Pyrazine compounds useful in the treatment of parasitic protozoan infections

Abstract

The present application relates to compounds of formula (I) and their pharma- ceutically acceptable salts or stereoisomers, pharmaceutical compositions thereof and their use in the treatment and prevention of systemic infectious diseases, for example parasitic protozoan infections such as malaria, in particular infections caused by Plasmodium falciparum: [Formula 1] JPEG2024543882000045.jpg53164

Description

[Technical field]

[0001] This application relates to compounds and pharma- ceutically acceptable salts thereof, compositions thereof, and their use in the treatment and prevention of systemic infectious diseases, for example parasitic protozoan infections such as malaria, particularly infections caused by Plasmodium falciparum. [Background technology]

[0002] Parasitic infections cause a variety of diseases of medical and veterinary importance, such as malaria in humans and coccidiosis in birds, fish and mammals. Many diseases are life-threatening to the host and cause significant economic losses in the livestock industry.

[0003] Malaria is caused by the parasitic protozoan Plasmodium genus, which infects and destroys red blood cells, causing fever, severe anemia, and cerebral malaria, and if left untreated, can lead to death. There are five types of malaria parasites: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium falciparum, and Plasmodium noursi. The most virulent is Plasmodium falciparum. In 2019, an estimated 229 million people were infected with malaria in 87 malaria-endemic countries, and an estimated 409,000 people died from malaria (World malaria report 2020: 20 years of global progress and challenges. Geneva: World Health Organisation; 2020, Switzerland).

[0004] Effective oral formulations for the prevention and treatment of malaria are known in the art. For example, known treatments / preventions include artemisinin and artemisinin-based combination therapy (ACT). ACT is in fact the standard treatment for Plasmodium falciparum in uncomplicated cases (WHO Guidelines for malaria. Geneva: World Health Organization; 2021. Licence: CC BY-NC-SA 3.0 IGO). However, artemisinin is associated with delayed clearance of the parasite and less favorable clinical outcomes. Of particular concern is the emergence of resistance to ACT.

[0005] One approach to address this problem is to develop new therapeutic agents with new mechanisms of action. International patent application PCT / EP2016 / 074875 (published as WO2017 / 067881) discloses pyrazine compounds and their use in the treatment of parasitic protozoan infections. However, there is a need to develop new therapeutic agents with improved physicochemical properties, whole cell potency, in vivo efficacy, and predicted in vitro toxicity. Summary of the Invention

[0006] In a first aspect, the present invention provides a compound of formula (I): [ka] or a pharma- ceutically acceptable salt or stereoisomer thereof, wherein R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of H, halo, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; or R 1 and R2 together with the atom to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 3 and R 4 are each independently selected from the group consisting of H, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; or R 1 and R 3 together with the atom to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 2 and R 4 are each independently selected from the group consisting of H, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 5 is selected from the group consisting of halo and C1-C6 alkyl.

[0007] In a second aspect, the present invention provides a compound selected from the group consisting of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, and N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

[0008] In another aspect of the present invention, there is provided a pharmaceutical composition comprising a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof, and a pharma- ceutically acceptable excipient.

[0009] In a fourth aspect of the present invention there is provided a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof for use in the treatment of a parasitic protozoan infection.

[0010] In a fifth aspect of the invention there is provided the use of a compound of formula (I), or a pharmaceutical composition comprising a compound of formula (I), in the manufacture of a medicament for the treatment of a parasitic protozoan infection.

[0011] In a sixth aspect, the present invention provides a method of treating a parasitic protozoan infection in a human, comprising administering to the human a therapeutically effective amount of a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof, or a pharmaceutical composition.

[0012] In a seventh aspect, the present invention provides a combination comprising (a) a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof, and (b) at least one other antimalarial agent.

[0013] In an eighth aspect, the present invention provides a method of treating a parasitic protozoan infection in a human comprising administering to the human a therapeutically effective amount of the combination.

[0014] The present invention will be further illustrated, but not limited to, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 shows the X-ray powder diffraction pattern of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide (Example 4). [Diagram 2]FIG. 1 shows the X-ray powder diffraction pattern of N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide (Example 10). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Description of the Invention As mentioned above, in a first aspect of the present invention, there is provided a compound of formula (I): [ka] or a pharma- ceutically acceptable salt or stereoisomer thereof, wherein R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of H, halo, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; or R 1 and R 2 together with the atom to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 3 and R 4 are each independently selected from the group consisting of H, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; or R 1 and R 3 together with the atom to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 2 and R 4are each independently selected from the group consisting of H, C1-C6 alkyl, and 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of O, S, SO, SO2, NH, and NC1-C6 alkyl; R 5 is selected from the group consisting of halo and C1-C6 alkyl.

[0017] In one embodiment, R 5 is halo. In one embodiment, R 5 is fluoro (F).

[0018] In one embodiment, R 5 is C1-C6 alkyl. In one embodiment, R 5 is methyl.

[0019] In one embodiment, R 3 is H. In one embodiment, R 3 is H and R 5 is halo, particularly fluoro. In one embodiment, R 3 is H and R 5 is C1-C6 alkyl, in particular methyl.

[0020] In one embodiment, R 3 and R 4 is H. In one embodiment, R 3 and R 4 is H and R 5 is halo, particularly fluoro. In one embodiment, R 3 and R 4 is H and R 5 is C1-C6 alkyl, in particular methyl.

[0021] In one embodiment, R 1 and R 2 together with the atoms to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring. 1 and R 2together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring, in particular a 4-membered cycloalkyl ring; R 5 is halo, especially fluoro. 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 5 is C1-C6 alkyl, particularly methyl. In one embodiment, R 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 3 is hydrogen. In one embodiment, R 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 3 and R 4 is hydrogen. In one embodiment, R 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring, in particular a 4-membered cycloalkyl ring; R 3 and R 4 is hydrogen, and R 5 is halo, particularly fluoro. In one embodiment, R 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 3 and R 4 is hydrogen. In one embodiment, R 1 and R 2 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 3 and R 4 is hydrogen, and R 5 is C1-C6 alkyl, in particular methyl.

[0022] In one embodiment, the compound of formula (I) is N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] It is.

[0023] In one embodiment, the compound of formula (I) is in the form of the free base of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

[0024] In one embodiment, the compound of formula (I) is in the form of the free base of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide: i) an X-ray powder diffraction pattern (XRPD) substantially as shown in FIG. 1; and / or ii) has an X-ray powder diffraction pattern (XRPD) with specific peaks at 6.7, 11.2, 12.7, 13.4, 16.2, 16.6, 17.9, 20.9, 26.7, and 28.2 degrees 2θ values ​​(±0.1° 2θ experimental error).

[0025] In one embodiment, the compound of formula (I) is N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, which is a pharma- ceutically acceptable sulfate salt.

[0026] In one embodiment, the compound of formula (I) is in the form of a pharma- ceutically acceptable dihydrochloride salt.

[0027] In one embodiment, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof is N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] It is.

[0028] In one embodiment, R 1 and R 2 are each C1-C6 alkyl. In one embodiment, R 1 and R 2 are each C1-C6 alkyl, R 5 is halo, particularly fluoro. In one embodiment, R 1 and R 2 and R 5 are each C1-C6 alkyl. In one embodiment, R 1 and R 2 are each C1-C6 alkyl, R 3 is H. In one embodiment, R 1 and R 2 are each C1-C6 alkyl, R 3 and R 4 Each is H. In one embodiment, R 1 and R 2 are each C1-C6 alkyl, R 5 is halo, especially fluoro, and R 3 is H. In one embodiment, R 1 and R 2 are each C1-C6 alkyl, particularly methyl, and R 5 is halo, especially fluoro, and R 3 and R 4 Each is H. In one embodiment, R 1 and R 2 and R 5 are each C1-C6 alkyl, R 3 is H. In one embodiment, R 1 and R 2 and R 5 are each C1-C6 alkyl, R 3 and R 4 are H, respectively.

[0029] In one embodiment, the compound of formula (I) is N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] It is.

[0030] In one embodiment, R 1 and R 3 together with the atoms to which they are both attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring. 1 and R 3 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring, in particular a 6-membered cycloalkyl ring; R 5 is halo, particularly fluoro. In one embodiment, R 1 and R 3 together with the atom to which they are attached form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring; R 5 is C1-C6 alkyl, in particular methyl.

[0031] In one embodiment, the compound of formula (I) is N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] It is.

[0032] In one embodiment, the compound of formula (I) is N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide in the form of the free base.

[0033] In one embodiment, the compound of formula (I) is N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide in the form of the free base: i) an X-ray powder diffraction pattern (XRPD) substantially as shown in FIG. 2; and / or ii) has an X-ray powder diffraction pattern (XRPD) with specific peaks at 5.4, 10.8, 15.3, 16.6, 18.2, 20.1, 21.8, 22.4, 28.1, and 31.7 degrees 2θ values ​​(±0.1° 2θ experimental error).

[0034] In each embodiment in which the compound of formula (I) is N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, the compound may be N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

[0035] In one embodiment, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof is selected from the group consisting of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, and N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

[0036] In one embodiment, the invention provides a pharma- ceutically acceptable salt of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, or N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

[0037] definition As used herein, the term "alkyl" refers to a saturated, straight or branched chain hydrocarbon group. The term "C1-C6 alkyl" refers to an alkyl group containing from 1 to 6 carbon atoms. Exemplary alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, sec-pentyl, 3-pentyl, and sec-isopentyl.

[0038] The term "halogen" refers to a chloro, iodo, bromo, or fluoro group.

[0039] The term "compound of the present invention" refers to any one of the compounds of the present invention as defined above. Specifically, the term as used herein includes, but is not limited to, a compound of formula (I) or its pharma-ceutically acceptable salt or stereoisomer, and refers to any one of the formulas described herein.

[0040] It will be further understood that compounds of the present invention, such as compounds of formula (I), may exist in different tautomeric forms. Tautomers refer to isomeric forms of a compound that are in equilibrium with each other. The concentration of isomers will vary depending on the environment in which the compound is present.

[0041] The term "pharmaceutical acceptable" refers to compounds (including salts), materials, compositions, and dosage forms that are suitable for use in contact with the tissues of human or animals without undue toxicity, irritation, or other side effects / complications.

[0042] In one aspect, the present invention provides a pharma- ceutically acceptable salt of the compound of formula (I).Pharmaceutically acceptable salts include, but are not limited to, those described in Berge, J.Pharm.Sci., 1977,66,1-19, or those listed in PH Stahl and CG Wermuth, Handbook of Pharmaceutical Salts:Properties,Selection and Use,Second Edition,John Wiley & Sons,March 2011.

[0043] Where the functionality of the compound allows, suitable pharma- ceutically acceptable salts of the compound of formula (I) can be formed, including acid addition salts or base addition salts. Acid addition salts can be formed by reaction with a suitable acid, optionally in a suitable solvent such as an organic solvent, resulting in a salt that can be isolated by crystallization and filtration. Base addition salts can be formed by reaction with a suitable base, optionally in a suitable solvent such as an organic solvent, resulting in a salt that can be isolated by crystallization and filtration.

[0044] Representative pharma- ceutically acceptable acid addition salts include 4-acetamidobenzoate, acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate (besylate), benzoate, bisulfate, bitartrate, butyrate, calcium edetate, camphorate, camphorsulfonate (camsylate), caprate (decanoate), caproate (hexanoate), caprylate (octanoate), cinnamate, citrate, cyclamate, digluconate, 2,5-dihydroxybenzoate, disuccinate, dodecyl sulfate, and the like. Salts (estolate), edetate (ethylenediaminetetraacetate), estolate (lauryl sulfate), ethane-1,2-disulfonate (edisylate), ethanesulfonate (esylate), formate, fumarate, galactarate (mucate), gentisate (2,5-dihydroxybenzoate), glucoheptonate (glucoceptate), gluconate, glucuronate, glutamate, glutarate, glycerophosphate, glycolate, hexylresorcinate, hippurate, hydrabamine (N,N'-di(dehydroabietic) (p-ethylenediamine), hydrobromide, hydrochloride, hydroiodide, hydroxynaphthoate, isobutyrate, lactate, lactobionate, laurate, malate, maleate, malonate, mandelate, methanesulfonate (mesylate), methylsulfate, mucate, naphthalene-1,5-disulfonate (napadisilate), naphthalene-2-sulfonate (napsilate), nicotinate, nitrate, oleate, palmitate, p-aminobenzenesulfonate, p-aminosalicylate, pamoate (embonate), These include, but are not limited to, pantothenate, pectinate, persulfate, phenylacetate, phenylethylbarbiturate, phosphate, polygalacturonate, propionate, p-toluenesulfonate (tosylate), pyroglutamate, pyruvate, salicylate, sebacate, stearate, acetate, succinate, sulfamate, sulfate, tannate, tartrate, theoclate (8-chlorotheophylline), thiocyanate, triethiodide, undecanoate, undecylenate, and valerate salts.

[0045] Representative pharma- ceutically acceptable base addition salts include aluminum, 2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIS, tromethamine), arginine, benethamine (N-benzylphenethylamine), benzathine (N,N'-dibenzylethylenediamine), bis-(2-hydroxyethyl)amine, bismuth, calcium, chloroprocaine, choline, clemizole (1-p-chlorobenzyl-2-pyrrolidone-1'-ylmethylbenzimidazole), cyclohexyl ether, ... These include, but are not limited to, diethylamine, diethyltriamine, dimethylamine, dimethylethanolamine, dopamine, ethanolamine, ethylenediamine, L-histidine, iron, isoquinoline, lepidine, lithium, lysine, magnesium, meglumine (N-methylglucamine), piperazine, piperidine, potassium, procaine, quinine, quinoline, sodium, strontium, f-butylamine, and zinc.

[0046] In one embodiment, the present invention provides the ditrifluoroacetate salt of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide. [ka] , N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide 2:1 hydrochloride [ka] , and N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide sulfate [ka] A pharma- ceutically acceptable salt of a compound of formula (I) selected from:

[0047] In one embodiment, the present invention provides the 2:1 hydrochloride salt of N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, [ka] 2:1 ditrifluoroacetate salt of N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka]

[0023] The present invention provides a pharma- ceutically acceptable salt of a compound of formula (I) wherein:

[0048] In one embodiment, the present invention provides the difluoroacetate salt of N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide. [ka]

[0023] The present invention provides a pharma- ceutically acceptable salt of a compound of formula (I) wherein:

[0049] In one embodiment, the present invention provides a pharma- ceutically acceptable salt of a compound of formula (I) selected from: N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide 2:1 hydrochloride [ka] and the 2:1 trifluoroacetate salt of N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] .

[0050] The present invention includes within its scope all possible stoichiometric and non-stoichiometric forms of the salts of the compounds of formula (I). As used herein, the term "therapeutically effective amount" means any amount that results in improved treatment, cure, prevention, or amelioration of a disease, disorder, or side effect, or a reduction in the rate of progression of a disease or disorder, compared to a corresponding human subject that has not received such amount.

[0051] The appropriate "therapeutically effective amount" will depend on a variety of factors, such as, for example, the age and weight of the human subject, the precise condition requiring treatment and its severity, the nature of the formulation, and the route of administration, and is ultimately at the discretion of the attending physician.

[0052] The compounds of formula (I) contain one or more asymmetric centers (also called chiral centers) and therefore can exist as individual enantiomers, diastereomers, or other stereoisomers, or as mixtures thereof. Chiral centers, such as chiral carbon atoms, can also be present in substituents, such as alkyl groups. If the stereochemistry of a chiral center present in formula (I) or in any chemical structure shown herein is not specified, the structure is intended to encompass any stereoisomers and all mixtures thereof. Thus, the compounds of formula (I) containing one or more chiral centers can be used as racemic mixtures and racemates, racemic modifications, including enantiomerically enriched mixtures, or as enantiomerically pure individual stereoisomers.

[0053] For solvates of the compounds of the present invention or their salts in crystalline form, those skilled in the art will understand that solvent molecules may be incorporated into the crystal lattice during crystallization to form pharma- ceutically acceptable solvates. Solvates may include non-aqueous solvents such as ethanol, isopropanol, DMSO, acetic acid, ethanolamine, ethyl acetate, and the like, and may also include water as the solvent incorporated into the crystal lattice. Solvates in which water is the solvent incorporated into the crystal lattice are typically referred to as "hydrates". Hydrates include not only stoichiometric hydrates, but also compositions containing variable amounts of water. The present invention includes all such solvates.

[0054] The present invention also includes various deuterated forms of each of the compounds of formula (I) or its pharmaceutically acceptable salts or stereoisomers.Each available hydrogen atom bonded to a carbon atom may be independently replaced with a deuterium atom.Those skilled in the art will know how to synthesize the deuterated forms of the compounds of formula (I) of the present invention or its pharmaceutically acceptable salts or stereoisomers.For example, deuterated substances such as alkyl groups can be prepared by conventional techniques.

[0055] Thus, in some embodiments, compounds are included that are identical to the compounds recited in formula (I) herein, but are isotopically labeled with respect to the fact that one or more atoms are replaced by an atom having an atomic mass or mass number different from the atomic mass or mass number normally found in nature. Examples of isotopes that can be incorporated into the compounds of the present invention include isotopes of hydrogen, carbon, nitrogen, oxygen, fluorine, iodine, and chlorine, e.g., 3 H, 11 C. 14 C. 18 F, 123 I, or 125 I can be mentioned.

[0056] Compounds of the invention, or pharma- ceutically acceptable salts or stereoisomers thereof, that contain the aforementioned isotopes and / or other isotopes of other atoms are within the scope of the invention. Isotopically labeled compounds of the invention, e.g.3 H or 14 Compounds incorporating radioactive isotopes, such as C, are useful in drug and / or substrate tissue distribution assays. Tritiated isotopes, i.e. 3 H, and carbon-14, i.e. 14 C is particularly preferred due to its ease of preparation and detectability. 11 C and 18 F isotopes are particularly useful in PET (positron emission tomography).

[0057] As the compounds of the invention are intended for use in pharmaceutical compositions, it will be readily understood that each is provided in substantially pure form, for example at least 60% pure, in some embodiments at least 75% pure, in some embodiments at least 85% pure, and in other embodiments at least 90% or 95% pure, particularly at least 98% pure (percentages by weight). Impure preparations of the compounds may be used to prepare purer forms for use in the pharmaceutical compositions.

[0058] The compound of formula (I) or its pharma- ceutically acceptable salt or stereoisomer can exist as a solid or liquid, both of which are included in the present invention. In the solid state, the compound of formula (I) or its pharma- ceutically acceptable salt or stereoisomer can exist as an amorphous material or a crystalline form, or as a mixture thereof. The compound of formula (I) or its pharma- ceutically acceptable salt or stereoisomer can exist in solvated form, which can be formed when a solvent molecule is incorporated into the crystal lattice during crystallization. The solvate can include non-aqueous solvents such as ethanol, isopropanol, dimethylsulfoxide (DMSO), acetic acid, ethanolamine, ethyl acetate, and can also include water as the solvent incorporated into the crystal lattice. The solvate, which is the solvent in which water is incorporated, is typically referred to as a "hydrate". Thus, in an embodiment, the present invention provides a solvate of the compound of formula (I), for example a hydrate.

[0059] As used herein, the term "optionally" means that the subsequently described event(s) may or may not occur, and includes both the event(s) that occur and the event(s) that do not occur. For example, when used in connection with the term "substituted," i.e., "optionally substituted" means that the subsequently described substituent may or may not be present.

[0060] As used herein, the term "treatment" refers to (1) amelioration or prevention of the condition being treated or one or more biological symptoms of the condition being treated; (2) (a) interfering with one or more points in the biological cascade that leads to or is responsible for the condition being treated; or (b) interfering with one or more biological symptoms of the condition being treated; or (3) alleviating one or more symptoms or effects associated with the condition being treated. Those skilled in the art will appreciate that "prevention" is not an absolute term. In medicine, "prevention" is understood to refer to the prophylactic administration of a drug to significantly reduce the likelihood or severity of a condition or its biological manifestations, or to delay the onset of such a condition or its biological manifestations.

[0061] As used herein, an "effective amount" or a "safe and effective amount" means, within the scope of sound medical judgment, a sufficient amount of the compound to effect significant improvement in the condition being treated, yet low enough to avoid serious side effects (at a reasonable benefit / risk ratio).

[0062] How to use In one aspect, the present invention relates to a compound of formula (I), or a pharma- ceutically acceptable salt or stereoisomer thereof, for use in therapy.

[0063] The compounds of formula (I) or pharma- ceutically acceptable salts or stereoisomers thereof may be useful in the treatment of certain parasitic infections, such as parasitic protozoan infections caused by the malaria parasites Plasmodium falciparum, Eimeria, Pneumocytis carinii, Trypanosoma cruzi, Trypanosoma brucei, or Leishmania donovani.

[0064] In particular, the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer may be useful for treating infections caused by Plasmodium falciparum.Accordingly, the present invention relates to a method for treating such infections.Alternatively, the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer may be useful for treating infections caused by Plasmodium other than Plasmodium falciparum that causes human malaria.For example, the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer may be useful for treating infections caused by Plasmodium Vivax, i.e. malaria caused by infections caused by Plasmodium Vivax.

[0065] In one embodiment, the present invention relates to a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof for use in the treatment of a parasitic protozoan infection. In a particular embodiment, said protozoan infection is malaria or an infection with Plasmodium falciparum. In one embodiment, the present invention relates to a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof for use in the treatment of malaria caused by infection with Plasmodium falciparum.

[0066] In another aspect of the invention there is provided a method of treating a parasitic protozoan infection, the method comprising administering to a human in need thereof a pharma- ceutical effective amount of a compound of formula (I) or a pharma- ceutical acceptable salt or stereoisomer thereof, in one embodiment, the parasitic protozoan infection is malaria or an infection caused by Plasmodium falciparum.

[0067] In another aspect of the present invention, there is provided the use of a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof in the manufacture of a medicament for the treatment of a parasitic protozoan infection. In one embodiment, the parasitic protozoan infection is malaria or an infection caused by Plasmodium falciparum. Thus, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof can be used to treat malaria. Thus, the present invention also relates to a method of treating malaria, comprising administering a pharma- ceutically effective amount of a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof to a human in need thereof. Furthermore, the present invention relates to the use of a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof in the manufacture of a medicament for the treatment of malaria.

[0068] Those skilled in the art will understand that references to treatment herein refer to the treatment of established conditions, such as malaria. However, the compounds of the present invention may also be useful for the prevention of such diseases, such as malaria prevention. Thus, in one embodiment, treatment or prevention of diseases, such as malaria, is provided. In another embodiment, treatment of diseases, such as malaria, is provided. In a further embodiment, prevention of diseases, such as malaria, is provided.

[0069] In one embodiment, the malaria is multi-drug resistant malaria. Thus, in one embodiment, the compounds of formula (I) or pharma- ceutically acceptable salts or stereoisomers thereof may be useful in the treatment of susceptible and / or multi-drug resistant malaria.

[0070] In one embodiment, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof is used to treat a parasitic protozoan infection that is resistant to artemisinin combination therapy. In one embodiment, the compound of formula (I) or a pharma-ceutically acceptable salt or stereoisomer thereof is used to treat malaria that is resistant to artemisinin combination therapy.

[0071] Pharmaceutical Compositions The compounds of formula (I) and their pharma- ceutically acceptable salts and stereoisomers are usually, but not necessarily, formulated into pharmaceutical compositions prior to administration to a patient. Thus, in another aspect, there is provided a pharmaceutical formulation comprising: (a) a compound of formula I, or a pharma- ceutically acceptable salt or stereoisomer thereof; and (b) a pharma- ceutically acceptable excipient or carrier.

[0072] Suitable pharma- ceutically acceptable excipients include types of excipients such as binders, disintegrants, lubricants, glidants, granulating agents, coating agents, wetting agents, solvents, cosolvents, suspending agents, emulsifiers, sweeteners, flavoring agents, flavor masking agents, colorants, anti-caking agents, humectants, chelating agents, plasticizers, viscosity-increasing agents, antioxidants, preservatives, stabilizers, surfactants, and buffers. Those skilled in the art will appreciate that a particular pharma- ceutically acceptable excipient may serve multiple functions, and may serve alternative functions, depending on the amount of the excipient present in the formulation and the other components present in the formulation. A carrier excipient must be "acceptable" in the sense of being compatible with the other components of the formulation and not harmful to the recipient. Those skilled in the art have the knowledge and skill in the art to be able to select appropriate pharma- ceutical acceptable excipients in appropriate amounts for use in the present invention. Additionally, there are numerous resources available to those skilled in the art that describe pharma- ceutical acceptable excipients and may aid in selecting appropriate pharma- ceutical acceptable excipients. Examples include Remington's Pharmaceutical Sciences (Mack Publishing Company), The Handbook of Pharmaceutical Additives (Gower Publishing Limited), and The Handbook of Pharmaceutical Excipients (the American Pharmaceutical Association and the Pharmaceutical Press).

[0073] The pharmaceutical compositions of the present invention are prepared using techniques and methods known to those skilled in the art. Some of the methods commonly used in the art are described in Remington's Pharmaceutical Sciences (Mack Publishing Company). For example, dosage forms include: (1) oral administration, such as tablets, capsules, caplets, pills, lozenges, powders, syrups, elixirs, suspensions, solutions, emulsions, sachets, and cachets; (2) parenteral administration, such as sterile solutions, suspensions, and powders for reconstitution; (3) transdermal administration, such as transdermal patches; (4) rectal administration, such as suppositories; and (5) suitable for inhalation, such as aerosols and solutions.

[0074] In one aspect, the present invention relates to solid or liquid oral dosage forms, such as liquids, tablets, lozenges, or capsules, comprising a safe and effective amount of the compound of the present invention and a carrier. The carrier may be in the form of a diluent or filler. Suitable diluents and fillers generally include lactose, sucrose, dextrose, mannitol, sorbitol, starch (e.g., corn starch, potato starch, pregelatinized starch), cellulose and its derivatives (e.g., microcrystalline cellulose), calcium sulfate, and dibasic calcium phosphate. Liquid dosage forms are usually composed of a suspension or solution of the compound or a pharma- ceutically acceptable salt or stereoisomer in a liquid carrier, such as, for example, ethanol, olive oil, glycerin, glucose (syrup), or water (e.g., with the addition of flavors, suspending agents, colorants). When the composition is in the form of a tablet or lozenge, any pharmaceutical carrier routinely used to prepare solid dosage forms can be used. Examples of such carriers include magnesium stearate, terra alba, talc, gelatin, gum acacia, stearic acid, starch, lactose, sucrose, etc. If the composition is in the form of a capsule, any conventional encapsulation is suitable, such as using the above-mentioned carriers, or semi-solids (e.g., monodiglyceride of capric acid, Gelucire and Labrasol), or hard capsule shells (e.g., gelatin). If the composition is in the form of a soft-shell capsule, such as gelatin, any pharmaceutical carrier that is routinely used to prepare dispersions or suspensions, such as aqueous gums or oils, can be considered and incorporated into the soft capsule shell.

[0075] The pharmaceutical composition may be administered by any suitable route, for example, oral (including buccal or sublingual), inhalation, intranasal, topical (including buccal, sublingual or transdermal), parenteral (including subcutaneous, intramuscular, intravenous or intradermal) routes. In particular, the pharmaceutical composition is administered by oral administration route. The pharmaceutical composition may be provided in unit dosage form, containing a predetermined amount of active ingredient per unit dosage. In one embodiment, the unit dosage composition contains a daily dose or daily unit sub-dose, or a suitable fraction thereof, of the active ingredient. Thus, such a unit dosage may be administered multiple times per day. In one embodiment, the unit dosage composition contains a daily dose or daily unit sub-dose (if administered more than once per day), or a suitable fraction thereof, of the active ingredient, as described above.

[0076] The oral solid dosage form may further comprise an excipient in the form of a binder. Suitable binders include starch (e.g., corn starch, potato starch, pregelatinized starch), gelatin, gum acacia, sodium alginate, alginic acid, tragacanth, guar gum, povidone, cellulose and its derivatives (e.g., microcrystalline cellulose). The oral solid dosage form may further comprise an excipient in the form of a disintegrant. Suitable disintegrants include crospovidone, sodium starch glycolate, croscarmelose, alginic acid, and sodium carboxymethylcellulose. The oral solid dosage form may further comprise an excipient in the form of a lubricant. Examples of lubricants include stearic acid, magnesium stearate, calcium stearate, and talc.

[0077] In one embodiment, the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer is prepared for injection by intramuscular or subcutaneous injection. In one aspect, the present invention relates to an injectable composition comprising the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer. Standard formulation and manufacturing techniques can be used to prepare a suitable stable sterile injectable vehicle comprising the compound of formula (I) of the present invention or its pharmaceutically acceptable salt or stereoisomer. In some aspects, the injectable pharmaceutical composition is a long-acting injectable composition and provides a controlled release of the compound of formula (I) or its pharmaceutically acceptable salt or stereoisomer.

[0078] In one embodiment, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof is prepared for administration by injection, the composition comprising the compound and a pharma- ceutically acceptable excipient or carrier, such as Tween 20, PEG 400, and / or mannitol. In one embodiment, the compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof is formulated with Tween 20, PEG 400, and mannitol, suitable as a long-acting injectable composition.

[0079] combination When the compounds of formula (I) or pharma- ceutically acceptable salts or stereoisomers thereof are used for the treatment of malaria or Plasmodium falciparum, they may be used alone or in combination with at least one other therapeutic agent, such as at least one other antiparasitic agent, e.g. an antimalarial agent.

[0080] Thus, the present invention provides a combination of (a) a compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof; and (b) at least one other antimalarial agent. In one embodiment, the combination comprises one, two, or three additional antimalarial agents. For the avoidance of doubt, the at least one other antimalarial agent is not a compound of formula (I).

[0081] At least one other antimalarial agent is an investigational agent approved or recommended for the treatment of malaria.

[0082] The at least one other antimalarial agent may be selected from chloroquine, mefloquine, primaquine, pyrimethamine, quinine, artemisinin, halofantrine, doxycycline, amodiaquine, atovaquone, tafenoquine, dapsone, proguanil, sulfadoxine, cycloguanil, fansidar, piperaquine, lumefantrine, artesunate, dihydroartemisinin, artemether, fosmidomycin, and azithromycin.

[0083] In one embodiment, the at least one other antimalarial agent is an artemisinin agent.

[0084] The at least one other antimalarial agent may be tafenoquine.

[0085] In one embodiment, the additional antimalarial agents are atovaquone and proguanil. The at least one other antimalarial agent may be selected from ferroquine, KAF156, cypargamine, DSM265, artemisone, artemisinin, artefenomel, MMV048, SJ733, P218, MMV253, PA92, DDD498, AN13762, DSM421, UCT947, ACT451840, 6-chloro-7-methoxy-2-methyl-3-{4-[4-(trifluoromethoxy)phenoxy]phenyl}quinolin-4(1H)-one, 6-chloro-7-methoxy-2-methyl-3-(4-(4-(trifluoromethoxy)phenoxy)phenyl)quinolin-4(1H)-one, pharmaceutical salts thereof, and combinations thereof. In one embodiment, the additional antimalarial agent is 6-chloro-7-methoxy-2-methyl-3-{4-[4-(trifluoromethoxy)phenoxy]phenyl}quinolin-4(1H)-one, 6-chloro-7-methoxy-2-methyl-3-(4-(4-(trifluoromethoxy)phenoxy)phenyl)quinolin-4(1H)-one, a pharmaceutical salt thereof, or a combination thereof.

[0086] The at least one other antimalarial agent may be selected from OZ609, OZ277, and SAR97276.

[0087] In treating a Plasmodium falciparum infection, the at least one, two, or three additional antimalarial agents are selected as follows, wherein at least one of the antimalarial agents is an artemisinin-based agent. Artemether + lumefantrine Artesunate + Amodiaquine Artesunate + Mefloquine Dihydroartemisinin + Piperaquine Artesunate + Sulfadoxine-Pyrimethamine (SP) The above combination therapies are known as artemisinin-based combination therapies (ACTs). The choice of ACT is usually based on the results of therapeutic efficacy studies against local strains of Plasmodium falciparum malaria.

[0088] In the treatment of Plasmodium vivax infections, ACTs may be used as described above. Alternatively, the at least one other antimalarial drug may be chloroquine, especially in areas where chloroquine-resistant Plasmodium vivax does not exist. In areas where resistant Plasmodium vivax is identified, the infection may be treated with ACTs as described above.

[0089] These combinations can be conveniently provided for use in the form of pharmaceutical compositions or preparations.Therefore, also contemplated herein is a pharmaceutical composition comprising (a) the compound of formula (I) as described herein or its pharmaceutically acceptable salt or stereoisomer, (b) at least one other antimalarial agent, and (c) one or more pharmaceutically acceptable excipients as described herein.

[0090] The compound of formula (I) or a pharma- ceutically acceptable salt or stereoisomer thereof and the at least one other therapeutic agent may be administered together or separately, and when administered separately, this may be done separately or sequentially in any order (by the same or different routes of administration).

[0091] Dosage The relative amounts and timings of administration of the compound of the invention or a pharma- ceutically acceptable salt or stereoisomer thereof and the additional therapeutically active agent(s) will be selected in order to achieve the desired combined therapeutic effect and can be determined according to the judgment of a medical practitioner.

[0092] Typical amounts administered are from about 0.1 mg to about 1000 mg, and in some embodiments, from about 0.1 mg to about 500 mg. In one embodiment, the compound of formula (1) or a pharma- ceutically acceptable salt or stereoisomer thereof is administered in an amount of 200 mg.

[0093] The compounds of the present invention can be administered in doses ranging from, for example, 0.1 to 5000 mg, or 1 to 1500 mg, 2 to 800 mg, or 5 to 500 mg, for example, 2 to 200 mg or 10 to 1000 mg, examples of specific doses include 10, 20, 50, 80 mg, and 350 mg.

[0094] In one embodiment, the therapeutically effective single dose of the compound of formula (1) is about 10 to about 150 mg once a day for three consecutive days. In one embodiment, the compound of formula (1) or a pharma- ceutically acceptable salt or stereoisomer thereof is administered in an amount of about 50 mg to about 85 mg once a day for three consecutive days. In one embodiment, the compound of formula (1) or a pharma-ceutically acceptable salt or stereoisomer thereof is administered in an amount of about 10 mg to about 50 mg once a day for three consecutive days.

[0095] In one embodiment, the compound selected from the group consisting of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, and N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, or a pharma- ceutical acceptable salt or stereoisomer thereof, is administered in an amount of about 0.1 mg to 1000 mg. In one embodiment, the compound selected from the group consisting of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, and N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, or a pharma- ceutical acceptable salt or stereoisomer thereof is administered in an amount of about 200 mg.

[0096] Ultimately, however, the amount of compound administered and type of composition used will be left to the discretion of the physician, depending on the nature of the disease or physiological condition being treated.

[0097] Determination of effective dosages in this context is usually based on animal model studies followed by human clinical trials, following a dosing protocol that significantly reduces the occurrence or severity of the target disease symptoms or conditions in humans. Suitable models in this regard include, for example, mice, rats, birds, pigs, cats, non-human primates, and other recognized animal model subjects known in the art. Alternatively, effective dosages can be determined using in vitro models (e.g., whole cell assays that monitor the effect of various agents on the growth rate of parasites). Using such models, only routine calculations and adjustments are required to determine the appropriate concentration and dosage for administering a therapeutically effective amount of the compound (e.g., an amount effective to induce a desired immune response or to alleviate one or more symptoms of the target disease).

[0098] General synthesis route The compounds of the present invention can be prepared by various methods, including methods conventionally known in the chemical arts.Previously defined variables continue to have previously defined meanings unless otherwise indicated.Exemplary general synthetic methods are shown in the following schemes and can be easily adapted to prepare the compounds of the present invention.Specific compounds prepared according to the experimental procedures are disclosed in the Examples section.

[0099] [ka] Steps 1 and 2 are Suzuki coupling reactions which can be carried out using a suitable boronic acid or ester in the presence of a suitable catalyst such as PdCl2(dppf) and a base such as sodium carbonate in a suitable solvent such as isopropanol / water at a suitable temperature such as 120 °C.

[0100] Step 3 is a deesterification reaction that can be carried out using appropriate conditions such as LiOH·H2O in a suitable solvent mixture such as THF / H2O.

[0101] Step 4 is a coupling reaction using a suitable acid intermediate and the corresponding amine as coupling partners in the presence of a coupling agent such as HATU, in the presence of a base such as DIPEA, in a suitable solvent such as DMF.

[0102] Step 5: is deprotection, which can be carried out with a suitable acid such as 4M HCl in 1,4-dioxane. EXAMPLES

[0103] The present invention is further illustrated by the following non-limiting examples. Although specific embodiments of the present invention are described, those skilled in the art will understand that various changes and modifications can be made. Reference to preparations carried out in a manner similar to other preparations, or in a manner common to other preparations, may include variations in routine parameters, such as slight changes in time, temperature, post-treatment conditions, and amounts of reagents.

[0104] In some of the intermediates and examples below, starting materials are identified by reference to other intermediate or example numbers. This does not imply that the actual material from that particular intermediate or example was necessarily used in the subsequent step illustrated herein, but is used as a shorthand means to indicate the compound involved.

[0105] When materials are commercially available, they are indicated in capital letters in parentheses after the compound name. Commercially available reagents and solvents were used as received. All solvents used in the reactions were of high purity grade or anhydrous grade. Proton nuclear magnetic resonance ( 1 H NMR spectra were recorded and chemical shifts are reported in parts per million (δ) downfield from the internal standard tetramethylsilane (TMS). Abbreviations for NMR data are as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, dd = double doublet, dt = double triplet, app = apparent, br = broad. Mass spectra were obtained using electrospray (ES) ionization techniques. All temperatures are reported in degrees Celsius.

[0106] Where diastereomers are represented and the absolute stereochemistry is known, the stereocenter, i.e., the chiral carbon atom, is labelled with R or S.

[0107] Abbreviation AcOEt Ethyl acetate ACN Acetonitrile CDCl3 Deuterated Chloroform DCM Dichloromethane DIPEA N,N-Diisopropylethylamine DMF Dimethylformamide DMSO Dimethyl sulfoxide EtOH Ethanol h hour(s) HATU Azabenzotriazole tetramethyluronium hexafluorophosphate HCl Hydrochloric acid HPLC High Performance Liquid Chromatography i-PrOH Isopropyl alcohol K2CO3 Potassium Carbonate min MeOH Methanol NaOH Sodium hydroxide Na2CO3 Sodium Carbonate NH4Cl Ammonium chloride RBF Round Bottom Flask Rt room temperature SiO2 Silicon Dioxide TBME or tBuOMe tert-butyl methyl ether TFA Trifluoroacetic acid

[0108] Intermediate 1: Methyl 4-(6-chloropyrazin-2-yl)benzoate [ka] To a 100 mL RBF, (4-(methoxycarbonyl)phenyl)boronic acid (Apollo Scientific, 1.0 g, 5.56 mmol), 2,6-dichloropyrazine (Combi-Blocks, 1.656 g, 11.11 mmol), and K2CO3 (Chempure, 2.304 g, 16.67 mmol) were added at room temperature. Then, 1,2-dimethoxyethane (30.0 mL) and water (10.0 mL) were added at the same temperature. Then, the resulting reaction mixture was degassed with nitrogen for 15 minutes, followed by the addition of PdCl2(dppf)-CH2Cl2 adduct (Chempure, 0.159 g, 0.194 mmol) at room temperature. The reaction mixture was heated to 65° C. and stirred at the same temperature for 16 hours. The reaction mixture was diluted with water (10 mL) and extracted with ethyl acetate (2×25 mL). The combined organic phase was dried over Na2SO4 (5 g), filtered, and the filtrate was concentrated under reduced pressure to give a crude black solid.

[0109] The crude product was dissolved in 15 mL of DCM, adsorbed onto 10 g of silica gel (230-400 mesh) and purified by Biotage isolera column chromatography (silica gel 230-400 mesh, 40 g snap, flow rate 30 mL / min). The desired compound was eluted with 0-15% ethyl acetate in petroleum ether, and the collected fractions were pooled and concentrated under reduced pressure to give the title compound (900 mg, 3.59 mmol, 64.5% yield) as a white solid.

[0110] 1 H NMR(δ,ppm,CDCl3):9.38(s,1H),8.84(s,1H),8.29(d,2H),8.12(d,2H),3.91(s,3H). [ES MS] m / z:249(MH + ).

[0111] Intermediate 2: Methyl 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoate [ka] To a 10000 mL RBF, methyl 4-(6-chloropyrazine)benzoate (250 g, 1005 mmol), (5-fluoropyridin-3-yl)boronic acid (COMBI-BLOCKS, 156 g, 1106 mmol), and K2CO3 (Chempure, 417 g, 3016 mmol) were added at room temperature. Then, 1,4-dioxane (5000 mL) and water (1500.0 mL) were added at the same temperature. The resulting reaction mixture was degassed with nitrogen for 15 minutes, followed by the addition of PdCl2(dppf)-CH2Cl2 adduct (Chempure, 28.7 g, 35.2 mmol) at room temperature. The reaction mixture was heated to 55° C. and stirred at the same temperature for 3 hours. The reaction mixture was allowed to warm to room temperature and kept at the same temperature for 4 hours, at which time a solid precipitated out. The solid was filtered, washed with water (2000 mL), acetone (2500 mL), followed by petroleum ether (1500 mL) and dried under reduced pressure to give methyl 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoate (280.0 g, 897 mmol, 89% yield) as a white solid.

[0112] 1 H NMR(δ,ppm,DMSO-D6):9.44(s,1H),9.42(s,1H),9.37(s,1H),8.77(d,1H),8.65-8.55(m,1H),8.48(d,2H),8.15(d,2H),3.92(s,3H). [ES MS] m / z:310(MH + ).

[0113] Intermediate 3: 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoic acid [ka] To a stirred solution of methyl 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoate (200.0 g, 647 mmol) in tetrahydrofuran (2500 mL) was added lithium hydroxide monohydrate (Chempure, 81 g, 1940 mmol) in water (1000 mL) at room temperature. The resulting reaction mixture was stirred at room temperature for 12 hours. The reaction mixture was concentrated under reduced pressure to give the crude product as a white solid. The crude product was diluted with water (500 mL) and the pH was adjusted to 3-4 using 1.5 N HCl (550 mL) to precipitate a white solid. The resulting reaction mixture was stirred for 15 minutes and the resulting solid was filtered, washed with water (2500 mL), followed by acetone (1500 mL) and dried under reduced pressure to give the title compound (187 g, 632 mmol, 98% yield) as a white solid.

[0114] 1 H NMR(δ,ppm,DMSO-D6):13.21(bs,1H),9.43(s,1H),9.42(s,1H),9.38(t,1H),8.77(d,1H),8.62-8.58(m,1H),8.45(d,2H),8.13(d,2H). [ES MS] m / z:296(MH + ).

[0115] Intermediate 4: tert-Butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclobutyl)carbamate [ka] To a suspension of 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoic acid (20 g, 67.7 mmol) and DIPEA (ALDRICH, 59.2 ml, 339 mmol) in N,N-dimethylformamide (DMF) (300 ml) was added HATU (FLUOROCHEM, 33.5 g, 88 mmol) (did not dissolve after stirring for 10 min). Neat powdered tert-butyl (1-(aminomethyl)cyclobutyl)carbamate (ENAMINE, 16.28 g, 81 mmol) was added and the resulting mixture was stirred at room temperature.

[0116] The reaction was diluted with AcOEt (100 ml) and 1N NH4Cl was added until complete precipitation of the white solid (500 ml). The mixture was filtered and rinsed with water (2 x 100 ml). The solid was dried under vacuum to give the title compound (31 g, 64.9 mmol, 96%) as a white solid.

[0117] 1 H NMR(δ,ppm,CDCl3):9.42(d,1H),9.38(t,1H),8.77(d,1H),8.63-8.57(m,1H),8.43(d,2H),8.05(d,2H),7.01(br s,1H),3.58(d,2H),2.35-2.20(m,2H),2.13-2.01(m,2H),1.87-1.85(m,2H),1.40(s,9H). [ES MS] m / z:478(MH + ).

[0118] Example 1: N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, ditrifluoroacetate [ka] To a solution of tert-butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclobutyl)carbamate (50 mg, 0.105 mmol) in dry dichloromethane (2 mL) under N2 atmosphere was added trifluoroacetic acid (1.000 mL) and the resulting mixture was stirred at room temperature. After 30 min, the reaction was diluted with DCM and concentrated under reduced pressure. The resulting crude product was purified by preparative HPLC (sample loaded in 1.5 mL MeOH, XBridge 19×150 mm, flow rate 17 mL / min, using ACN and HO with 0.1% TFA as mobile phase) to give, after collection and lyophilization of appropriate fractions, 35 mg of aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, ditrifluoroacetate (35 mg, 0.058 mmol, 55.2% yield) as a white solid.

[0119] 1 H NMR(δ,ppm,DMSO- d6):9.43(d,1H),9.39-9.36(m,1H),8.95-8.88(m,1H),8.78(d,1H),8.65-8.56(m,1H),8.4 6(d,2H),8.10(d,2H),8.07-7.98(m,2H),3.67(d,2H),2.28-2.10(m,4H),1.99-1.76(m,2H). [ES MS] m / z: 378(MH + ).

[0120] Example 2: N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, dihydrochloride [ka] To a suspension of tert-butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclobutyl)carbamate (100 mg, 0.209 mmol) in anhydrous 1-propanol (2 mL) under N2 atmosphere, 6N hydrochloric acid in iPrOH (FLUOROCHEM, 2 mL, 12.00 mmol) was added and the resulting mixture was stirred at room temperature. After 2 h, TBME was added and the resulting suspension was concentrated to give a cream solid. This solid was treated with ACN, filtered and washed three times. The solid was dried under a stream of air to give the title compound (80 mg, 0.178 mmol, 85% yield) as a cream solid.

[0121] 1 H NMR(δ,ppm,DMSO-d6):9.42(d,2H),9,9.38(s,1H),9.06(t,1H),8.77(d,1H),8.66-8.57(m,1H) ,8.44(d,2H),8.33(br.s,2H),8.17(d,2H),3.70(d,2H),2.29-2.14(m,4H),1.99-1.77(m,2H). [ES MS] m / z: 378(MH + ).

[0122] Example 3: N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, sulfate [ka] To a solution of tert-butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclobutyl)carbamate (100 mg, 0.209 mmol) in dichloromethane (DCM) (0.5 mL) and methanol (0.5 mL) at 40° C. was added sulfuric acid (0.1 mL, 1.876 mmol) dropwise and the reaction was stirred at 40° C. The reaction was allowed to warm to room temperature, tBuOMe was added, and the solid was filtered, rinsed with tBuOMe (2 times), and dried under a stream of nitrogen to give an off-white solid (125 mg, N74910-88-1).

[0123] 1 H NMR(δ,ppm,DMSO- d6): 9.44(s,1H),9.43(s,1H),9.39(t,1H),8.92(t,1H),8.79(d,1H),8.66-8.58(m,1H),8.49-8.45( m,2H),8.13-8.08(m,2H),8.06-7.94(m,3H),3.67(d,2H),2.27-2.11(m,4H),1.97-1.77(m,2H). [ES MS] m / z: 378(MH+).

[0124] Example 4: N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] To a suspension of tert-butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclobutyl)carbamate (74.27 g, 156 mmol) in dichloromethane (1 L) at room temperature, TFA (150 ml, 1947 mmol) was added dropwise over 30 minutes (to dissolve) and the reaction was stirred at room temperature. After 16 hours, water (1 L) was added and stirred for 15 minutes, the organic phase was separated and the aqueous phase was made basic with saturated Na2CO3 solution to reveal a yellow solid. The yellow solid was extracted with a mixture of DCM / MeOH 10% (3 x 700 ml). The combined organic phases were washed with saturated NaCl and concentrated in vacuo to give a yellow solid. This was triturated with EtOH (50 ml), filtered, rinsed with EtOH (25 ml) and dried to give the title compound (51 g, 135 mmol, 87%) as a yellowish crystalline solid.

[0125] 1 H NMR(δ,ppm,DMSO-D6):9.41(d,2H),9.37(t,1H),8.77(d,1H),8.62-8.57(m,1H),8.48- 8.38(m,3H),8.06(d,2H),3.41(d,2H),2.03(m,2H),1.89(s,2H),1.82-1.54(m,4H)[ES MS] m / z:378(MH + ).

[0126] Example 4a: Preparation of crystalline forms of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide The X-ray powder diffraction (XRPD) pattern of the crystalline form obtained in Example 4 is shown in FIG. 1 and a summary of the diffraction angles is given in Table 1 below. XRPD analysis was performed on a PANalytical Empyrean powder diffractometer, model 9430 060 03001, using a PIXcel3D detector. Acquisition conditions were: radiation: Cu Kα, generator voltage: 45 kV, generator current: 40 mA, start angle: 2.0° 2θ, end angle: 40.0° 2θ, step size: 0.0263° 2θ, time per step: 46.665 seconds. Samples were prepared by mounting a few milligrams of sample onto a silicon wafer (zero background plate) to create a thin powder layer. The margin of error is approximately ±0.1° 2θ for each peak assignment. Peak intensities may vary from sample to sample due to preferred orientation.

[0127] [Table 1]

[0128] Intermediate 5: tert-Butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclopropyl)carbamate [ka] To a solution of 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoic acid (300 mg, 1.016 mmol), tert-butyl (1-(aminomethyl)cyclopropyl)carbamate (Combi-Blocks, 246 mg, 1.321 mmol), and DIPEA (Sigma-Aldrich, 0.532 mL, 3.05 mmol) in N,N-dimethylformamide (DMF) (10 mL) was added HATU (Fluorochem, 541 mg, 1.422 mmol) under N2 atmosphere and the resulting mixture was stirred at room temperature.

[0129] After 15.5 h, water was added to completely precipitate a pale yellow solid (25 mL). The solid was washed successively with 0.5 M NaOH (25 mL) and water (2 x 25 mL), then dried under airflow. The solid (450 mg) was loaded onto a chromatography column ( Purification on 3 g SiO2, solid load on 27 g SiO2, Silicycle, Cy:EtOAc gradient from 80:20 to 0:100 in 30 min, flow rate 30 mL / min) afforded the title compound (358 mg, 0.772 mmol, 76% yield) as a white solid after collection and drying of appropriate fractions.

[0130] 1 H NMR(δ,ppm,DMSO-d6):9.41(s,1H),9.40(s,1H),9.37(t,1H),8.77(d,1H),8.63-8.56(m,1H),8.52(t,1 H),8.45-8.39(m,2H),8.04(br.d,2H),7.26(s,1H),3.43(d,2H),0.83-0.76(m,2H),0.67-0.61(m,2H). [ES MS] m / z:464(MH + ).

[0131] Example 5: N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, dihydrochloride [ka] To a stirred solution of tert-butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclopropyl)carbamate (100 mg, 0.216 mmol) in dichloromethane (2 mL) was added HCl in 1,4-dioxane (SYMAX LABORATORY, 4N, 0.162 mL, 0.647 mmol) at 0° C. The reaction mixture was stirred at room temperature for 1 h.

[0132] The reaction mixture was diluted with DCM (5 mL) and excess solvent was concentrated under reduced pressure to give the crude product as a brown solid. The crude product was triturated with diethyl ether (3×10 mL) and the supernatant was decanted. The compound was then dried under reduced pressure to give the title compound (73 mg, 0.180 mmol, 77%) as a brown solid.

[0133] 1 H NMR(δ,ppm,DMSO-d6):9.44(s,1H),9.42(s,1H),9.39(m,1H),8.97(t,1H),8.79(d,1H),8.62(m,1H),8.46(d,2H),8.33(br s,3H),8.13(d,2H),3.58(br d,2H),0.93(s,4H). [ES MS] m / z: 364(MH+).

[0134] Example 6: N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, difluoroacetate [ka] tert-Butyl (1-((4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)methyl)cyclopropyl)carbamate (358 mg, 0.772 mmol) was dissolved in trifluoroacetic acid (5 mL) at 0° C. and the reaction was allowed to warm to room temperature. After 14 h, the reaction was concentrated under reduced pressure. The residue (500 mg) was dissolved in 3.6 mL of MeOH and purified by preparative HPLC (Column: X-Bridge (50 mm×150 mm), gradient: water (0.1% TFA):acetonitrile (0.1% TFA) 20% to 100% to 100% (8 min), single injection, flow rate: 80 ml / min). Fractions containing the product were collected and the solvent was evaporated under vacuum to give 300 mg fraction 1 and 155 mg fraction 2 as colorless oils.

[0135] - Fraction 1 was suspended in ACN (10 mL) and water (10 mL) and lyophilized to give the title compound (285 mg, 0.482 mmol, 62.4% yield) as a white solid.

[0136] - Fraction 2 was suspended in ACN (10 mL) and water (10 mL) and lyophilized to give the title compound (155 mg, 0.262 mmol, 33.9% yield) as a white solid with low purity (95% purity by HPLC).

[0137] 1 H NMR(δ,ppm,DMSO-D6):9.43(s,1H),9.42(s,1H),9.38(t,1H),8.88(t,1H),8.78(d,1H),8.61(m,1H),8.45(m,2H),8.21(br s,3H),8.08(m,2H),3.58(d,2H),0.91(m,4H). [ES MS] m / z: 364(MH+).

[0138] Intermediate 6: tert-Butyl (1-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)-2-methylpropan-2-yl)carbamate [ka] To a solution of 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoic acid (187 mg, 0.633 mmol) and DIPEA (SIGMA-ALDRICH, 0.553 mL, 3.17 mmol) in N,N-dimethylformamide (6.5 mL) was added HATU (FLUOROCHEM, 313 mg, 0.823 mmol). After stirring for 10 min, tert-butyl (1-amino-2-methylpropan-2-yl)carbamate (COMBI-BLOCKS, 155 mg, 0.823 mmol) was added and the resulting mixture was stirred at room temperature.

[0139] After 16.5 h, the reaction was partitioned between 20 mL of 1N NH4Cl and 50 mL of ethyl acetate. The layers were separated and the organics were washed with 1N NH4Cl (20 mL) and then with brine (20 mL). The resulting mixture was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by chromatography column (loaded with 1.5 mL of DCM, 12 g of SiO2, silicycle, gradient of Cy:EtOAc-EtOH3 / 1 from 100:0 to 85:15 to 50:50) to give, after collection and concentration of the appropriate fractions, 250 mg of tert-butyl (1-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)-2-methylpropan-2-yl)carbamate as a white solid (250 mg, 0.537 mmol, 85% yield).

[0140] 1 H NMR(δ,ppm,DMSO-d6):9.41(d,2H),9.37(t,1H),8.77(d,1H),8.64(t,1H),8.62-8.57(m,1H) ,8.42(d,2H),8.04(d,2H),1H),6.61(br.s,1H),3.42(d,2H),1.45-1.34(m,9H),1.26(s,6H). [ES MS] m / z: 466(MH + ).

[0141] Example 7: N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, difluoroacetate [ka] To a solution of tert-butyl (1-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)-2-methylpropan-2-yl)carbamate (295 mg, 0.634 mmol) in dry dichloromethane (2 mL) under a N2 atmosphere, trifluoroacetic acid (1.000 mL) was added and the resulting mixture was stirred at room temperature.

[0142] The reaction was diluted with MeOH and concentrated under reduced pressure. The residue was purified by preparative HPLC (sample loaded in 1.5 mL MeOH, XBridge 30×100 mm, ACN:HO (with 0.1% TFA) as mobile phase, flow rate 35 mL / min), collected and lyophilized to give 140 mg of N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, ditrifluoroacetate (140 mg, 0.292 mmol, 46.1% yield) as a white solid.

[0143] 1 H NMR(δ,ppm,DMSO-D6):9.42(d,2H),9.38(t,1H),8.88(t,1H),8.77(d,1H),8.63- 8.56(m,1H),8.48-8.41(m,2H),8.14-8.06(m,2H),7.89-7.73(m,1H),7.88-7.73(m,1H),3.53-3.40(m,2H),1.38-1.20(m,6H)[ES MS] m / z:366(MH + ).

[0144] Intermediate 7: tert-Butyl-((1R,2S)-2-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)cyclohexyl)carbamate [ka] To a solution of 4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzoic acid (350 mg, 1.185 mmol) in N,N-dimethylformamide (15 mL) was added DIPEA (Sonia, 0.621 mL, 3.56 mmol) and HATU (GLR, 676 mg, 1.778 mmol) at 0° C. The reaction mixture was stirred at 0° C. for 10 min. Then, tert-butyl ((1R,2S)-2-aminocyclohexyl)carbamate (TCI, 356 mg, 1.659 mmol) was added to the reaction. The reaction mixture was stirred at room temperature for 16 h. The reaction mixture was quenched with cold water (50 mL) and a white solid precipitated. The resulting solid was filtered, washed with cold water (50 mL) and dried under vacuum. The crude product was adsorbed onto neutral alumina (1 g) and purified by Isolera column chromatography (neutral alumina, 25 g snap) using 2% methanol in dichloromethane as eluent. Product fractions were pooled and evaporated in vacuo to give the title compound (430 mg, 0.865 mmol, 72.9% yield) as a brown solid.

[0145] 1 H NMR(δ,ppm,DMSO-d6):9.42(s,1H),9.41(s,1H),9.37(t,1H),8.77(d,1H),8.63-8-55(m,1H),8.41(d ,2H),8.00(br.s,3H),6.69(m,1H),4.08(m,1H),3.80(m,1H),1.78(m,2H),1.56(m,4H),1.32(m,11H). [ES MS] m / z:392 [(MH + )-100].

[0146] Example 8: N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, dihydrochloride [ka] A solution of tert-butyl ((1R,2S)-2-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)cyclohexyl)carbamate (0.895 g, 1.821 mmol) in a 1:9 mixture of DCM:MeOH (10 mL) was heated to 40 °C under a N2 atmosphere and 37% hydrochloric acid (Sigma-Aldrich, 1 mL, 12.18 mmol) was added in one portion. The resulting mixture (solution) was stirred at 40 °C overnight.

[0147] After 20 hours, the reaction was concentrated under reduced pressure. The resulting solid was triturated with TBME, but the solid that formed was not filterable. After concentration, the mixture was triturated with iPrOH, but the solid that formed was again not filterable.

[0148] After concentrating again, the mixture was dissolved in MeOH / DCM mixture and DCM was slowly evaporated on a rotary evaporator. The resulting suspension was stored in the refrigerator for 2 days. The suspension was filtered and washed with cold methanol. The resulting solid was dried under air stream to give 800 mg of N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide dihydrochloride (800 mg, 1.723 mmol, 95% yield) as a white solid.

[0149] 1 H NMR(δ,ppm,DMSO-d6):9.43(s,1H),9.41(s,1H),9.38(t,1H),8.78(d,1H),8.61(m,1H),8.42(d,2H),8.39(d,1H),8.17(d,2H),8.12(br [ES MS] m / z: 392 [(MH+)].

[0150] Example 9: N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, difluoroacetate [ka] To a suspension of N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide (850 mg, 2.171 mmol) in dichloromethane (DCM) (40 mL) was added trifluoroacetic acid (2 mL, 26.0 mmol) (became a solution) and stirred at room temperature for 1 h.

[0151] The crude product was concentrated in vacuo and the resulting solid was dried in a vacuum oven at 40° C. for 18 hours to give a yellowish solid, N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, ditrifluoroacetate salt (1.36 g, 2.195 mmol, approx. 99% yield).

[0152] 1 H NMR(δ,ppm,DMSO-d6):9.44(s,1H),9.42(s,1H),9.38(m,1H),8.78(d,1H),8.60(m,1H),8.43(d,2H),8.23(d,1H),8.12(d,2H),7.82(br d,3H),4.37(m,1H),3.45(m,1H),1.75(m,6H),1.42(m,2H). [ES MS] m / z: 392(MH + ).

[0153] Example 10: N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide [ka] To a solution of tert-butyl ((1R,2S)-2-(4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamido)cyclohexyl)carbamate (1.7 g, 3.46 mmol) in a mixture of dichloromethane (DCM) (5 mL) and methanol (5.00 mL), 6N hydrochloric acid in iPrOH (FLUOROCHEM, 1.32 mL, 7.92 mmol) was added and stirred at room temperature. After 16 h, the solid was filtered, the solid was suspended in water, saturated Na2CO3 solution was added until a basic pH was reached, the solid was extracted with DCM / MeOH 10% (3×10 ml), the organic phases were combined, washed with saturated NaCl solution, dried over Na2SO4, filtered and concentrated in vacuo to give a yellow crystalline solid N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide (1.02 g, 2.61 mmol, 75% yield).

[0154] 1 H NMR(δ,ppm,DMSO-d6):9.41(s,2H),9.37(m,1H),8.77(d,1H),8.60(m,1H),8.40(d,2H) ),8.03(d,2H),8.01(d,1H),3.95(m,1H),3.06(m,1H),1.84-1.46(m,8H),1.32(m,2H). [ES MS] m / z: 392(MH + ).

[0155] Example 10a: Crystalline form of N-((1S,2R)-2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide The X-ray powder diffraction (XRPD) pattern of the crystalline form obtained in Example 11 is shown in FIG. 3, and a summary of the diffraction angles is given in Table 2 below. XRPD analysis was performed on a PANalytical Empyrean powder diffractometer, model 9430 060 03001, using a PIXcel3D detector. Acquisition conditions were: radiation: Cu Kα, generator voltage: 45 kV, generator current: 40 mA, start angle: 2.0° 2θ, end angle: 40.0° 2θ, step size: 0.0263° 2θ, time per step: 46.665 seconds. Samples were prepared by mounting a few milligrams of sample onto a silicon wafer (zero background plate) to create a thin powder layer. The margin of error is approximately ±0.1° 2θ for each peak assignment. Peak intensities may vary from sample to sample due to preferred orientation.

[0156] [Table 2]

[0157] Biological and physicochemical data The compounds of the present invention can be tested in one of several biological and physicochemical assays to determine the concentration of compound required to provide a given pharmacological effect, which assays are described below.

[0158] In vitro efficacy P.falciparum growth inhibition assay Sybr green Parasite growth is determined by measuring staining of the minor groove of DNA with SYBR Green I, which labels any remaining parasites. Parasite growth is determined by measuring staining of the minor groove of DNA with SYBR Green I, which labels any remaining parasites. The DNA-SYBR complex absorbs light that peaks at λ = 498 nm and emits light that peaks at λ = 522 nm.

[0159] methodology Briefly, cultures of red blood cells (RBCs) parasitized with strain 3D7A (0.5% parasitemia and 2% hematocrit in RPMI-1640 supplemented with 25 ml of Albumax per 500 ml and 150 mM hypoxanthine) are exposed to 3-fold serial dilutions of compounds. Plates are incubated for 48 h at 37°C, 5% CO2, 5% O2, 90% N2. After 48 h of incubation, SyberGreen I solution (2x) is added and plates are incubated for 30 min at 37°C, 5% CO2, 5% O2, 90% N2, then plates are frozen at -80°C. Plates are then read in EnVision (EnVision Multilabel Plate Reader, Perkin Elmer). Data (pIC50) are generated by ActivityBase (IDBS) and graphs are checked by Spotfire.

[0160] result The results are shown below in Table 3. Inhibition of parasite growth in the in vitro whole cell assay (infected erythrocytes) directly correlates with a reduction in parasitemia in vivo.

[0161] [Table 3]

[0162] In vivo efficacy In vivo efficacy assay for P. falciparum.

[0163] Antimalarial in vivo efficacy was determined using a P. falciparum mouse model following the procedures described in the following publication: Jimenez-Diaz, MB, Mulet, T., Viera, S., Gomez, V., Garuti, H., Ibanez, J., Alvarez-Doval, A., Shlutz, DL, Martinez, A., Improved Murine Model Of Malaria Using Plasmodium falciparum(Competent Strains and Non-Myelodepleted NOD-scid IL2R_null Mice Engrafted with Human Erythrocytes) Antimicrob. Agents Chemother 2009,53(10),4533-4536.

[0164] result The aim of this study was to investigate the mechanism of NODscidlL2Ry mice transplanted with human erythrocytes. 0087 / N9 Plasmodium falciparum Pf3D7 growing in the peripheral blood of mice 0087 / N9 The objective of the study was to evaluate the therapeutic effect of the examples on inflammatory bowel disease. The levels of the examples were measured in serial peripheral blood samples obtained from each mouse in the efficacy study within the first 23 hours after the first dose. The area under the curve for the levels of the compound is used to estimate the exposure in the blood during the first 23 hours after the first dose (AUC 0-23h ).

[0165] P. falciparum Pf3D7 of Examples 1, 2, 5, 7, 8, and 10 0087 / N9 The effect on the immune system was assessed by microscopy and flow cytometry.

[0166] The results are shown in Table 4 below.

[0167] [Table 4]

[0168] Solubility evaluation in biorelevant media The equilibrium solubility of the compounds was measured at room temperature after equilibration in fasted simulated intestinal fluid (FaSSIF) at pH 6.5 for 4 hours.

[0169] Solvents and buffers HPLC grade organic solvents were used. Ultrapure water (Milli-Q grade) was used. Buffer solutions were prepared with ultrapure water.

[0170] procedure a) 1 mg of solid compound was weighed into a 4 mL glass vial and 1 mL of FaSSIF was added. b) 1 mg of the same solid was weighed into a 4 mL glass vial and 1 mL of dimethyl sulfoxide (DMSO) was added to make a standard solution of known concentration. c) The FaSSIF samples were left on a shaker (900 rpm) at room temperature for 4 hours. d) After 4 hours, the resulting suspension was transferred to a Multiscreen HTS-PCF 96-well solubility filter plate and the filtrate was separated from the remaining solids using vacuum filtration. e) The filtrate was analyzed by LC-UV. f) Three internal standards of known solubility (atovaquone, nimesulide and warfarin at 2, 20 and 140 mg / mL respectively) were tested alongside the compound in the same procedure to assess the suitability of the process.

[0171] LC-UV assay for analytical quantification Quantification of compound concentrations in the filtrate was performed by HPLC-UV using a single-point calibration of known concentrations of compound in DMSO. The dynamic range of the assay was 1-1000 g / ml.

[0172] Analyzing data Analysis of the LC-UV data was performed using an in-house Excel macro. The solubility (mg / mL) of each compound was calculated from the peak areas of the samples and standards.

[0173] result The results are shown in Table 5 below. The aqueous solubility of a compound is an important drug property that affects oral bioavailability. FaSSIF medium mimics the fluid of the intestinal region where most drugs are absorbed. Limited solubility of a drug in the intestinal tract can result in incomplete and variable absorption of the drug. It is therefore of interest to estimate the amount of drug dissolved in the digestive tract.

[0174] [Table 5]

[0175] Solubility assessment in aqueous buffers Dynamic aqueous solubility is measured at room temperature after equilibration for 1 h in aqueous phosphate buffered saline (PBS) at pH 7.4, and is determined by measuring the concentration of solute in solution after precipitation from a DMSO stock solution.

[0176] Solvents and buffers HPLC grade organic solvents were used. Ultrapure water (Milli-Q grade) was used. Buffer solutions were prepared with ultrapure water.

[0177] procedure 5 ml of the 10 mM DMSO stock solution was dispensed into wells of a Multiscreen HTS-PCF 96-well solubility filter plate and 95 ml of PBS was added. The sample plate was left to equilibrate at room temperature for 1 hour. The solution was filtered into a 96-well collection plate by vacuum filtration. The filtrate was analyzed by HPLC-CAD (charged aerosol detector). Calibration standards for ketoconazole and primidone were prepared by serial dilution in DMSO at concentrations ranging from 0.016 to 4.5 mg / ml, and calibration curves were generated.

[0178] LC-UV assay for analytical quantification Quantification of compound concentrations in the filtrate was performed by HPLC-CAD using sample peak areas and calibration factors from the CAD.

[0179] Analyzing data Analysis of the HPLC-CAD data was performed using an in-house Excel macro. The concentration (mM) and solubility (μg / ml) of each compound were calculated from the sample peak area and calibration factor.

[0180] result The results are shown in Table 6 below.

[0181] [Table 6]

Claims

1. Compounds of formula (I): 【Chemistry 1】 or a pharmaceutically acceptable salt or stereoisomer thereof, wherein R １ , R ２ , R ３ , and R ４ are each independently H, halo, or C １ -C ６ Alkyl, as well as O, S, SO, SO ２ , N.H., and N.C. １ -C ６ is selected from the group consisting of 3- to 7-membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of alkyl; or R １ and R ２ together with the atoms to which they are bonded, O, S, SO, SO ２ , N.H., and N.C. １ -C ６ forming a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of alkyl; R ３ and R ４ are each independently H, C １ -C ６ Alkyl, as well as O, S, SO, SO ２ , N.H., and N.C. １ -C ６ is selected from the group consisting of 3- to 7-membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of alkyl; or R １ and R ３ together with the atoms to which they are bonded, O, S, SO, SO ２ , N.H., and N.C. １ -C ６ forming a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring optionally containing a heteroatom selected from the group consisting of alkyl; R ２ and R ４ are each independently H, C １ -C ６ Alkyl, as well as O, S, SO, SO ２ , N.H., and N.C. １ -C ６ is selected from the group consisting of 3-7 membered cycloalkyl rings optionally containing a heteroatom selected from the group consisting of alkyl; R ５ is halo and C １ -C ６ alkyl).

2. R ５ 2. The compound of claim 1, or a pharmaceutically acceptable salt or stereoisomer thereof, wherein is halo.

3. R ５ 2. The compound of claim 1, or a pharmaceutically acceptable salt or stereoisomer thereof, wherein

4. R ３ and R ４ 10. The compound of claim 1, or a pharmaceutically acceptable salt or stereoisomer thereof, wherein each is H.

5. R １ and R ２ are taken together with the atoms to which they are both attached to form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring, or a pharmaceutically acceptable salt or stereoisomer thereof.

6. The compound is 【Chemistry 2】 2. The compound of claim 1, wherein:

7. 7. The compound of claim 6 in the form of a free base.

8. i) an X-ray powder diffraction pattern (XRPD) substantially as shown in Figure 1; and / or ii) has an X-ray powder diffraction pattern (XRPD) with specific peaks at 6.7, 11.2, 12.7, 13.4, 16.2, 16.6, 17.9, 20.9, 26.7, and 28.2 degrees 2θ (±0.1° 2θ experimental error); The compound of claim 7.

9. 7. The compound of claim 6 in the form of a pharmaceutically acceptable sulfate.

10. 7. The compound of claim 6 in the form of a pharmaceutically acceptable dihydrochloride salt.

11. 7. The compound of claim 6 in the form of a pharmaceutically acceptable ditrifluoroacetate salt.

12. The compound is 【Transformation 3】 2. The compound of claim 1, wherein:

13. R １ and R ２ are respectively, C １ -C ６ 2. The compound of claim 1, or a pharmaceutically acceptable salt or stereoisomer thereof, wherein:

14. The compound is 【Chemistry 4】 2. The compound of claim 1, wherein:

15. R １ and R ３ are taken together with the atoms to which they are both attached to form a 3-, 4-, 5-, 6-, or 7-membered cycloalkyl ring, or a pharmaceutically acceptable salt or stereoisomer thereof.

16. The compound is 【Transformation 5】 2. The compound of claim 1, wherein:

17. 17. The compound of claim 16 in the form of a free base.

18. i) an X-ray powder diffraction pattern (XRPD) substantially as shown in Figure 2; and / or ii) has an X-ray powder diffraction pattern (XRPD) with specific peaks at 5.4, 10.8, 15.3, 16.6, 18.2, 20.1, 21.8, 22.4, 28.1, and 31.7 degrees 2θ (±0.1° 2θ experimental error); 18. The compound of claim 17.

19. A compound, or a pharmaceutically acceptable salt or stereoisomer thereof, selected from the group consisting of N-((1-aminocyclobutyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-amino-2-methylpropyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, N-(2-aminocyclohexyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide, and N-((1-aminocyclopropyl)methyl)-4-(6-(5-fluoropyridin-3-yl)pyrazin-2-yl)benzamide.

20. A pharmaceutical composition comprising: (a) a compound according to any one of claims 1 to 19, or a pharmaceutically acceptable salt or stereoisomer thereof; and (b) a pharmaceutically acceptable excipient.

21. 21. A pharmaceutical composition according to claim 20 for use in the treatment of a parasitic protozoan infection.

22. The pharmaceutical composition of claim 21, wherein the parasitic protozoan infection is malaria.

23. 22. The pharmaceutical composition of claim 21, wherein the parasitic protozoan infection is Plasmodium falciparum.

24. A combination pharmaceutical comprising: (a) a compound according to any one of claims 1 to 19 or a pharmaceutically acceptable salt or stereoisomer thereof; and (b) at least one other antimalarial agent.

25. The combination pharmaceutical of claim 24 for treating a parasitic protozoan infection.

26. 26. The pharmaceutical combination of claim 25, wherein the parasitic protozoan infection is malaria.

27. 26. The pharmaceutical combination of claim 25, wherein the parasitic protozoan infection is Plasmodium falciparum.

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