 10+2% NH to give the title compound as a yellow solid (m=26 mg, yield=26%). 1H NMR (400 MHz, methanol-d4) δ 8.58 (dd, J = 4.2 Hz, J = 1.6 Hz, 1H), 8.2 (dd, J = 9.5 Hz, J = 1.6 Hz, 1H), 7.36 (dd, J = 9.5 Hz, J = 4.3 Hz), 7.35-7.31 (m, 4H), 7.31-7.25 (m, 1H), 3.71-3.60 (m, 1H) ),3.52(s,2H),3.49(t,J=7.5Hz,2H),2.92-2.80(m,2H),2.84(t,J=7.5Hz,2H),2.13(d t,J=11.6Hz,J=2.0Hz,2H),1.82(dd,J=13.1Hz,J=3.5Hz),1.5(dq,J=11.9Hz,J=3.5Hz,2 H). ). 13 C NMR (101 MHz, methanol-d₄) δ 171.7, 149.5, 146.0, 144.4, 137.1, 129.4, 127.9, 127.0, 123.9, 121.1, 62.6, 51.9, 46.5, 31.6, 30.9, 19.7. LC-MS [M+H] + =365.20

[0223] Preparation of analogues 60a-f The invention also provides a process for the direct introduction of the 4-methyltetrahydropyridine moiety at the 6-position by means of N-methyl-piperid-3-en-4-ylboronate 58 under Suzuki-Miyaura conditions, followed by hydrogenation over Pd / C (Scheme 12).

[0224] [ka]

[0225] Conditions: a) PdCl2dppf.CH2Cl2, K2CO3, DMF / H2O; b) H2, Pd / C, MeOH.

[0226] Example 13 Preparation of N-(1-benzylpiperidin-4-yl)-3-(6-(1-methylpiperidin-4-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 60a (LIT-TB059) N-(1-benzyl-4-piperidyl)-3-(6-chloro-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)propanamide 7a (200 mg, 0.50 mmol, 1.0 equiv.) was solubilized in dimethylformamide (10 mL). Boronic acid pinacol ester 58 (110 mg, 0.50 mmol, 1.0 equiv.), potassium carbonate (210 mg, 1.50 mmol, 3.0 equiv.), and two drops of water were added. The reaction mixture was degassed for 20 min by bubbling with argon. Palladium complex PdCl2dppf.CHCl2 (41 mg, 0.05 mmol, 0.1 equiv.) was added portionwise, and the reaction vessel was sealed and heated at 80 °C for 18 h. After cooling, the solvent was removed under vacuum and the residue was purified by flash chromatography [Biotage®; column Biotage® 24 g; eluent: EtOAc / MeOH; gradient: 100 / 0 → 100 / 0 ( Purification by 100 / 0 → 70 / 30 (2 CV), 100 / 0 → 70 / 30 (12 CV), then 70 / 30 → 70 / 30 (3 CV)] gave compound 59 as a dark red powder (120 mg, 52% yield). LCMS confirmation: m / z = 460.2 (M+H).

[0227] N-(1-benzyl-4-piperidyl)-3-[6-(1-methyl-3,6-dihydro-2H-pyridin-4-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propenamide 59 (120 mg, 0.26 mmol, 1.0 equiv.) was solubilized in methanol (30 mL). After adding 10% palladium on activated carbon (145 mg, 0.14 mmol, 0.5 equiv.), the reaction mixture was hydrogenated under dihydrogen pressure (4 bar) at 20° C. for 6 hours. The reaction mixture was filtered through a Celite® pad, and the solvent was evaporated under vacuum. The residue was purified by flash chromatography (Biotage®; column AIT® 4 g; eluent: DCM / MeOH; gradient: 90 / 100 → 80 / 20 (10 CV)) to give compound 8 as a beige powder (53 mg, 44% yield). Further lyophilization was carried out to remove traces of solvent. 1H NMR(300MHz,CDCl3)δ7.98(d,J=9.6Hz,1H),7.33-7.22(m,5H),7.02(d,J=9.6Hz,1H),6.08(d,J=7.7Hz,1H),3.82-3.72(m,1H),3.49-3.43(m,4H),3 .04-2.99(m,2H),2.89(t,J=7.1Hz,2H),2.79-2.74(m,3H),2.35(s,3H),2 .17-2.06(m,4H),1.98-1.93(m,4H),1.93-1.83(m,2H),1.53-1.39(m,2H). 13 C NMR(75MHz,CDCl3)δ170.7,160.2,149.3,143.8,138.3,129.1(2C),128.2(2C),127.0,12 4.7,119.9,63.0,55.3(2C),52.2(2C),46.6,46.3,41.7,32.5,32.0(2C),30.8(2C),20.3 LCMS: m / z=462.2 (M+H).

[0228] Preparation of pyrazolopyridines Alternatively, the triazolopyridazine ring may be replaced by a pyrazolopyridine ring of general structure 66 in a four-step sequence shown in Scheme 13 below.

[0229] [ka]

[0230] Conditions: a) 3,4-dihydro-2H-pyran, pTsOH, THF; b) PdCl2dppf, CH2Cl2, K2CO3, toluene / EtOH; c) NMe-piperazine, MeCN, 160 °C, 4H μ-wave; d) Pd / C (10%), H2, EtOH; e) 6N HCl, MeCN; f) EDCI, HOBT, H2O, Et3N, DCM.

[0231] Example 14 Preparation of N-(1-benzylpiperidin-4-yl)-3-(5-(4-methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl)propanamide 66a (LIT-TB060) Step 1: 5-chloro-3-iodo-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazolo[4,3-b]pyridine 62 5-Chloro-3-iodo-1H-pyrazolo[4,3-b]pyridine 1 (1.0 g, 3.60 mmol, 1.0 equiv), 3,4-dihydro-2H-pyran (650 mg, 7.70 mmol, 0.7 mL, 2.1 equiv), and para-toluenesulfonic acid (150 mg, 0.80 mmol, 0.2 equiv) were solubilized in THF (10 mL) and stirred at 60 °C for 18 h. After cooling to room temperature, saturated NaHCO solution (50 mL) was added, and the mixture was extracted with ethyl acetate (3 × 75 mL). The organic layer was dried over magnesium sulfate and evaporated in vacuo. The residue was purified by flash chromatography (Biotage®; column AIT® 80 g; eluent: cyclohexane / DCM; gradient: 100 / 0 → 100 / 0 (3 CV), 100 / 0 → 0 / 100 (20 CV)] to give compound 3 as a colorless gum (1.30 g, 99% yield).

[0232] Step 2: (E)-3-(5-chloro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl)ethyl acrylate 64 5-Chloro-3-iodo-1-tetrahydropyran-2-yl-pyrazolo[4,3-b]pyridine 62 (1.0 g, 2.75 mmol, 1.0 equiv.) was solubilized in a mixture of toluene (10 mL) and ethanol (5 mL). After the addition of boronic acid pinacol ester 63 (810 mg, 3.58 mmol, 1.3 equiv.) and aqueous potassium carbonate (2 M) solution (5.60 mmol, 2.8 mL, 2.0 equiv.), the reaction mixture was degassed for 20 min by bubbling with argon. The palladium complex (115 mg, 0.14 mmol, 0.05 equiv.) was added portionwise, the reaction vessel was sealed and heated at 110° C. for 18 h. After cooling to room temperature, water (20 mL) was added and the mixture was extracted with ethyl acetate (3×50 mL). The organic layer was dried over magnesium sulfate and evaporated in vacuo. The residue was purified by flash chromatography (Biotage®; column AIT® 80 g; eluent: cyclohexane / EtOAc; gradient: 90 / 10→60 / 40 (20 CV)] to give compound 64 as a white solid (m=475 mg, yield=51%). LCMS confirmation: m / z=336.3 (M+H).

[0233] Step 3: 3-(5-(4-methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl)propanoic acid 65 Ethyl (E)-3-(5-chloro-1-tetrahydropyran-2-yl-pyrazolo[4,3-b]pyridin-3-yl)prop-2-enoate 64 (470 mg, 1.40 mmol, 1.0 equiv.) was solubilized in a mixture of N-methylpiperazine 6 (5 mL) and MeCN (5 mL). The reaction mixture was heated at 160° C. for 4 hours under microwave irradiation. The solvent was evaporated under vacuum, and the residue was purified by flash chromatography (Biotage®; Biotage® 24 g column; eluent: DCM / MeOH; gradient: 90 / 10 → 80 / 20 (20 CV)] to give compound 7 as a brown oil (340 mg, 60% yield). LCMS confirmation: m / z=400.50 (M+H).

[0234] Ethyl (E)-3-[5-(4-methylpiperazin-1-yl)-1-tetrahydropyran-2-yl-pyrazolo[4,3-b]pyridin-3-yl]prop-2-enoate (330 mg, 0.83 mmol, 1.0 equiv.) was solubilized in ethanol (30 mL). After adding 10% palladium on activated carbon (100 mg, 0.09 mmol, 0.1 equiv.), the reaction mixture was hydrogenated under hydrogen pressure (4 bar) at 50° C. for 24 hours. The reaction mixture was filtered through a Celite® pad, and the solvent was evaporated under vacuum to give 3-[5-(4-methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl]propanoic acid as a brown oil (m=335 mg, yield=99%). LCMS confirmation: m / z=402.1 (M+H).

[0235] 3-[5-(4-Methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl]propanoic acid (330 mg, 0.83 mmol, 1.0 equiv.) was solubilized in acetonitrile (5 mL). After adding aqueous HCl (6N) (5.0 mL), the reaction mixture was heated at 100° C. for 30 minutes under microwave irradiation. The solvent was evaporated under vacuum, and the aqueous residue was washed with dichloromethane (3×20 mL). The aqueous layer was evaporated and dried under vacuum to give compound 65 in a complex mixture with the salt. The residue was used in the following step without further purification. MS confirmation: m / z=290.25 (M+H).

[0236] Step 4: N-(1-benzylpiperidin-4-yl)-3-(5-(4-methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl)propanamide 66a Crude 3-[5-(4-methylpiperazin-1-yl)-1H-pyrazolo[4,3-b]pyridin-3-yl]propanoic acid 65 (crude, theoretical 0.83 mmol, 1.0 equiv.) and 1-benzylpiperidin-4-amine 10 (280 mg, 1.47 mmol, 0.30 mL, 1.8 equiv.) were solubilized in dimethylformamide (10 mL). EDCI.HCl (315 mg, 1.66 mmol, 2.0 equiv.), HOBt (225 mg, 1.66 mmol, 2.0 equiv.), and EtN (725 mg, 7.17 mmol, 1.0 mL, 8.6 equiv.) were added to the reaction mixture, which was stirred at room temperature for 24 h. The reaction mixture was filtered, and the filtrate was evaporated to dryness under high vacuum. Water (10 mL) was added to the residue. The remaining aqueous solution was washed successively with ethyl acetate (3x20 mL) and dichloromethane (3x20 mL). The aqueous layer was evaporated and dried under vacuum. The residue was solubilized in isopropanol. The resulting mixture was precipitated with diisopropyl ether. After trituration and filtration, the filtrate was evaporated under vacuum. Another trituration in dichloromethane, followed by filtration, led to the detection of the target compound 11 in the filtrate. The residue containing 11 was purified by flash chromatography (Biotage®; column Biotage® 24 g; eluent: EtOAc / MeOH; gradient: 100 / 0 → 100 / 0 (3 CV), 100 / 0 → 70 / 30 (15 CV), then 70 / 30 → 70 / 30 (15 CV), followed by DCM / NH3 (7N) in MeOH; gradient: 100 / 0 → 100 / 0 (3 CV), 100 / 0 → 70 / 30 (15 CV), then 70 / 30 → 70 / 30 (5 CV)), to give compound 11 in a mixture with the EDCI derivative. A second purification by semi-preparative HPLC (Gilson PLC 2020, column C8 Princeton SPHER. 60-10 μm, gradient: water / acetonitrile (0.1% HCOOH) 95 / 5 → 95 / 5, 10 min and 95 / 5 → 0 / 100, 25 min) followed by direct lyophilization gave pure compound 66 as a beige powder (formate 0.3 equiv.) (22 mg, 7% yield). The hydrochloride salt form of 66 was prepared by solubilizing it in dioxane (5.0 mL) and adding a 4N HCl solution in dioxane (5.0 mL). After stirring at room temperature for 1 h, the solvent was evaporated, and the residue was lyophilized to give 66a as the hydrochloride salt as a beige powder (m = 22 mg, 5% yield). 1 H NMR (300MHz, DMSO-d6): δ7.78(d,J=7.6Hz,1H),7.71(d,J=9.2Hz,1H),7.33-7.22(m,5H),7.02(d,J=9.2Hz,1H),3.65-3.30(m,7H) ),3.05-2.98(m,2H),2.80-2.72(m,2H),2.65-2.50(m,5H),2.31(s,3H),2.11-2.25(m,2H),1.70-1.65(m,2H),1.43-1.35(m,2H). 13C NMR (75MHz, DMSO-d6): δ170.8,163.3,155.4,137.5,136.4,129.3,129.0,128. 2,127.1,120.6,109.4,61.7,54.0,51.7,45.5,45.3,45.0,34.1,31.1,21.7). LCMS: m / z=462.2 (M+H).

[0237] Synthesis of fluorescent analogue (LIT-TB043) Fluorescent analogs of compound 9a (LIT-TB001) can be prepared by coupling a fluorogenic probe (e.g., DY-647P1-NHS-ester) to an appropriately substituted primary amine, as shown in Scheme 14.

[0238] [ka]

[0239] Conditions: a) 67, K2CO3, DMF, 80 °C, 16 h; b) PPh3, MeOH / H2O, room temperature overnight; c) DY-647P1-NHS-Ester, DIEA, DMSO, room temperature, overnight.

[0240] Preparation of (2E)-1-[6-[2-[2-[2-[4-[3-[3-[(1-benzyl-4-piperidyl)amino]-3-oxo-propyl]-[1,2,4]triazolo[4,3-b]pyridazin-6-yl]piperazin-1-yl]ethoxy]ethoxy]ethylamino]-6-oxo-hexyl]-2-[(2E,4E)-5-[1-(2-methoxyethyl)-3,3-dimethyl-5-sulfonato-indol-1-ium-2-yl]penta-2,4-dienylidene]-3,3-dimethyl-indoline-5-sulfonate; dihydrochloride (LIT-TB043) Step 1: 3-(6-(4-(2-(2-(2-aminoethoxy)ethoxy)ethyl)piperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)-N-(1-benzylpiperidin-4-yl)propanamide hydrochloride 68 N-(1-benzylpiperidin-4-yl)-3-[6-(piperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide 9d (1 equiv., 10.4 mg, 0.0232 mmol), ethyl 2-[2-(2-azidoethoxy)ethoxy]methanesulfonate 67 (1.5 equiv., 8.81 mg, 0.0348 mmol), and KCO (2 equiv., 6.41 mg, 0.0464 mmol) were solubilized in dry DMF (0.2 mL). The reaction was flushed with argon three times, and the mixture was stirred at 80 °C for 16 h. The crude product was filtered over a pad of Celite and washed with MeOH. The filtrate was evaporated to give a yellowish solid (compound 69), which was solubilized in a mixture of MeOH / HO (3 / 1, 1 ml). PPh3 (2.5 equiv., 15.2 mg, 0.058 mmol) was added, and the reaction was stirred at room temperature overnight. DMSO was added to the crude, and then the mixture was evaporated. The remaining DMSO phase was purified by reverse-phase chromatography (HO + 0.05% HCl / MeOH) to give the compound as a white solid (m = 7.0 mg, yield = 44%).

[0241] Step 2: (2E)-1-[6-[2-[2-[2-[4-[3-[3-[(1-benzyl-4-piperidyl)amino]-3-oxo-propyl]-[1,2,4]triazolo[4,3-b]pyridazin-6-yl]piperazin-1-yl]ethoxy]ethoxy] [ethylamino]-6-oxo-hexyl]-2-[(2E,4E)-5-[1-(2-methoxyethyl)-3,3-dimethyl-5-sulfonato-indol-1-ium-2-yl]penta-2,4-dienylidene]-3,3-dimethyl-indoline-5-sulfonate; dihydrochloride 69 (LIT-TB043) 3-[6-(4-{2-[2-(2-aminoethoxy)ethoxy]ethyl}piperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]-N-(1-benzylpiperidin-4-yl)propanamide hydrochloride 68 (1 equiv., 0.855 mg, 0.00124 mmol) and DY-647P1-NHS-ester (1 equiv., 1 mg, 0.00124 mmol) were solubilized in dry DMSO (0.3 ml). DIEA (5 equiv., 0.802 mg, 1.03 μL, 0.0062 mmol) was added, and the reaction was flushed with Ar three times. The reaction was stirred at room temperature overnight. The crude was directly purified by reverse phase chromatography (H2O+0.05% HCl / MeOH) to give LIT-TB043 as a blue solid (m=1.58 mg, yield=98%). LC-MS[2Na(m / 2)]=646

[0242] II. Results material Recombinant human BDNF and NGF were obtained from Peprotech. Recombinant human TrkBECD-Fc was obtained from R&D Systems, and BDNF-biotin was purchased from Alomone Labs. AAV-GCAMP6F virus was generated at the U Penn Vector Core. Phosphatase inhibitor cocktail 2 was purchased from Roche, and protease inhibitor Complete ultra-cocktail was purchased from Sigma. Antibodies were obtained from different sources: polyclonal anti-TrkB, anti-phosphotyrosine (4G10), and anti-pY816-TrkB from Millipore; monoclonal anti-TrkB from BD Biosciences; anti-phospho-S473 Akt, anti-AKT, anti-phospho-ERK1 / 2, anti-ERK1 / 2, anti-pY516-TrkB, and anti-pY706 / 707-TrkB from Cell Signaling; HRP-conjugated streptavidin from Amersham Biosciences; and anti-beta III-tubulin from Millipore.

[0243] Intraperitoneal administration to mice Adult C57BL / 6 male mice were intraperitoneally injected with saline (0.9% NaCl) or LIT-TB001 (dissolved in saline solution) at different doses ranging from 0.1 to 5.0 mg / kg. A volume of 10 μl / g body weight was injected. One hour later (unless otherwise stated), the mice were decapitated, blood was collected, and the brains were rapidly removed on ice. The cortex and hippocampus were then dissected, and the tissues were rapidly washed with ice-cold PBS, transferred to ice-cold solubilization buffer, and then homogenized at 4°C. Samples were centrifuged at 10,000 x g for 10 min at 4°C. Protein concentrations were determined, and equivalent amounts of protein were loaded. Western blots were performed as described above.

[0244] TrkB selectivity The development of Trk canonical (orthosteric) agonists is limited by a lack of receptor selectivity, as there are three common and similar types of Trk receptors: TrkA, TrkB, and TrkC. Each of these receptors has a different binding affinity for a particular type of neurotrophin. The differences in signal transduction initiated by these different types of receptors are important for generating diverse biological responses.

[0245] TrkB PAMs may have some advantages in terms of selectivity. The selectivity of LIT-TB001 as a TrkB PAM was evaluated against TrkB in vitro (Figure 1).

[0246] The selectivity of LIT-TB001 for signaling activation and biological function was tested in PC12-TrkB or PC12-TrkA cells in the presence of BDNF (TrkB) or NGF (TrkA). Key experiments to test TB selectivity: Trk phosphorylation, ERK phosphorylation, and neurite outgrowth were repeated in either TrkA- or TrkB-expressing cells (Figure 1).

[0247] In PC12-TrkA cells, LIT-TB001 did not induce ERK or TrkA phosphorylation in the presence or absence of NGF. In PC12-TrkB cells, ERK and TrkB phosphorylation was induced only in the presence of BDNF. The same observation was made at the functional level of neurite outgrowth.

[0248] In conclusion, LIT-TB001 enhances BDNF-dependent signaling pathways (pERK and pTrkB) and biological functions (neurite outgrowth), but not NGF-dependent. These results demonstrate the selectivity of TB compounds for the Trk family.

[0249] Next, we performed kinome profiling to test the selectivity of LIT-TB001 over other kinases. The kinome profile of 45 kinases showed good TrKB selectivity, as LIT-TB001 neither activated nor blocked the catalysis of the kinases tested at a concentration of 10 μM (among the kinases, TrkA was most similar to TrkB, confirming our previous results) (Figure 2).

[0250] In vitro activity of LIT-TB derivatives in the TrkB phosphorylation assay The in vitro activities of LIT-TB derivatives in the TrkB phosphorylation assay are listed in Table 1 below.

[0251] [Table 1]

[0252] In vivo target engagement In vivo TrkB engagement by LIT-TB001 was evaluated in mouse brains after peripheral injection. C57Bl6 male mice received intraperitoneal injections of 0.5 and 1 mg / kg ip. One hour later, the brains were carefully removed and the cortex and hippocampus were subdissected. BDNF and TrkB are known to play important roles in these two regions. The level of TrkB phosphorylation at tyrosine 816 was analyzed by Western blot (Figure 3). These results clearly demonstrate that low doses of LIT-TB001 (0.5 and 1 mg / kg, i.p.) efficiently increase TrkB activation in the brain one hour after systemic administration in mice.

Claims

1. 1. A pharmaceutical composition comprising: (a) a LIT-TB compound of formula I, 【Chemistry 1】 During the ceremony, R １ -G- is selected from the group comprising groups of the following formulae: 【Chemistry 2】 Same or different X １ and X ２ independently represent CH or N; X ３ is C or N, X ４ is N, Y represents N or CH; r is an integer from 1 to 3; A is C(O)NH, NHC(O), or NH; m is equal to 0, 1, or 2; m' is equal to 0, 1, or 2, and m+m'≦3; t is an integer from 0 to 5, Each R may be the same or different ６ The group is selected from the group comprising H, fluoride, optionally branched C1-C6 alkyl chains and C1-C6 alkoxy groups; Same or different T １ and T ２ But independently CH ２ , CHR ６ or C═O, Z is selected from the group comprising a bond, H, and an optionally branched C1-C3 alkyl chain optionally containing a heteroatom selected from the group comprising O or N; R 2 is zero when Z is H, or R ２ But H, or Formula Ib: 【Transformation 3】 wherein each R 7a , R 7b , and R 7c is independently selected from the group consisting of H, F, Cl, Me, and OMe; or a cyclohexyl group, or the LIT-TB compound of formula I, which is a methylimidazole group; or a pharmaceutically acceptable salt thereof; (b) a pharmaceutically acceptable excipient or carrier.

2. The LIT-TB compound is X １ , X ２ , and X ３ 10. The composition of claim 1, wherein at least one of:

3. A compound of formula I, 【Chemistry 4】 During the ceremony, R １ -G- is selected from the group comprising groups of the following formulae: 【Transformation 5】 Same or different X １ and X ２ independently represent CH or N; X ３ is C or N, X ４ is N, Y represents N or CH; r is an integer from 1 to 3; A is C(O)NH, NHC(O), or NH; m is equal to 0, 1, or 2; m' is equal to 0, 1, or 2, and m+m'≦3; t is an integer from 0 to 5, Each R may be the same or different ６ The group is selected from the group comprising H, fluoride, optionally branched C1-C6 alkyl chains and C1-C6 alkoxy groups; Same or different T １ and T ２ But independently CH ２ , CHR ６ or C═O, Z is selected from the group comprising a bond, H, and an optionally branched C1-C3 alkyl chain optionally containing a heteroatom selected from the group comprising O or N; R 2 is zero when Z is H, or R ２ But H, or Formula Ib: 【Transformation 6】 wherein each R 7a , R 7b , and R 7c is independently selected from the group consisting of H, F, Cl, Me, and OMe; or a cyclohexyl group, or is a methylimidazole group, or a pharmaceutically acceptable salt thereof, N-(1-benzyl-4-piperidyl)-3-[6-(4-methylpiperazin-1-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide, and A compound of Formula I or a pharmaceutically acceptable salt thereof, excluding N-(1-benzyl-4-piperidyl)-3-[6-(1-piperidyl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]propanamide.

4. A pharmaceutical agent for use in treating a disease selected from the group consisting of neurodegenerative diseases, obesity, type 2 diabetes, mood disorders, spinal cord injury, stroke, and ischemia, comprising the compound of claim 3 or a pharmaceutically acceptable salt thereof.

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