WO2010142741A1

WO2010142741A1 - Phenylpyridylpyridones for use as antimalarial agents

Info

Publication number: WO2010142741A1
Application number: PCT/EP2010/058109
Authority: WO
Inventors: Jose Maria Bueno-Calderon; Jose Maria Fiandor-Roman
Original assignee: Glaxo Group Limited
Priority date: 2009-06-12
Filing date: 2010-06-09
Publication date: 2010-12-16

Abstract

4-Pyridone derivatives of Formula (I) wherein R¹, R², X and n are as defined in the description and pharmaceutically acceptable salts thereof, pharmaceutical formulations thereof and their use in chemotherapy of certain parasitic infections such as malaria, are provided.

Description

PHENYLPYRIDYLPYRIDONES FOR USE AS ANTIMALARIAL AGENTS

FIELD OF THE INVENTION

The invention relates to heterocyclic compounds and their use in chemotherapy. More specifically, this invention is concerned with certain 4-pyridone derivatives, processes for their preparation, pharmaceutical formulations thereof and their use in chemotherapy of certain parasitic infections such as malaria, and in particular infection by Plasmodium falciparum.

BACKGROUND OF THE INVENTION Parasitic protozoal infections are responsible for a wide variety of diseases of medical and veterinary importance, including malaria in man and various coccidioses in birds, fish and mammals. Many of the diseases are life-threatening to the host and cause considerable economic loss in animal husbandry, such as species of Eimeria, Theileήa, Babesia, Cryptosporidium, Toxoplasma (such as Toxoplasma brucei, African sleeping sickness and Toxoplasma cruzi, Chagas disease) and Plasmodium (such as Plasmodium falciparum), and the Mastigophora such as species of Leishmania (such as Leishmania donovani). Another parasitic organism of increasing concern is Pneumocytis carinii, which can cause an often fatal pneumonia in immunodeficient or immunocompromised hosts, including those infected with HIV.

Malaria is one of the major disease problems of the developing world. The most virulent malaria-causing parasite in humans is the parasite Plasmodium falciparum, which is the cause of hundreds of millions of cases of malaria per annum, and is thought to cause over 1 million deaths each year, Breman, J. G., et al., (2001 ) Am. Trop. Med. Hyg. 64, 1-1 1. One problem encountered in the treatment of malaria is the build-up of resistance by the parasite to available drugs. Thus, there is a need to develop new antimalarial drugs.

A problem encountered in the development of new drugs for the treatment of parasitic protozoal infections, such as malaria, is that good activity in the inhibition of parasitic target enzymes may be accompanied by a level of activity against human enzymes. For example, compounds that are active in the inhibition of electron transport chains in malarial parasites may also have inhibitory effect on respiration in humans. Thus, there is a need for antimalarial drugs with improved cytoxicity profiles that have good activity against parasitic target enzymes accompanied by low activity against human target enzymes. Although known 4-pyridone derivatives are selective inhibitors of the plasmodial cytochrome bd , they have shown some inhibitory activity in the mammalian enzyme. Therefore, compounds with low inhibitory capacity in the human cytochrome bd are needed.

Cases of uncomplicated malaria are conveniently treated by the enteral administration of an oral dosage form. However in severe cases of malaria it would be advantageous to administer a medicament parenterally, for example, by injection or infusion. PCT Patent Application No. WO 2006/094799 discloses a class of 4-pyridone derivatives which exhibit activity against protozoa, in particular against the malarial parasite Plasmodium falciparum. It has been found that compounds according to the present invention, generically disclosed in WO 2006/094799, and having a specific substitution pattern, exhibit improved properties over those compounds specifically disclosed in WO 2006/094799.

SUMMARY OF THE INVENTION

This invention is directed to certain 4-pyridone derivatives, processes for their preparation, pharmaceutical compositions comprising such compounds and use of the compounds in the chemotherapy of certain parasitic infections such as malaria, and in particular infection by Plasmodium falciparum.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a compound of Formula I:

wherein: each R¹ independently represents halo, CF₃ Or OCF₃; R² represents H or a hydrolysable ester, phosphate or carbamate group;

X represents halo; and n represents 1 , 2 or 3; or a pharmaceutically acceptable salt thereof.

In one aspect, the invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof, wherein each R¹ independently represents F, CF₃ or OCF₃. In one aspect, the invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof, wherein n represents 1 or 2.

In one aspect, the invention provides a compound of Formula Ia:

Ia wherein:

R^1a represents H or F; R^1b represents CF₃ or OCF₃;

R² represents H or a hydrolysable ester, phosphate or carbamate group; and X represents halo; or a pharmaceutically acceptable salt thereof.

In one aspect the invention provides a compound of Formula Ia or a salt thereof, wherein either R^1a is F and R^1b is CF₃ or R^1a is H and R^1b is OCF₃.

In one aspect the invention provides a compound of Formulae I or Ia or a salt thereof, wherein X represents F, Br or Cl, for example, Br or Cl. In a further aspect of the invention, X is Cl.

In one aspect the invention provides a compound of Formulae I or Ia or a salt thereof, wherein R² represents H. In a further aspect the invention provides a compound of Formulae I or Ia or a salt thereof, wherein R² represents a hydrolysable ester, phosphate or carbamate group, for example a hydrolysable phosphate group.

In one aspect, the invention provides a compound selected from: 5-chloro-2- (hydroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1 H)-one or a salt thereof and 5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2-(hydroxymethyl)-6- methyl-3,3'-bipyridin-4(1 H)-one or a salt thereof. In a further aspect, the invention provides 5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2-(hydroxymethyl)-6-methyl-3,3'-bipyridin- 4(1 H)-one or a salt thereof.

In one aspect, the invention provides a compound selected from: {5-chloro-6-methyl-4- oxo-6'-{4-[(trifluoromethyl)oxy]phenyl}-1 ,4-dihydro-3,3'-bipyridin-2-yl}methyl dihydrogen phosphate or a salt thereof and {5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-6-methyl-4- oxo-1 ,4-dihydro-3,3'-bipyridin-2-yl}methyl dihydrogen phosphate or a salt thereof. In a further aspect, the invention provides {(1H)-5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-

2-(hydroxymethyl)-6-methyl-4-oxo-3,3'-bipyridinyl} methyl dihydrogen phosphate or a salt thereof. Terms and Definitions

As used herein, "halo" refers to a fluoro, chloro, bromo or iodo group.

As used herein, the term "hydrolysable ester, phosphate or carbamate group", refers to any pharmaceutically acceptable ester, phosphate or carbamate that is hydrolysable under in vivo conditions in the human body. A compound of Formula I or a pharmaceutically acceptable salt thereof, wherein R² represents a hydrolysable ester, phosphate or carbamate group, is advantageously a prodrug of either: (a) a compound of Formula I wherein R² represents H or a pharmaceutically acceptable salt thereof; or (b) an active metabolite or residue of a compound of Formula I. Upon administration to the recipient said prodrug is advantageously capable of providing (directly or indirectly) either: (a) a compound of Formula I where R² is H or a pharmaceutically acceptable salt thereof; or (b) an active metabolite or residue of a compound of Formula I. Such derivatives are recognizable to those skilled in the art, without undue experimentation. Nevertheless, reference is made to the teaching of Burger's Medicinal Chemistry and Drug Discovery, 5th Edition, VoI 1 : Principles and Practice, which is incorporated herein by reference to the extent of teaching such derivatives.

Suitable pharmaceutically acceptable in vivo hydrolysable ester, phosphate or carbamate groups include those which break down readily in the human body to leave the parent acid or the salt thereof. An ester, phosphate or carbamate may be formed at a hydroxyl group (-OH) of a compound of Formula I using methods well known in the art involving reaction with the corresponding acid. Esters may, for example, be

esters, wherein alkyl is as defined herein, e.g. methyl esters, ethyl esters and the like. In one aspect of the invention, R² represents C(O)C_1-6alkyl. Carbamates may, for example, be carbamates of the formula -O(CO)N(Ci_-4alkyl)-Ci_-2alkyl-NH(Ci_-6alkyl). In one aspect of the invention, R² represents O(CO)N(Ci_-4alkyl)-Ci_-2alkyl-NH(Ci_-6alkyl. Phosphates may, for example, be phosphates of the formula -P(O)(OR)₂ , wherein each group R is independently selected from H or C_halky!. In one aspect of the invention, R² represents and P(O)(OR)₂ , wherein each R is independently selected from H or Ci_-6alkyl, for example P(O)(OH)₂. In some embodiments, a compound of Formula I, wherein R² represents a hydrolysable ester, phosphate or carbamate group, and in particular a phosphate group, may have an increased polarity compared to a compound Formula I, wherein R² represents H. Accordingly, in some embodiments the invention provides a compound of Formula I, wherein R² represents a hydrolysable ester, phosphate or carbamate group, and in particular a phosphate group, or a pharmaceutically acceptable salt thereof that is particularly suited for administration parenterally, for example, by injection or infusion.

It will be appreciated that certain salts of the compound according to Formula I may be prepared, since the compounds of the invention are weakly amphoteric. Indeed, in certain embodiments of the invention, salts of the compounds according to Formula I may be preferred over the respective free base or free acid because such salts impart greater stability or solubility to the molecule thereby facilitating formulation into a dosage form. Preferred salts are pharmaceutically acceptable salts. The compounds of the present invention may also be administered as a pharmaceutically acceptable salt. Accordingly, the invention is further directed to pharmaceutically acceptable salts of the compounds according to Formula I.

As used herein, the term "pharmaceutically acceptable salts" refers to salts that retain the desired biological activity of the subject compound and exhibit minimal undesired toxicological effects. For a review on suitable salts see Berge et al, J. Pharm. ScL, 1977, 66, 1-19. The term "pharmaceutically acceptable salts" includes both pharmaceutically acceptable acid addition salts and pharmaceutically acceptable base addition salts. These pharmaceutically acceptable salts may be prepared in situ during the final isolation and purification of the compound, or by separately reacting the purified compound in its free acid or free base form with a suitable base or acid, respectively. The salt may precipitate from solution and be collected by filtration or may be recovered by evaporation of the solvent.

Embodiments of compounds according to Formula I that contain an acidic functional group may be capable of forming pharmaceutically acceptable base addition salts by treatment with a suitable base. A pharmaceutically acceptable base addition salt may be formed by reaction of a compound of Formula I with a suitable inorganic or organic base (e.g. ammonia, triethylamine, ethanolamine, triethanolamine, tromethamine, choline, arginine, lysine or histidine), optionally in a suitable solvent such as an organic solvent, to give the base addition salt which is usually isolated for example by crystallisation and filtration. Pharmaceutically acceptable base salts include ammonium salts and salts with organic bases, including salts of primary, secondary and tertiary amines, including aliphatic amines, aromatic amines, aliphatic diamines, and hydroxy alkylamines, such as methylamine, ethylamine, isopropylamine, diethylamine, ethylenediamine, ethanolamine, trimethylamine, dicyclohexyl amine, diethanolamine, cyclohexylamine and N-methyl-D- glucamine. Other suitable pharmaceutically acceptable base salts include pharmaceutically acceptable metal salts, for example pharmaceutically acceptable alkali- metal or alkaline-earth-metal salts such as hydroxides, carbonates and bicarbonates of sodium, potassium, lithium, calcium, magnesium, aluminium, and zinc; in particular pharmaceutically acceptable metal salts of one or more carboxylic acid moieties that may be present in the compound of Formula I. For example, pharmaceutically acceptable salts of the compound of Formula (I) when R² is a phosphate ester of the formula P(O)(OH)₂, may include the base addition salt where R² is a derivatised as a -PO₃Na₂ group.

Embodiments of compounds according to Formula I that contain a basic functional group may be capable of forming pharmaceutically acceptable acid addition salts by treatment with a suitable acid. A pharmaceutically acceptable acid addition salt may be formed by reaction of a compound of Formula I or a prodrug thereof with a suitable strong inorganic or organic acid (such as hydrobromic, hydrochloric, hydroiodic, sulfuric, nitric, phosphoric, perchloric, p-toluenesulfonic, benzenesulfonic, methanesulfonic, ethanesulfonic, 2- hydroxyethanesulfonic, naphthalenesulfonic (e.g. 2-naphthalenesulfonic), optionally in a suitable solvent such as an organic solvent, to give the salt which is usually isolated for example by crystallisation and filtration. Pharmaceutically acceptable acid addition salts include a hydrobromide, hydrochloride, hydroiodide, sulfate, bisulfate, nitrate, phosphate, perchlorate, p-toluenesulfonate, benzenesulfonate, methanesulfonate, ethanesulfonate, 2- hydroxyethanesulfonate or naphthalenesulfonate (e.g. 2-naphthalenesulfonate) salt. In one embodiment, a pharmaceutically acceptable acid addition salt of a compound of Formula I is a salt of a strong acid, for example a hydrobromide, hydrochloride, hydroiodide, sulfate, nitrate, perchlorate, phosphate p-toluenesulfonic, benzenesulfonic, methanesulfonic salt. For example, pharmaceutically acceptable salts of the compound of Formula (I) when R² is a carbamate of the formula -O(CO)N(Ci_-4alkyl)-Ci_-2alkyl-NH(Ci- ₆alkyl), may include an acid addition salt where R² is a derivatised as a -0(CO)N(C_1- ₄alkyl)-C_1-2alkyl-N⁺H₂(C_1-6alkyl) group.

The 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 "compounds of the invention" means both the compounds according to Formula I and the salts, for example, pharmaceutically acceptable salts, thereof. The term "a compound of the invention" also appears herein and refers to both a compound according to Formula I and its salts.

The compounds of the invention may exist as solids or liquids, both of which are included in the invention. In the solid state, the compounds of the invention may exist as either amorphous material or in crystalline form, or as a mixture thereof. It will be appreciated that pharmaceutically acceptable solvates of compounds of the invention may be formed wherein solvent molecules are incorporated into the crystalline lattice during crystallisation. Solvates may involve non-aqueous solvents such as ethanol, isopropanol, dimethylsulfoxide (DMSO), acetic acid, ethanolamine, and ethyl acetate, or they may involve water as the solvent that is incorporated into the crystalline lattice. Solvates wherein water is the solvent that is incorporated into the crystalline lattice are typically referred to as "hydrates." The invention includes all such solvates and terms such as "compounds of the invention" and "compounds according to Formula I and pharmaceutically acceptable salts thereof" are to be understood as encompassing compounds and salts in both their solvated and non-solvated forms.

It will be appreciated that compounds of the invention can exist in different tautomeric forms. In particular, compounds of Formula I may exist in the 4-pyridinol tautomeric form as follows:

All possible tautomeric forms of the compounds of Formula I are contemplated to be within the scope of the present invention. In one aspect of the invention there is provided compounds of Formula I in the 4-pyridone tautomeric form.

It will also be appreciated that compounds of the invention which exist as polymorphs are contemplated to be within the scope of the present invention.

Properties and Uses of Compounds of the Invention The compounds of the invention show advantageous properties. In particular, the compounds of the invention have been shown to have good activity against parasitic target enzymes accompanied by low activity against human target enzymes, that is, they have been shown to be selective for parasitic target enzymes. They have also been shown to be more potent against parasitic target cells than against human cells, that is, they have shown selectivity for parasitic cells.

The compounds of the invention can be useful in the treatment of certain parasitic infections such as parasitic protozoal infections by the malarial parasite Plasmodium falciparum, species of Eimeria, Pneumocytis carnii, Trypanosoma cruzi, Trypanosoma brucei and Leishmania donovani. In particular, the compounds of the invention can be useful for treatment of infection by Plasmodium falciparum. Accordingly, the invention is directed to methods of treating such conditions and compounds for use in the chemotherapy of such conditions.

In one aspect, the invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof for use in medical therapy, including human or veterinary medical therapy. In a further aspect, the invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof for use in chemotherapy. In a further aspect, the invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof for use in the treatment of parasitic protozoal infections such as malaria, especially malaria caused by infection with Plasmodium falciparum. In a further aspect, the invention provides the use of a compound of Formula I or a pharmaceutically acceptable salt thereof in the manufacture of a medicament for the treatment of malaria. In another aspect, the invention provides a method for the treatment of a human or animal subject suffering from malaria, for example, malaria caused by infection with Plasmodium falciparum, comprising administering to said human or animal subject an effective amount of at least one a compound of Formula I or a pharmaceutically acceptable salt thereof. In one aspect, the invention provides a pharmaceutical composition comprising a compound of Formula I or a pharmaceutically acceptable salt thereof in admixture with one or more pharmaceutically acceptable carrier and/or excipient.

In a one aspect, the invention provides a pharmaceutical composition comprising a combination of a compound of Formula I or a pharmaceutically acceptable salt thereof and a further active therapeutic agent, such as another antiparasitic drug for example, a drug useful in the treatment of parasitic protozoal infections Such other active therapeutic agents include antimalarial drugs, such as folates (e.g. chloroquine, mefloquine, primaquine pyrimethamine, quinine, artemisinin, halofantrine, doxycycline, amodiquine, atovaquone, tafenoquine) and antifolates (e.g. dapsone, proguanil, sulfadoxine, pyrimethamine, chlorcycloguanil, cycloguanil).

The combinations referred to above may conveniently be presented for use in the form of a pharmaceutical formulation and thus pharmaceutical formulations comprising a combination as defined above together with a pharmaceutically acceptable carrier and/or excipient comprise a further aspect of the invention. The individual components of such combinations may be administered either sequentially or simultaneously in separate or combined pharmaceutical formulations by any convenient route.

When administration is sequential, either the compound of the present invention or the one or more additional active therapeutic agent(s) may be administered first. When administration is simultaneous, the combination may be administered either in the same or different pharmaceutical composition. When combined in the same formulation it will be appreciated that the compound of the present invention and the one or more additional active therapeutic agent(s) must be stable and compatible with each other and the other components of the formulation. When formulated separately the compound of the present invention and the one or more additional active therapeutic agent(s) may be provided in any convenient formulation, conveniently in such manner as are known for such compounds in the art.

As used herein, "treatment" means: (1 ) the amelioration or prevention of the condition being treated or one or more of the biological manifestations of the condition being treated, (2) the interference with (a) one or more points in the biological cascade that leads to or is responsible for the condition being treated or (b) one or more of the biological manifestations of the condition being treated, or (3) the alleviation of one or more of the symptoms or effects associated with the condition being treated. The skilled artisan will appreciate that "prevention" is not an absolute term. In medicine, "prevention" is understood to refer to the prophylactic administration of a drug to substantially diminish the likelihood or severity of a condition or biological manifestation thereof, or to delay the onset of such condition or biological manifestation thereof. In one aspect of the invention, "treatment" means the amelioration of the condition being treated or one or more of the biological manifestations of the condition being treated.

As used herein, "safe and effective amount" means an amount of the compound sufficient to significantly induce a positive modification in the condition to be treated but low enough to avoid serious side effects (at a reasonable benefit/risk ratio) within the scope of sound medical judgment. A safe and effective amount of a compound of the invention will vary with the particular compound chosen (e.g. depending on the potency, efficacy, and half- life of the compound); the route of administration chosen; the nature of the infection and/or condition being treated; the severity of the infection and/or condition being treated; the age, size, weight, and physical condition of the patient being treated; the medical history of the patient to be treated; the duration of the treatment; the nature of concurrent therapy; the desired therapeutic effect; and like factors, but can nevertheless be routinely determined by the skilled artisan.

As used herein, "patient" refers to a human or other animal.

The compounds of the invention may be administered by any suitable route of administration, including systemic administration. Systemic administration includes oral administration, parenteral administration, transdermal administration, rectal administration, and administration by inhalation. Parenteral administration refers to routes of administration other than enteral, transdermal, or by inhalation, and is typically by injection or infusion. Parenteral administration includes intravenous, intramuscular, and subcutaneous injection or infusion. Inhalation refers to administration into the patient's lungs whether inhaled through the mouth or through the nasal passages. Topical administration includes dermal application to the skin as well as intraocular, buccal (e.g. sub-lingually), rectal, intravaginal, and intranasal administration.

Suitable dosing regimens for a compound of the invention depend on the pharmacokinetic properties of that compound, such as absorption, distribution, and half-life, which can be determined by the skilled artisan. In addition, suitable dosing regimens for a compound of the invention, including the duration such regimens are administered, depend on the route of administration of the compound, on the condition being treated, the severity of the condition being treated, the age and physical condition of the patient being treated, the medical history of the patient to be treated, the nature of any concurrent therapy, the desired therapeutic effect, and like factors within the knowledge and expertise of the skilled artisan. It will be further understood by such skilled artisans that suitable dosing regimens may require adjustment given an individual patient's response to the dosing regimen or over time as individual patient needs change. It will also be appreciated that if the compounds of the present invention are administered in combination with one or more additional active therapeutic agents as discussed further hereinbelow, the dosing regimen of the compounds of the invention may also vary according to the nature and amount of the one or more additional active therapeutic agents as necessary. Typical daily dosages may vary depending upon the particular route of administration chosen. Typical daily dosages for oral administration range from about 0.01 to about 25 mg/kg, in one embodiment from about 0.1 to about 14 mg/kg. Typical daily dosages for parenteral administration range from about 0.001 to about 10 mg/kg; in one embodiment from about 0.01 to about 6 mg/kg.

Compositions

The compounds of the invention will normally, but not necessarily, be formulated into pharmaceutical compositions prior to administration to a patient. In one aspect, the invention is directed to pharmaceutical compositions comprising a compound of the invention. In another aspect the invention is directed to pharmaceutical compositions comprising a compound of the invention and a pharmaceutically acceptable carrier and/or excipient. The carrier and/or excipient must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

The pharmaceutical compositions of the invention may be prepared and packaged in bulk form wherein a safe and effective amount of a compound of the invention can be extracted and then given to the patient such as with powders or syrups. Alternatively, the pharmaceutical compositions of the invention may be prepared and packaged in unit dosage form wherein each physically discrete unit contains a safe and effective amount of a compound of the invention. When prepared in unit dosage form, the pharmaceutical compositions of the invention typically contain from about 0.1 to 100 mg, in another aspect 0.1 mg to about 50 mg of a compound of the invention.

The pharmaceutical compositions of the invention typically contain one compound of the invention. However, in certain embodiments, the pharmaceutical compositions of the invention contain more than one compound of the invention. For example, in certain embodiments the pharmaceutical compositions of the invention contain two compounds of the invention. In addition, the pharmaceutical compositions of the invention may optionally further comprise one or more additional active therapeutic compounds. The pharmaceutical compositions of the invention typically contain more than one pharmaceutically acceptable excipient. However, in certain embodiments, the pharmaceutical compositions of the invention contain one pharmaceutically acceptable excipient.

As used herein, the term "pharmaceutically acceptable" means suitable for pharmaceutical use.

The compound of the invention and the pharmaceutically acceptable excipient or excipients will typically be formulated into a dosage form adapted for administration to the patient by the desired route of administration. For example, dosage forms include those adapted for (1 ) oral administration such as tablets, capsules, caplets, pills, troches, powders, syrups, elixirs, suspensions, solutions, emulsions, sachets, and cachets; (2) parenteral administration such as sterile solutions, suspensions, and powders for reconstitution; and (3) rectal administration such as suppositories.

Suitable pharmaceutically acceptable excipients will vary depending upon the particular dosage form chosen. In addition, suitable pharmaceutically acceptable excipients may be chosen for a particular function that they may serve in the composition. For example, certain pharmaceutically acceptable excipients may be chosen for their ability to facilitate the production of uniform dosage forms. Certain pharmaceutically acceptable excipients may be chosen for their ability to facilitate the production of stable dosage forms. Certain pharmaceutically acceptable excipients may be chosen for their ability to facilitate the carriage or transport of the compound or compounds of the invention from one organ, or portion of the body, to another organ, or portion of the body, once administered to the patient. Certain pharmaceutically acceptable excipients may be chosen for their ability to enhance patient compliance.

Suitable pharmaceutically acceptable excipients include the following types of excipients: binders, disintegrants, lubricants, glidants, granulating agents, coating agents, wetting agents, solvents, co-solvents, suspending agents, emulsifiers, sweeteners, flavouring agents, flavour masking agents, colouring agents, anti-caking agents, humectants, chelating agents, plasticizers, viscosity increasing agents, antioxidants, preservatives, stabilizers, surfactants, and buffering agents. The skilled artisan will appreciate that certain pharmaceutically acceptable excipients may serve more than one function and may serve alternative functions depending on how much of the excipient is present in the formulation and what other ingredients are present in the formulation. Skilled artisans possess the knowledge and skill in the art to enable them to select suitable pharmaceutically acceptable excipients in appropriate amounts for use in the invention. In addition, there are a number of resources that are available to the skilled artisan which describe pharmaceutically acceptable excipients and may be useful in selecting suitable pharmaceutically 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).

The pharmaceutical compositions of the 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).

In one aspect, the invention is directed to a solid or liquid oral dosage form such as a liquid, tablet, lozenge or a capsule, comprising a safe and effective amount of a compound of the invention and a carrier. The carrier may be in the form of a diluent or filler. Suitable diluents and fillers in general include lactose, sucrose, dextrose, mannitol, sorbitol, starch (e.g. corn starch, potato starch, and pre-gelatinized starch), cellulose and its derivatives (e.g. microcrystalline cellulose), calcium sulfate, and dibasic calcium phosphate. A liquid dosage form will generally consist of a suspension or solution of the compound or salt in a liquid carrier for example, ethanol, olive oil, glycerine, glucose (syrup) or water (e.g. with an added flavouring, suspending, or colouring agent). Where the composition is in the form of a tablet or lozenge, any pharmaceutical carrier routinely used for preparing solid formulations may be used. Examples of such carriers include magnesium stearate, terra alba, talc, gelatin, acacia, stearic acid, starch, lactose and sucrose. Where the composition is in the form of a capsule, any routine encapsulation is suitable, for example using the aforementioned carriers or a semi solid e.g. mono di- glycerides of capric acid, Gelucire™ and Labrasol™, or a hard capsule shell e.g. gelatin. Where the composition is in the form of a soft shell capsule e.g. gelatin, any pharmaceutical carrier routinely used for preparing dispersions or suspensions may be considered, for example aqueous gums or oils, and may be incorporated in a soft capsule shell.

An 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, and pre-gelatinized starch), gelatin, acacia, sodium alginate, alginic acid, tragacanth, guar gum, povidone, and 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 carboxymethyl cellulose. The oral solid dosage form may further comprise an excipient in the form of a lubricant. Suitable lubricants include stearic acid, magnesium stearate, calcium stearate, and talc.

There is further provided by the present invention a process of preparing a pharmaceutical composition, which process comprises mixing at least one compound of Formula I or a pharmaceutically acceptable derivative thereof, together with a pharmaceutically acceptable carrier and/or excipient.

Preparations for oral administration may be suitably formulated to give controlled/extended release of the active compound.

All publications, including but not limited to patents and patent applications cited in this specification are herein incorporated by reference as if each individual publication were specifically and individually indicated to be incorporated by reference as though fully set forth. Abbreviations

In describing the invention, chemical elements are identified in accordance with the Periodic Table of the Elements. Abbreviations and symbols utilized herein are in accordance with the common usage of such abbreviations and symbols by those skilled in the chemical arts. The following abbreviations are used herein:

ACN acetonitrile

AcOEt ethyl acetate anh. anhydrous approx. approximately brine saturated aqueous sodium chloride

CDCI₃ deuterated chloroform

CD₃OD deuterated methanol

DCM dichloromethane DMSO dimethylsulfoxide

DMSO-de deuterated dimethylsulfoxide

DMF N,N-dimethylformamide

EtOH ethanol h hour(s) Hex hexane

HPLC High Performance Liquid Chromatography iPr₂NH diisopropylamine max. maximum

MeOH methanol MgSO₄ magnesium sulfate

NaTaurochol. sodium Taurocholic

NaHCO₃ sodium bicarbonate

Na₂SO₄ sodium sulfate

NBS N-bromosuccinimide n-BuLi or BuLi n-butyllithium

NCS N-chlorosuccinimide

Pd(C) palladium on activated carbon r.t. room temperature sat. saturated TBDMS te/f-butyldimethylsilane tBuOMe te/f-butyl methyl ether

TCCA trichloroisocyanuric acid

THF tetrahydrofuran

ToI toluene (methylbenzene) NMR Nuclear Magnetic Resonance spectroscopy

ES MS Electrospray mass spectrometry Compound Preparation

The general procedures used to synthesise the compounds of Formula I are described in reaction Schemes 1-7 and are illustrated in the Examples.

Throughout the specification, general Formulae are designated by Roman numerals I, II, III, IV etc. Subsets of compounds of Formula I are defined as Ia, Ib and Ic; subsets of other Formulae are expressed in an analogous fashion.

Compounds of Formula Ib, which are compounds of Formula I in which R² is H, may be prepared from compounds of Formula Il wherein n and each R¹ are as defined for Formula I, according to Scheme 1. Compounds of Formula Il may be reacted with an appropriate halogenating agent. The halogenating agent is for example a halosuccinimide (NBS, NCS), trichloroisocyanuric acid (TCCA) or bromine. A suitable solvent is for example a mixture of dichloromethane and methanol.

Scheme 1

Compounds of Formula Il may be prepared from compounds of Formula III, wherein n and each R¹ are as defined for Formula I, according to Scheme 2 by treatment of the compound of Formula III with aqueous ammonia in a suitable solvent such as ethanol or methanol, suitably with heating under pressure, optionally in the presence of microwave radiation. In one aspect, the reaction is carried out in a steel reactor at elevated temperature for a period of between 1 h and 8h. In another aspect the reaction is carried out at elevated temperature and optionally elevated pressure in a microwave oven, e.g. for a period of 30 - 150 minutes.

Scheme 2

Compounds of Formula III, may be prepared by the coupling reaction between

compounds of Formula IVa, wherein, R' = , i.e. OR' is bis(pinacol), and wherein n and each R¹ are as defined for Formula I above, and compound of the Formula V according to Scheme 3. The reaction is carried out in a suitable solvent and suitable conditions, such as dry DMF at an elevated temperature such as 80 ⁰C, in the presence of a suitable palladium (II) catalyst such as [1 ,1'-bis(diphenylphosphino)ferrocene]dichloro- palladium(ll) or bis(triphenylphosphine)palladium(ll) chloride and a base such as potassium carbonate.

Compounds of Formula III may alternatively be prepared by the coupling reaction between compounds of Formula IVb, wherein R' is H and wherein n and each R¹ are as defined for Formula I above, and 2-({[(1 ,1-dimethylethyl)(dimethyl)silyl]oxy}methyl)-6-methyl-4-oxo- 4H-pyran-3-yl trifluoromethanesulfonate (prepared according to the procedure described in WO2007/138048, Intermediate 6) according to Scheme 3. The reaction is carried out in a suitable solvent and suitable conditions, such as a mixture of dry ethanol and dry toluene at an elevated temperature, e.g. 50 ⁰C to 12O ⁰C, in the presence of a suitable palladium catalyst such as bis(triphenylphosphine)palladium(ll) chloride and a base, such as sodium carbonate.

palladiumcatalyst, base

IVb: R' = H

Scheme 3

Boronic acid compounds of Formula IVa may be obtained from compounds of Formula V wherein n and each R¹ is as defined for Formula I above, according to Scheme 4. A compound of Formula V may be coupled with bis(pinacolato)diboron in the presence of a suitable palladium catalyst such as [1 ,1'-bis(diphenylphosphino)ferrocene]dichloro- palladium(ll) or bis(triphenylphosphine)palladium(ll) chloride in the presence of potassium acetate and 1 ,1 ^'-bis(diphenylphosphino)ferrocene or bis(triphenylphosphine)palladium(ll) chloride a suitable solvent, such as anhydrous dioxane at an elevated temperature, e.g.

50 ⁰C to 100 ⁰C to afford a compound of Formula IVa.

Scheme 4 Boronic acid compounds of Formula IVb may be obtained from compounds of Formula V wherein n and each R¹ is as defined for Formula I above, according to Scheme 5. Compounds of Formula V may be treated with an alkyl borate such as triisopropyl borate in the presence of a strong base such as butyllithium at a temperature between -30 ⁰C and -78 ⁰C, for example -4O⁰C in the presence of an alkyl borate, such as tri- isopropylborate, in a suitable solvent, such as THF to afford compound of the Formula IVb following an acidic workup.

1. Base, low temperature

2. alkyl borate

3. acidic workup

Scheme 5

Compounds of Formula V may be prepared from the Suzuki coupling reaction between boronic acid compounds of Formula VII, which are commercially available and/or readily prepared using standard techniques, and 2,5-dibromopyridine compound Vl, which is commercially available, according to Scheme 6. The compound of Formula Vl may be heated with VII in the presence of a suitable base, such as sodium carbonate or caesium carbonate, and a suitable palladium catalyst such as bis(triphenylphosphine)palladium(ll) chloride or tetrakis(triphenylphosphine)palladium (0), in an appropriate solvent such as a mixture of toluene and ethanol or acetonitrile at a suitable temperature, e.g. 50 ⁰C to 120 ⁰C.

Scheme 6

Compounds of the Formula Ic, which are compounds of Formula I in which R² is a phosphate ester and wherein n and each R¹ are as defined for Formula I, may be prepared from compounds of Formula Ib, according to Scheme 7. The compound of Formula Ib may be deprotonated with a metal hydride such as lithium hydride in the presence of a hindered alcohol, such as te/f-butyl alcohol, in a suitable solvent, such as anhydrous tetrahydrofuran, and then reacted with tetrabenzyl pyrophosphate at a low temperature, e.g. -20 to 5 ⁰C, to afford an intermediate of the Formula VII. The benzyl protecting groups can be removed from the phosphate group of the compound of Formula VII using hydrogenation, for example using palladium on activated charcoal and a hydrogen source, such as hydrogen gas, 1 ,4-cyclohexadiene or formic acid, in a suitable solvent, such as a mixture of methanol and dichloromethane, to provide the phosphate ester of Formula Ic as a free acid.

Scheme 7

Base addition compounds of Formula I may be prepared from treatment of the compounds with a base in a suitable solvent under standard conditions. For example, to make the sodium salts of compounds of Formulae Ib or Ic, the compounds may be treated with sodium hydroxide in a suitable solvent such as methanol or water, or a mixture thereof.

Those skilled in the art will appreciate that in the preparation of the compound of Formula I or a pharmaceutically acceptable salt thereof, it may be necessary and/or desirable to protect one or more sensitive groups in the molecule or the appropriate intermediate to prevent undesirable side reactions. Suitable protecting groups for use according to the present invention are well known to those skilled in the art and may be used in a conventional manner. See, for example, "Protective groups in organic synthesis" by T.W. Greene and P. G. M. Wuts (John Wiley & sons 1991 ) or "Protecting Groups" by PJ. Kocienski (Georg Thieme Verlag 1994). Examples of suitable oxygen protecting groups may include for example alky silyl groups, such as trimethylsilyl or te/t-butyldimethylsilyl; alkyl ethers such as tetrahydropyranyl or te/t-butyl; or esters such as acetate.

EXPERIMENTAL SECTION

Examples

The examples provided in the following Experimental Section illustrate the invention. These examples are not intended to limit the scope of the invention, but rather to provide guidance to the skilled artisan to prepare and use the compounds, compositions, and methods of the invention. While particular embodiments of the invention are described, the skilled artisan will appreciate that various changes and modifications can be made without departing from the spirit and scope of the invention.

The compounds of Examples 1 and 2 of the invention were prepared as summarised in Scheme 8 below:

Intermediate 1 : n=1 ; R= 4-OCF₃ Intermediate 2: n=2; R= 2-F, 4-CF₃

Intermediate 13: n=1 ; R=4-OCF₃ Intermediate 5: n=1 ; R=4-OCF₃ Intermediate 6: n=2; R=2-F, 4-CF₃ Intermediate 3: n=2; R=2-F, 4-CF₃ (R^'= H) Intermediate 4: n=2; R=2-F, 4-CF₃

Example 1 : n=1 ; R=4-OCF₃

Intermediate 7: n=1 ; R=4-OCF₃ Example 2: n=2; R=2-F, 4-CF₃ Intermediate 8: n=1 ; R=2-F, 4-CF₃

Scheme 8

The compounds of Examples 1 and 2 were also prepared using an alternative process from (4-iodo-5-methyl-3-isoxazolyl)methanol as summarised in Scheme 9 below:

Intermediate 13: n=1 ; R=4-OCF3 4-CF₃

WO2007/138048 Intermediate 9: n=1 ; R=4-OCF₃ Intermediate 22 Intermediate 11 : n=2; R=2-F, 4-CF₃

Example 1 n=1 ; R=4-OCF₃ Intermediate 10: n=1 ; R=4-OCF₃ Example 2: n=2; R=2-F, 4-CF₃ Intermediate 12: n=2; R=2-F, 4-CF₃

Intermediate 15: n=1 ; R=4-OCF3 Example 4: n=1 ; R=4-OCF3 Intermediate 14: n=2; R=2-F, 4-CF3 Example 3: n=2; R=2-F, 4-CF3

Scheme 9

Intermediate 1

5-bromo-2-{4-r(trifluoromethyl)oxylphenyl)pyridine

A mixture of 5.00 g (21.11 mmol) of 2,5-dibromopyridine (ALDRICH), 7.56 g (23.22 mmolo) of caesium carbonate and 4.13 g (20.05 mmol) of 4- (trifluoromethoxy)benzeneboronic acid (FRONTIER SCIENTIFIC) in 165 ml Tol/EtOH (10:1 ) was stirred and bubbled with argon for 15 min. To this mixture were added 0.741 g (1.055 mmol) of bis(triphenylphosphine)palladium(ll) chloride, it was bubbled with argon for another 15 min. The reaction was heated 1 h at 80 ⁰C. The reaction mixture was quenched with water and extracted with AcOEt. Combined the organic layers were washed with saturated brine, dried over sodium sulfate and evaporated in vacuo. The residue obtained was purified by flash master (20 g, Sill, 15:1 Hex:AcOEt) to afford 5.8 g of the title compound.

¹H NMR (δ, ppm, DMSO-d₆ ): 8.80 (d, 1 H); 8.25-8.10 (m, 3H); 7.99 (d, 1 H); 7.48 (d, 2H). [ES MS] m/z: 318 [M+H]⁺.

Intermediate 2 5-bromo-2-r2-fluoro-4-(trifluoromethyl)phenyllpyridine

To a stirred mixture under nitrogen of 3.76 g (15.8 mmol) of 2,5-dibromopyridine, 3 g (14.4 mmol) of [2-fluoro-4-(trifluoromethyl)phenyl]boronic acid (FLUOROCHEM) and 21.6 ml of sodium carbonate 2M (43.3 mmol) in 108 ml of toluene and 36 ml of ethanol (3 : 1 ), 0.83 g (0.7 mmol) of tetrakis(triphenylphosphine)palladium (0) were added. The mixture was allowed to react at 80 ° C overnight. Then, the suspension was diluted with 100 ml of AcOEt and washed with water (3 x 50 ml). The organic phase was dried with MgSO₄ anh. and the solvent evaporated affording 4.1g of crude material which contained approximately 10% of 2-bromo-5-[2-fluoro-4-(trifluoromethyl)phenyl]pyridine. The resulting crude was used without any further purification.

¹H NMR (δ, ppm, DMSO-d₆ ) 8.89 (d, 1 H); 8.22 (ddd, 1 H); 8.13 (t, 1 H); 7.8-7.7 (m, 2 H); 7.73 (m, 1 H).

Intermediate 3

{6-[2-fluoro-4-(trifluoromethyl)phenyl1-3-pyridinyl)boronic acid

Method A: To a solution of 2.66 g (8.31 mmol) of 5-bromo-2-[2-fluoro-4- (trifluoromethyl)phenyl]pyridine (Intermediate 2) in a mixture of 16 ml of toluene and 4 ml of tetrahydrofuran stirred under nitrogen at r.t, were added 2.3 ml (9.97 ml) of triisopropyl borate. The mixture was cooled down to -40 ⁰C and 3.99 ml of butyllithium (2.5 M in hexane, 9.97 mmol)) was added dropwise for 30 minutes. Once the addition was finished, the mixture was stirred at -40 ⁰C. After 30 minutes, remaining starting pyridine was observed so 0.66 ml of butyllithium (2.5 M in hexane, 1.6 mmol)) was added. After 15 minutes no more starting material was detected. The mixture was then allowed to warm up to -20 ⁰C before 3.8 ml of a 2N HCI solution was added. A solid appeared, pH of the aqueous phase was around 7. The mixture was allowed to reach room temperature. The solid was filtered and dried under vacuum yielding 233 mg of solid which was consistent with the desired product but not pure. The filtrate was transferred to a separating funnel where the two phases were separated. The aqueous phase was extracted with THF (3 x 15ml) and these extracts were collected together with the original organic phase and the solid obtained by filtration. The combined THF extracts were co-evaporated with dichloromethane in vacuo to provide 2.49 g of the titled compound as a yellow solid which was used without any further purification.

Method B:

Step 1

5-bromo-2-iodopyridine (5 g, 17.61 mmol)), 2-fluoro-4-(trifluoromethyl)phenylboronic acid (FLUOROCHEM) (4.76 g, 22.90 mmol) and bis(triphenylphosphine)palladium(ll) chloride (0.371 g, 0.528 mmol) were charged in a 500 ml. round bottom flask. It was purged with argon and ethanol (350 ml) was added. The mixture was stirred at room temperature for 20 min until all reagents were completely dissolved. Then, 2 M sodium carbonate (26.4 ml, 52.8 mmol) was added dropwise and the mixture was heated to 85 ⁰C. More 2-fluoro- 4-(trifluoromethyl)phenylboronic acid (0.2eq) was added and the mixture was stirred overnight at r.t., and then heated to 9O⁰C for 2h. Once the reaction was completed, it was allowed to cool to room temperature. Ethanol was removed under reduced pressure, the crude was dissolved in te/f-butyl methyl ether (200 ml.) and washed successively with 10% Na₂S₂O₅ (25OmL), 1 N NaOH (250 mL) and brine (15OmL). The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated to dryness. A minimal amount of cold MeOH was added and the mixture was stirred below O⁰C for 15min. The solid was carefully filtered to obtain desired product as a pale yellow solid (4.95 g). H-NMR (δ, ppm, CDCI₃): 8.80 (s, 1 H); 8.16 (t, 1 H); 7.94-7.92 (m, 1 H); 7.75 (d, 1 H); 7.55- 7.43 (m, 3H)

Step 2

To a solution of crude 5-bromo-2-[2-fluoro-4-(trifluoromethyl)phenyl]pyridine (made according to Step 1 ) (3.75 g, 1 1.72 mmol) in 1 ,4-dioxane (6OmL) and deoxygenated with argon, bis(pinacolato) diboron (ALDRICH) (3.57g, 14.06 mmol) and bis(triphenylphosphine)palladium(ii) chloride (0.164 g, 0.234 mmol) were added then potassium acetate (3.45 g, 35.1 mmol) was added. The mixture was heated to 100 ⁰C for approx 5 h. The mixture was allowed to cool to room temperature with stirring overnight, then, filtered through celite, and concentrated to dryness. The crude was suspended in a 120 ml of a mixture acetone/water v/v 1 :1 and ammonium acetate (2.0 g, 26.4 mmol) was added followed by NaIO₄ (5.6g, 26.4 mmol). The mixture was stirred at room temperature overnight. The organic solvent was evaporated under reduced pressure and 2N NaOH (30 ml.) was added. The mixture was stirred at room temperature for 15 min then extracted with CH₂CI₂ (2x 60 ml_). The aqueous layer was concentrated under reduced pressure (in order to eliminate traces of DCM) and filtered. The resulting solution was cooled to 0 ⁰C, and 2N HCI was added drop-wise until pH was adjusted to 5. The white solid precipitated was filtered and dried under vacuum. It was partitioned in DCM and 2N NaOH and layers were separated. Aqueous layer was back extracted with AcOEt. Aqueous basic solution was concentrated and filtered. 1 N HCI was then added dropwise at r.t until pH was adjusted to 7.5. The precipitated was filtered and dried over vacuum to get the title compound (1.2g).

H-NMR (δ, ppm, DMSO-d₆): 9.03 (s, 1 H); 8.26-8.15 (m, 2H); 7.85-7.82 (m, 2H); 7.74-7.71 (d, 1 H).

Intermediate 4

2-[2-fluoro-4-(trifluoromethyl)phenyl1-5-(4,4,5,5-tetramethyl-1 ,3,2-dioxaborolan-2- vDpyridine

A stirred solution of 3 g (9.3 mmol) of 5-bromo-2-[2-fluoro-4- (trifluoromethyl)phenyl]pyridine (Intermediate 2), 3.0 g of bis(pinacolato)diboron, 2.7 g (28.1 mmol) of potassium acetate, 206 mg (0.28 mmol) of [1 ,1'- bis(diphenylphosphino)ferrocene]dichloro-palladium(ll) and 161 mg (0.281 mmol) of 1 ,1 ^'- bis(diphenylphosphino)ferrocene (97%) in 54.2 ml of anhydrous dioxane was heated at 8O⁰C overnight. The mixture was diluted with 2 ml of AcOEt, filtered and washed with water (2 x 20 ml) and brine (2 x 20 ml). The organic phase was dried with MgSO₄ and evaporated. The residue was purified by flash chromatography affording 2.6 g of a white solid mixed with some starting material, so the product was re-purified affording 2.1 g of the desired product as a white solid.

A¹H NMR (δ, ppm, CDCI₃) 9.06 (s, 1 H); 8.2-8.1 (m, 2 H); 7.81 (dd, 1 H); 7.5 (d, 1 H); 7.4 (d, 1 H), 1.38 (s, 12 H).

Intermediate 5 2-({r(1 ,1-dimethylethyl)(dimethyl)silylloxy)methyl)-6-methyl-3-(6-{4- r(trifluoromethyl)oxylphenyl)-3-pyridinyl)-4H-pyran-4-one

Step 1

To a solution of 1.25 g (3.93 mmol) of 5-bromo-2-{4-[(trifluoromethyl)oxy]phenyl}pyridine (Intermediate 1 ) in a mixture of 8 ml of toluene and 4 ml of tetrahydrofuran stirred under nitrogen at room temp were added 1.088 ml of triisopropyl borate (4.72 mmol). The mixture was cooled to -40 ⁰C and 1.89 ml (4.72 mmol) of butyllithium 2.5 M in hexane were added dropwise over 30 minutes, the mixture was stirred at -40 ⁰C. After 30 min, the reaction mixture was allowed to warm to -20 ⁰C and 1.8 ml of 2N HCI solution were added, pH of the aqueous phase was around 7. Mixture was allowed to reach room temperature. The two phases were separated. The aqueous phase was extracted with THF, these extracts were collected together with the original organic phase. The combined extracts were co-evaporated with dichloromethane in vacuo to afford 1.65g (6-{4- [(trifluoromethyl)oxy]phenyl}-3-pyridinyl)boronic acid which was used in next step without purification.

Step 2

To a solution of 736 mg (2.60 mmol) of (6-{4-[(trifluoromethyl)oxy]phenyl}-3- pyridinyl)boronic acid (Intermediate 13) and 1.361 g (3.38 mmol) of 2-({[(1 ,1- dimethylethyl)(dimethyl)silyl]oxy}methyl)-6-methyl-4-oxo-4H-pyran-3-yl trifluoromethane- sulfonate (prepared according to the procedure described in WO 2007/138048, Intermediate 6) in 21 ml of anhydrous ethanol and 7ml of anhydrous toluene were stirred and bubbled with argon for 15 min. To this solution 1.103g (10.4 mmol) of sodium carbonate and 183 mg (0.260 mmol) of bis(triphenylphosphine)palladium(ll) chloride were added. The reaction mixture was bubbled with argon for additional 10 min, then heated to 80 ⁰C for 2h. Additional 450 mg (1.56 mmol) of (6-{4-[(trifluoromethyl)oxy]phenyl}-3- pyridinyl)boronic acid and an 183 mg (0.260 mmol) of bis(triphenylphosphine)palladium(ll) chloride were added. The reaction mixture was stirred for another 1 h at 8O⁰C. The reaction mixture was filtered through a glass fritted funnel and filtrate was evaporated in vacuo. The residue obtained was purified by flash master (70 g, BPSiO₂ cartridge, Hex:AcOEt 0-50%) to afford 850 mg of the title compound. 1H NMR (δ, ppm, CD₃OD): 8.58.8.51 (m, 1 H); 8.17-8.07 (m, 2H); 8.00-7.91 (m, 1 H); 7.88- 7.79 (m, 1 H); 7.45-7.35 (m, 2H); 6.38-6.32 (m, 1 H); 4.53-4.46 (m, 2H); 2.44-2.36 (m, 3H); 0.91-0.83 (m, 9H); 0.08-0.01 (m, 6H). [ES MS] m/z: 492 [M+H]⁺.

Intermediate 6 2-({r(1 ,1-dimethylethyl)(dimethyl)silylloxy)methyl)-3-{6-r2-fluoro-4-(trifluoromethyl)phenyll- 3-pyridinyl)-6-methyl-4/-/-pyran-4-one

Method A:

A solution of 2.2 g (5.47 mmol) of 2-({[(1 ,1-dimethylethyl)(dimethyl)silyl]oxy}methyl)-6- methyl-4-oxo-4H-pyran-3-yl trifluoromethanesulfonate (prepared according to the procedure described in WO 2007/138048, Intermediate 6) and 1.2 g (4.21 mmol) of {6-[2- fluoro-4-(trifluoromethyl)phenyl]-3-pyridinyl}boronic acid (Intermediate 3) in 21 ml of anhydrous ethanol and 7 ml of anhydrous toluene was stirred and bubbled with argon for 15 min. To this solution 1.8 g (16.84 mmol) of sodium carbonate and bis(triphenylphosphine)palladium(ll) chloride (296 mg, 0.421 mmol)) were added. The reaction mixture was bubbled with argon for additional 10 min, then heated to 80 ⁰C. After 2 h additional 0.6 g (2.11 mmol) of {6-[2-fluoro-4-(trifluoromethyl)phenyl]-3- pyridinyl}boronic acid and 69.5 mg (0.0099 mmol) of bis(triphenylphosphine)palladium(ll) chloride were added and the mixture was heated to 80 ⁰C for 1 h. The reaction mixture was filtered through a glass fritted funnel and salts were washed with toluene. The filtrate was evaporated under vacuum to dryness to give 3 g of brown oil. Salts were washed with ethanol and the filtrate was evaporated under vacuum to give 386 mg of an orange solid that was identified as the title compound. The brown oil was triturated with acetonitrile and filtered on a glass fritted funnel affording 500 mg of a cream solid which was further purified by chromatography (5Og BPSiO₂ cartridge, Hex:AxOEt o-40%) affording a second batch of the desired compound (327 mg) as an off-white solid.

¹H NMR (δ, ppm, CD₃OD) 8.58 (s, 1 H), 8.08 (t, 1 H), 7.9-7.8 (m, 2 H), 7.59 (m, 2 H), 6.31 (s, 1 H), 4.46 (s, 2 H), 2.36 (s, 3 H), 0.87 (s, 9 H), 0.05 (s, 6 H). [ES MS] m/z: 494 [M+H]⁺.

Method B: To a stirred solution under nitrogen atmosphere of 1.5g (3.73 mmol) of 2-({[(1 ,1- dimethylethyl)(dimethyl)silyl]oxy}methyl)-6-methyl-4-oxo-4H-pyran-3-yl trifluoromethanesulfonate (prepared according to the procedure described in WO 2007/138048, Intermediate 6), 1.36 g (3.73 mmol) of 2-[2-fluoro-4-

(trifluoromethyl)phenyl]-5-(4,4,5,5-tetramethyl-1 ,3,2-dioxaborolan-2-yl)pyridine (Intermediate 4) and 1.5 g (11.18 mmol) of potassium carbonate in 12.4 ml of DMF, 136 mg (0.18 mmol) of [1 ,1'-Bis(diphenylphosphino)ferrocene]dichloro-palladium(ll) were added. The mixture was heated at 80 ° C. After 2 h no starting material was detected. The mixture was diluted with 12.4 ml AcOEt and filtered through a celite cartridge. The AcOEt of the filtrate was evaporated and the crude was dissolved in te/f-butyl methyl ether (20 ml_), and washed with NH₄CI sat. (2 x 10 ml_), NaOH (1 N) ( 2 x 5 ml_), HCI (1 N) (2 x 5 ml.) and NaCI sat. (10 ml_). The organic phase was dried with MgSO₄ anh. and the solvent evaporated. The crude was purified by flash chromatography affording 560 mg of the title compound.

¹H NMR (δ, ppm, CDCI₃) 8.67 (s, 1 H), 8.19 (t, 1 H), 7.9-7.7 (m, 2 H), 7.55 (d, 1 H), 7.45 (d, 1 H), 6.28 (s, 1 H), 4.44 (s, 2 H), 2.36 (s, 3 H), 0.89 (s, 9 H), 0.06 (s, 6 H).

Intermediate 7

2-(hvdroxymethyl)-6-methyl-6'-{4-r(trifluoromethyl)oxylphenyl)-3,3'-bipyridin-4(1 H)-one

In a 20 ml. vessel microwave 500 mg (1.017 mmol) of 2-({[(1 ,1- dimethylethyl)(dimethyl)silyl]oxy}methyl)-6-methyl-4-oxo-4H-pyran-3-yl trifluoromethanesulfonate (prepared according to the procedure described in WO 2007/138048, Intermediate 6) were dissolved in 8 ml of ethanol. 5.78 ml (85 mmol) of ammonia (32% in water) were added, the reaction vessel was sealed and heated in a Biotage Initiator device using very high absorption to 140 ⁰C for 50 min. After cooling, reaction was evaporated to dryness. The solid residue was triturated with diethyl ether, filtered and washed with diethyl ether, dried under vacuum to afford 355 mg of the title compound.

¹H NMR (δ, ppm, DMSOd₆ ): 8.48 (dd, 1 H); 8.21 (d, 2H); 7.93 (dd, 1 H); 7.72 (dd, 1 H); 7.46 (d, 2H); 5.97 (s, 1 H); 4.17 (s, 2H); 2.18 (s, 3H). [ES MS] m/z: 377 [M+H]⁺.

Intermediate 8

6'-r2-fluoro-4-(trifluoromethyl)phenyll-2-(hvdroxymethyl)-6-methyl-3,3'-bipyridin-4(1 /-/)-one

500 mg (1 mmol) of 2-({[(1 ,1-dimethylethyl)(dimethyl)silyl]oxy}methyl)-3-{6-[2-fluoro-4- (trifluoromethyl)phenyl]-3-pyridinyl}-6-methyl-4/-/-pyran-4-one (Intermediate 6) were dissolved in 5 ml of ethanol using a 20 ml-microwave vessel. Then, 6 ml of ammonia solution 32% were added. The vessel was sealed and heated during 2 h in a Biotage Initiator at 145 ⁰C, Pmax=16 bar, Afterwards, the solvent was evaporated affording 300 mg of an orange solid. ¹H NMR (δ, ppm, DMSO-d₆ ) 11.22 (s, NH); 8.58 (s, 1 H); 8.21 (t, 1 H); 7.8-7.7 (m, 4 H); 6.03 (s, 1 H); 5.61 (s, OH); 4.27 (s, 2 H); 2.27 (s, 3 H).

Intermediate 9 r5-methyl-4-(6-{4-r(trifluoromethyl)oxylphenyl)-3-pyridinyl)-3-isoxazolyllmethanol

A mixture of 300 mg (1.255 mmol) of (4-iodo-5-methyl-3-isoxazolyl)methanol (prepared according to the procedure described in WO2007/138048, Intermediate 22), 333 mg (3.14 mmol) of Na₂CO₃ and 53.4 mg (0.251 mmol) of 10% palladium on activated carbon (wet) in 2.13 ml of ethanol was deoxygenated by bubbling argon for 30 min. The mixture was heated to 85⁰C under argon atmosphere and a solution of 462 mg (1.632 mmol) of (6-{4- [(trifluoromethyl)oxy]phenyl}-3-pyridinyl)boronic acid (Intermediate 13) in 12.78 ml of ethanol and 1 ml of toluene (previously deoxygenated by bubbling argon for 30 min) were added dropwise during 1.5 h. The reaction mixture was stirred at 85⁰C under argon for 3h, then it was allowed to cool to rt. The ethanolic solutions were combined and concentrated under vacuum, then the crude was partitioned between te/f-butyl methyl ether and 0.5N NaOH. The organic layer was washed with 0.5N NaOH, 10% Na₂S₂O₅, water and brine, dried over Na₂SO₄, filtered and evaporated to lead a crude, which was dissolved in 10 ml of te/t-butyl methyl ether. Heptane (20 ml) was added and the solvents evaporated in vacuum to a volume of approx 20 ml. The operation was repeated by adding 10 ml of heptane and the solvent removed under reduced pressure to a volume of approx 20 ml, then it was left at room temperature for 1 h. The solid was filtered, washed with heptane and dried under vacuum to afford 306 mg of the title compound. 1H NMR (δ, ppm, DMSO-d₆ ): 8.84-8.78 (m, 1 H); 8.26 (d, 2H); 8.18-8.01 (m, 2H); 7.49 (d, 2H); 5.55 (t, 1 H); 4.54 (d, 2H); 2.51 (s, 3H).

Intermediate 10

2-(hvdroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy1phenyl)-3,3'-bipyridin-4(1 H)-one

1 ) Acetylation step

To a mixture of 5 g (14.27 mmol) of [5-methyl-4-(6-{4-[(trifluoromethyl)oxy]phenyl}-3- pyridinyl)-3-isoxazolyl]methanol (Intermediate 9) and 5.45 g (128 mmol) of lithium chloride in 200 ml of tetrahydrofuran anhydrous under argon were added 6.31 ml (44.2 mmol) of diisopropylamine, the mixture was cooled at -78⁰C and 21.89 ml (35.7 mmol) of n-Bul_i in hexane were added dropwise. The reaction was stirred at -78⁰C for 1.5h, then 2.124 ml (19.98 mmol) of N-methoxy-N-methylacetamide was added dropwise. After 45min of stirring under Ar at -78⁰C, a second portion of 0.91 ml (8.56 mmol) of N-methoxy-N- methylacetamide was added, maintaining the reaction mixture at -78⁰C for 2h. The reaction was allowed to reach O⁰C, then it was quenched dropwise with 1 N HCI and stirred overnight at rt. The reaction mixture was partitioned between tBuOMe and 1 N HCI. The organic phase was washed with 1 N HCI, H₂O, 10% NaHCO₃, H₂O and sat. NaCI, dried over sodium sulfate and evaporated in vacuo to afford 6.05g of the acetylated intermediate which was used in next step without further purification.

2) Reductive Rearrangement. Hvdroqenation step

6.05 g of the acetylated intermediate were dissolved in 300ml of EtOH and 1.O g (0.471 mmol) of 10% Pd(C) wet were added under nitrogen atmosphere. The mixture was hydrogenated overnight (Parr Hydrogenator, 2 bar H₂). The solids were removed by filtration through a 25mm syringe filter (Nylon 0.45 μm) washing with EtOH and the filtrate and washes combined and evaporated to dryness to give a crude which was triturated with CH₃CN. The solid was filtered, washed with CH₃CN and dried under vacuum to afford 3.83 g of the title compound.

¹H NMR (δ, ppm, DMSO-d₆): 1 1.16 (bs, 1 H); 8.49 (m, 1 H); 8.23 (d, 2H); 8.00 (m, 1 H); 7.75 (m, 1 H); 7.48 (d, 2H); 6.02 (s, 1 H); 5.59 (bs, 1 H); 4.27 (s, 2H); 2.27 (s, 3H). [ES MS] m/z: 377 [M+H]⁺.

Intermediate 11 r(4-{6-r2-fluoro-4-(trifluoromethyl)phenyll-3-pyridinyl)-5-methyl-3-isoxazolyl)methanol

Intermediate 1 1 was prepared using an analogous procedure to that used to prepare Intermediate 9, replacing Intermediate 13 with(6-[2-fluoro-4-(trifluoromethyl)phenyl]-3- pyridinyl)boronic acid (Intermediate 3).

¹H NMR (δ, ppm, DMSO-d₆ ): 8.90 (s, 1 H); 8.22 (t, 1 H); 8.12 (d, 1 H); 7.97 (d, 1 H); 7.86 (d, 1 H); 7.74 (d,1 H); 5.56 (t, 1 H); 4.56 (d, 2H); 2.52 (s, 3H). [ES MS] m/z: 353 [M+H]⁺.

Intermediate 12 6'-[2-fluoro-4-(trifluoromethyl)phenyl1-2-(hvdroxymethyl)-6-methyl-3,3'-bipyridin-4(1 H)-one

Method A:

Intermediate 12 was prepared using an analogous procedure to that used to prepare

Intermediate 10, replacing [5-methyl-4-(6-{4-[(trifluoromethyl)oxy]phenyl}-3-pyridinyl)-3- isoxazolyl]methanol (Intermediate 9) with [(4-{6-[2-fluoro-4-(trifluoromethyl)phenyl]-3- pyridinyl}-5-methyl-3-isoxazolyl)methanol (Intermediate 1 1 ).

¹H NMR (δ, ppm, DMSOd₆ ): 11.21 (bs, 1 H); 8.58 (s, 1 H); 8.21 (t, 1 H); 7.95-7.69 (m, 4H);

6.03 (s, 1 H); 5.61 (bs, 1 H); 4.28 (s, 2H); 2.27 (s, 3H). [ES MS] m/z: 379 [M+H]⁺.

Method B: 1 ) Acetylation step

To a solution 45 g (128 mmol) of (4-{6-[2-fluoro-4-(trifluoromethyl)phenyl]-3-pyridinyl}-5- methyl-3-isoxazolyl)methanol (Intermediate 11 ) in1.5 L Tetrahydrofuran anhydrous (THF) in a 1 OL double jacket reactor under Argon atmosphere were added 48.7 g (1150 mmol) of anhydrous Lithium chloride, then 60 ml (421 mmol) of Diisopropylamine were added dropwise and the mixture was cooled to -58⁰C. 148 ml of n-BuLi solution (2.4M in hexanes, 356 mmol) were added dropwise for 1 h and the reaction was stirred at -58⁰C for 2h. Then 19.01 ml (179 mmol) of N-methoxy-N-methylacetamide were added dropwise for 30min and the reaction mixture was stirred at -58⁰C under Argon for 1 h. Freshly prepared lithium diisopropylamide (9.9mmol of diisopropylamine and 9.0mmol of n-BuLi solution 2.4M in hexanes) in 90 ml of anhydrous tetrahydrofuran at O⁰C was added dropwise and the reaction mixture stirred at -58⁰C for 45min, then 2.0 ml (18.81 mmol) of N-methoxy-N- methylacetamide were dropwise added and the reaction stirred at -58⁰C for 45 min. It was quenched dropwise with 0.9L of 2N hydrochloric acid while the temperature was controlled to reach -3O⁰C, then it was warmed to rt and stirred for 30 min. The reaction mixture was partitioned between 4L of EtOAc and 1.6L of 1 N HCI and left without stirring overnight. The layers were separated and the organic one was washed with 2.5L of 1 N HCI, 2.5L of H₂O, 2.5L of 10% NaHCO₃, 2.5L of H₂O and 2.5L of sat. NaCI, dried over anhydrous sodium sulfate, filtered and evaporated in vacuo to give 49.5g of the acetylated intermediate.

2) Reductive Rearrangement. Hvdroqenation step

49.5g of the crude acetylated intermediate were hydrogenated in two batches (25g and 24.5g) using the same procedure as described above. General procedure:

25 g of the acetylated intermediate were dissolved in 1.1 L of MeOH and 5 g (2.35 mmol) of 10% Pd(C) wet (it contains approx 50% water) were added under nitrogen atmosphere.

The mixture was hydrogenated for 18h (Parr apparatus, 2 bar H₂). A lot of white solid was observed in the reaction vessel. 0.5 L of Dichloromethane were added and the mixture stirred under nitrogen atmosphere until the white solid was completely dissolved.

The solids were removed by filtration through Whatman filter paper washing with 1 :1 dichloromethane/methanol and the filtrate and washes combined and again filtered through Nylon membrane (0.45 μm). Solvents were removed under vacuum to a volume of approx 500 ml, then EtOH (500 ml) was added and solvent removed again under reduced pressure to a volume of approx 400 ml, then it was left in the fridge overnight.

The solid was filtered using the minimal amount of cold ethanol to collect all the solid.

After drying under suction, the solid was washed with ethyl acetate (75 ml) and dried in a vacuum oven at 4O⁰C overnight to afford 18.28 g of the title compound.

The second hydrogenation was carried out in the same way starting from 24.5g of the acetylated intermediate to afford 17.98 g of the title compound.

¹H NMR (δ, ppm, DMSO-d₆ ): 11.21 (bs, 1 H); 8.60-8.54 (m, 1 H); 8.21 (t, 1 H); 7.95-7.69 (m, 4H); 6.04 (s, 1 H); 5.60 (bs, 1 H); 4.28 (s, 2H); 2.27 (s, 3H). [ES MS] m/z: 379 [M+H]⁺.

Intermediate 13 (6-{4-[(trifluorornethyl)oxy1phenyl)-3-pyridinyl)boronic acid

Intermediate 13 was prepared using an analogous procedure to that used to prepare

Intermediate 3 (Method B, step 2), replacing 5-bromo-2-[2-fluoro-4-

(trifluoromethyl)phenyl]pyridine with 5-bromo-2-{4-[(trifluoromethyl)oxy]phenyl}pyridine (Intermediate 1 ).

H-NMR (δ, ppm, DMSO-d₆): 8.96 (s, 1 H); 8.38 (s,2H); 8.29-8.16 (m, 3H); 7.97 (d, 1 H); 7.47 (d, 2H). [ES MS] m/z: 284 [M+H]

Example 1

5-chloro-2-(hvdroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy1phenyl)-3,3'-bipyridin- 4(1 HVone

Method A:

200mg of 2-(hydroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-

4(1 H)-one were dissolved in 12 mL of DCM and 10 mL of MeOH under nitrogen at room temperature. This solution was cooled to 0 ⁰C and 40.8 mg of trichloroisocyanuric acid were added under nitrogen at 0 ⁰C. After 2 h, additional 12.2 mg of trichloroisocyanuric acid were added. The reaction was allowed to stir at up to 5 ⁰C, it was filtered through a nylon membrane, the filtrate was concentrated to dryness and the solid residue was triturated with saturated sodium carbonate, filtered and washed with diethyl ether and acetonitrile. The resulting solid was dried under vacuum to afford 106 mg of an off-white solid.

Similar reactions were run with 126 and 50 mg of 2-(hydroxymethyl)-6-methyl-6'-{4- [(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1 H)-one to obtain two further batches of crude product. All the batches of the crude product were put together to purify by flash master (10 g, Sill cartridge, eluting with DCM:MeOH) to afford 50 mg of the title compound.

Method B: To a stirred solution of 4.85 g (12.89 mmol) of 2-(hydroxymethyl)-6-methyl-6'-{4- [(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1 H)-one (Intermediate 10) in 150 ml of dichloromethane and 75 ml of methanol were added under nitrogen at O⁰C 1.225 (5.27 mmol) g of trichloroisocyanuric acid portionwise. The reaction mixture was stirred at 0 ⁰C for 1 h. The reaction mixture was filtered and concentrated, the residue was stirred with 5% Na₂CO₃ solution for 1 h, filtered and washed with H₂O, this solid was dried in vacuum at 40 ⁰C overnight. The solid was triturated with AcOEt to afford 4.24 g of the title compound.

¹H NMR (δ, ppm, DMSO-d₆ ): 1 1.69 (bs, 1 H); 8.54-8.50 (m, 1 H); 8.25 (d, 2H); 8.03 (d, 1 H); 7.78 (dd, 1 H); 7.49 (d, 2H); 5.67 (s, 1 H); 4.28 (s, 2H); 2.49 (s, 3H). [ES MS] m/z: 41 1 [M+H]⁺.

Example 2

5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl1-2-(hvdroxymethyl)-6-methyl-3,3'-bipyridin- 4(1 H)-one

Method A:

A solution of 300 mg (0.7 mmol) of 6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2- (hydroxymethyl)-6-methyl-3,3'-bipyridin-4(1 /-/)-one (Intermediate 12), 73.7 mg (0.3 mmol) of trichloroisocyanuric acid in 4 ml of dichloromethane and 4 ml of methanol at 0 ⁰C under nitrogen atmosphere were stirred during 1 h and then warmed to at room temperature and stirred for a furher 1 h. After this time starting material was present so additional portions of trichloroisocyanuric acid were added until completion as follows: 18.4 mg (0.07 mmol) and stiired for 30 min, then 9.21 mg (0.04 mmol) and stirred for a further 30 min. The solvent was evaporated and the residue was triturated with sodium carbonate (10% ) and diethyl ether. The resulting solid was purified by flash chromatography affording 280 mg of the title compound as a white solid.

¹H NMR (δ, ppm, DMSOd₆ ): 1 1.7 (1 H₁), 8.61 (s, 1 H), 8.22 (t, 1 H ), 7.9-7.8 (m, 3H), 7.74 (d, 1 H), 5.67 (1 H), 4.29 (s, 2 H), 2.49 (s, 3 H). [ES MS] m/z: 413 [M+H]⁺.

Method B:

96.6 g (255 mmol) of 6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2-(hydroxymethyl)-6-methyl-

3,3'-bipyridin-4(1 H)-one (Intermediate 12) were dissolved at room temperature in 5 L of a mixture 2:1 DCM / MeOH in a 1OL double jacket reactor under nitrogen atmosphere. This solution was cooled down to 0 ⁰C and 24.2 g (104 mmol) of Trichloroisocyanuric acid were then added portionwise. The reaction mixture was stirred at O⁰C for 1 h. Solids were removed by filtration through a Nylon membrane (0.45 μm) washing with 2:1 dichloromethane/methanol mixture. The filtrate and washes were combined and concentrated under vacuum until only methanol was left (500ml approx.). 5% aqueous Na₂CO₃ solution (3L) was added, the organic solvents removed under vacuum and the suspension stirred for 3h. Solids were then filtered, washed with 5% Na₂CO₃ (3x0.3L) and water (2x0.3L). The solid obtained was dried in the vacuum oven at 4O⁰C overnight, then washed with ethyl acetate (4x0.3L) and water (2x0.3L), and dried in the vacuum oven again at 4O⁰C overnight to yield 84.91 g of the title compound as a whitish solid.

¹H NMR (δ, ppm, DMSO-d₆ ): 11.73 (bs, 1 H); 8.60 (d, 1 H); 8.22 (t, 1 H); 7.96-7.79 (m, 3H); 7.74 (d, 1 H); 5.68 (t, 1 H); 4.29 (d, 2H); 2.48 (s, 3H). [ES MS] m/z: 413 [M+H]⁺.

Intermediate 14

{5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl1-6-methyl-4-oxo-1 ,4-dihvdro-3,3'-bipyridin-2- vDmethyl bis(phenylmethyl) phosphate

To a solution of 140 mg (0.33 mmol) of 5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2- (hydroxymethyl)-6-methyl-3,3'-bipyridin-4(1 H)-one (Example 2) in 8.5 ml of THF anh. at O⁰C was added 7 mg (0.8 mmol) of lithium hydride. The suspension was allowed to react under argon at r. t. overnight. The mixture was cooled to 0 ⁰C and 219 mg (0.4 mmol) of tetrabenzyl pyrophosphate was added portionwise. Once the addition was finished the suspension was allowed to react at 0 ⁰C for 90 min and then for 4 h at room temperature. The reaction was then cooled at 0 ⁰C and another 5.3 mg (0.6 mmol) of LiH were added. The mixture was stirred overnight at r.t.. The reaction mixture was quenched with 1 N HCI (4 ml) and partitioned between ethyl acetate (20 ml) and water (20 ml). The layers were separated and the organic phase was washed with aq. 5% Na₂CO₃ (3x20 ml), 1 N HCI (20 ml) and NaCI sat. (20 ml) and dried with MgSO₄. The solvent was evaporated and the residue was purified by flash chromatography affording 200 mg of the title compound.

¹H NMR (δ, ppm, CDCI₃ ): 10.7 (s, 1 H); 8.51 (s, 1 H), 8.17 (t, 1 H); 7.86 (d, 1 H); 7.74 (d, 1 H); 7.55 (d, 1 H); 7.45 (d, 1 H); 7.32-7.26 (m, 10H); 5.04 (d, 2H); 4.65 (d, 2H); 2.43 (s, 3H). [ES MS] m/z: 673 [M+H]⁺.

Intermediate 15

(5-chloro-6-methyl-4-oxo-6'-{4-r(trifluoromethyl)oxylphenyl)-1 ,4-dihvdro-3,3'-bipyridin-2- vDmethyl bis(phenylmethyl) phosphate bipyridin-2-yl)methyl bis(phenylmethyl) phosphate

Intermediate 15 was prepared using an analogous procedure to that used to prepare Intermediate 14, replacing 5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2- (hydroxymethyl)-6-methyl-3,3'-bipyridin-4(1 H)-one (Example 2) with 2-(hydroxymethyl)-6- methyl-6'-{4-[(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1 H)-one (Example 1 ). ¹H NMR (δ, ppm, DMSO-d₆ ): 12.16 (s, 1 H); 8.49 (s, 1 H), 8.21 (d, 2H); 7.98 (d, 1 H); 7.73 (d, 1 H); 7.49 (d, 2H); 7.23 (m, 10H); 4.90 (d, 4H); 4.83 (d, 2H); 2.42 (s, 3H). [ES MS] m/z: 671 [M+H]⁺.

Example 3

{5-chloro-6'-r2-fluoro-4-(trifluoromethyl)phenyll-6-methyl-4-oxo-1 ,4-dihvdro-3,3'-bipyridin-2- vDmethyl dihvdroqen phosphate

A suspension of 40 mg (0.05 mmol) of {5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-6- methyl-4-oxo-1 ,4-dihydro-3,3'-bipyridin-2-yl}methyl bis(phenylmethyl) phosphate

(Intermediate 14), 0.079 ml (0.83 mmol) of 1 ,4-cyclohexadiene and 6.3 mg (5.94 umol) of palladium on activated charcoal (10 %) in a mixture of dichloromethane (0.248 ml) and methanol (0.743 ml) was stirred for 3h. The catalyst was filtered and the filtrate was evaporated to dryness to give a solid which was triturated with te/f-butyl methyl ether (3 ml). The resulting solid was filtered and washed with te/f-butyl methyl ether affording 10 mg of the title compound.

¹H NMR (δ, ppm, DMSOd₆ ): 8.58 (s, 1 H); 8.23 (t, 1 H); 7.91-7.72 (m, 4H): 4.63 (d, 2H); 2.41 (s, 3H). [ES MS] m/z: 493 [M+H]⁺.

Example 4

{5-chloro-6-methyl-4-oxo-6'-{4-[(trifluoromethyl)oxy1phenyl)-1 ,4-dihvdro-3,3'-bipyridin-2- vDmethyl dihvdrogen phosphate

Example 4 was prepared according to an analogous procedure to that used to prepare Example 3, replacing {5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-6-methyl-4-oxo-1 ,4- dihydro-3,3'-bipyridin-2-yl}methyl bis(phenylmethyl) phosphate (Intermediate 14) with 5- chloro-2-(hydroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1 H)- one (Intermediate 15). 1H NMR (δ, ppm, DMSOd₆ ): 8.51 (d, 1 H); 8.26 (d, 2H), 8.03 (d, 1 H); 7.77 (dd, 1 H); 7.49 (d, 2H); 4.67 (d, 2H); 2.46 (s, 3H). [ES MS] m/z: 491 [M+H]⁺. The phosphate compound of Example 3 displayed an enhanced solubility in aqueous media compared to the compounds of Examples 1 and 2. Therefore, the phosphate compound of Examples 3 and 4 may, for example, be suitable for parenteral administration. Accordingly, Examples 3 and 4 may, for example, be particularly useful in the treatment of severe malaria. Advantageously, the compounds of Examples 3 and 4 are prodrugs that are hydrolysable in vivo to afford the compounds of Examples 1 and 2.

Comparator compounds

Three compounds are employed as comparator compounds and were tested in the same assays as the example compounds of the invention.

Compound X: Example 1 in WO 2007/138048: 3-chloro-6-(hydroxymethyl)-2-methyl-5-[4- ({4-[(trifluoromethyl)oxy]phenyl}oxy)phenyl]-4(1/-/)-pyridinone;

Compound Y: Example 27 in WO 2006/094799: 5-chloro-2,6-dimethyl-6'-{4-

[(trifluoromethyl)oxy]phenyl}-3,3'-bipyridin-4(1/-/)-one;

Compound Z: Example 58 in WO 2006/094799: 5-chloro-6'-[2-fluoro-4- (trifluoromethyl)phenyl]-2,6-dimethyl-3,3'-bipyridin-4(1 H)-one;

BIOLOGICAL ASSAYS The compounds of this invention may be tested in one of several biological assays to determine the concentration of compound which is required to have a given pharmacological effect. Assays 1 & 2

Determination of Ubiquinol-cytochrome bd (Cytbd) Oxi do reductase Activity for

Both Human (Assay 2) and Plasmodium falciparum (Assay 1) Enzymes

Introductory remarks

Ubiquinol-cytochrome c oxidoreductase is measured as the antimycin-sensitive decyubiquinol-cytochrome c oxidoreductase.

Ubiquinol-cytochrome c oxidoreductase is an essential respiratory enzyme, present in the inner mitochondrial membrane, which catalyzes the oxidation of ubiquinol and the concomitant reduction of cytochrome c in the mitochondrial respiratory chain.

2 Ferricytochrome c + Ubiquinol <=> 2 Ferrocytochrome c + Ubiquinone

Materials

Mitochondria

Isolated mitochondria from: HEK293 human cell line and Plasmodium falciparum 3D7 strain.

Assay Buffer Stock Solution 250 mM Sucrose (from 1 M stock)

50 mM KH₂PO₄ (from 100 mM stock, pH to 7.4 with KOH)

0.2 mM EDTA (from 0.5 M stock)

1 mM NaN₃ (from 1 M stock)

2.5 mM KCN (from 0.5 M Stock) This reaction buffer solution was freshly prepared on the day on the assay.

Decylubiquinol

Decylubiquinone (10 μmol) (obtained from Sigma, cat no. D791 1 ) was dissolved in 1 ml

Ethanol (acidified with 6 M HCI). A pinch of sodium borohydride was added. The mixture was shaken vigorously to reduce the yellow quinone to the colourless quinol. 3 ml of ether-cyclohexane (2:1 ) was added and the solution was mixed vigorously. The phases were allowed to separate, then the upper phase was removed into 1 ml of 2 M NaCI and mixed vigorously. The phases were allowed to separate again and then the upper phase was remove. The upper phase was dried under a stream of N₂ gas in a fume-cupboard. Ethanol (pH adjusted to 2 using HCI) was added to dissolve the ubiquinol and aliquots were stored at -80 ⁰C.

Cytochrome c

Cytochrome c (obtained from Sigma, catalogue number C2037) was made up to 10 mg/ml in water and stored in aliquots at -20 ⁰C. Negative control to test background

80 μM Myxothiazol (obtained from Sigma, catalogue number M5779) and 1 μM Antimycin (obtained from Sigma, catalogue number 642-15-9) was made up in ethanol and stored in aliquots at -20 ⁰C.

Assay Procedure

1. Mitochondria^* was diluted in the freshly prepared reaction buffer containing 50 μM cytochrome c. 2. 48 μl per well was added into a 96 well 1/2 area non-treated polystyrene plate.

3. The inhibitor compound being tested was added, the plate was shaken to ensure proper mixing and the reaction mixture was incubated for 10 minutes at room temperature. 800 nM myxothiazol and 100 nM antimycin A1 was added as a negative control to measure the non-enzymatic reduction of cytochrome c by decylubiquinol.

4. The reaction was started by the addition of 25 μM Decylubiquinol. (2.5 μl of a stock solution of 500 μM dissolved in ethanol).

5. The reduction of cytochrome c was followed by the increase in the absorbance at 550 nm for approximately 2 minutes.

^*The amount of mitochondria in the assay depended on the source. For mitochondria isolated from Plasmodium falciparum, the assay was run the assay with 40 μg/ml and for mitochondria from cell lines 15-20 μg/m was used.

Absorbance - Kinetic - % inhibition

Assay 3

Determination of Whole Cell IC₅₀ Values against Plasmodium falciparum I [³H]-

Hypoxanthine assay

Materials:

Culture medium

RPMI 1640 with 25mM HEPES, sodium bicarbonate and glutamine (GIBCO™ ret 52400- 025), supplemented with 10% of pooled human sera AB (Bioreclamation, HMSRM-AB) and 0.15 mM of hypoxanthine (from HT supplement x50, GIBCO™ ref. 41065). Human sera were decomplemented 30 min. at 56 ⁰C, aliquoted and stored frozen at -20 ⁰C until use. Complete medium was prepared fresh just before use and was pre-warmed at 37 ⁰C. Red Blood Cells

Red blood cells stock suspensions were prepared from whole blood bags coming from incomplete blood donation, provided by the Spanish Red Cross (<25 days after sampling). Whole blood was aliquoted and stored at 4 ⁰C. To prepare red blood cells, whole blood was washed 3 times with RPMI without serum by centrifugation (10 minutes at 2000 rpm, 650 xg). The upper phase, containing white blood cells was eliminated. Washed red blood cells were kept as a 50 % suspension in complete medium, and were stored for a maximum of 4 days at 4 ⁰C.

Solutions a) Medium A: (RPMI medium without hypoxanthine). 10% of human serum was added to RPMI medium with HEPES, sodium bicarbonate and glutamine. b) Medium B: (RPMI medium without hypoxanthine plus 1% DMSO). 10% of human serum and 1 % of DMSO were added to RPMI medium with HEPES, sodium bicarbonate and glutamine.

Compound Preparation a) Stock Solution: Test compounds were dissolved at 2 mg/ml in 100% DMSO on the day of the assay. When necessary, complete dilution was achieved by soft heating and sonication. b) Assay Solution: Before the test compounds were added to the parasites, the percentage of DMSO was reduced by further dilutions with complete medium without hypoxanthine. The final concentration of DMSO in the assay plates did not exceed 0.2%, a level for which detectable effects on parasite development have not been observed. To achieve that, the assay solution was prepared from the stock solution, 500 fold more concentrated than the final assay concentration required.

Parasite

Plasmodium falciparum strains were maintained in complete medium at an hematocrit value of 5% in continuous culture using a method adapted from Trager and Jensen [Trager, W. and J. B. Jensen, Human malaria parasites in continuous culture. Science, 1976. 193(4254): p. 673-675.]. The parasitemia was calculated by counting the percentage of parasitized erythrocytes by light microscopy. Thin films of blood were made every day from each culture flask, fixed with methanol and stained for 6 min. in Giemsa (Merck, ret 1.09204) at 5 % in buffered water pH 7.2 (Buffer tablets, Merck). The culture was maintained in culture flasks (canted neck, Corning) at 37 ⁰C, under low oxygen atmosphere (5 % CO₂, 5% O₂, 95 % N₂) with a daily change of medium and was diluted when parasitemia had reached about 5%. The parasite population was asynchronous and showed a regular rate of growth of 3 to 3.5 by day.

In vitro determination of ICm value of compounds against Plasmodium falciparum I [³HI- Hypoxanthine assay

To assess the effects of inhibitors on parasite metabolic activity, a modification of parasite [3H] Hypoxanthine incorporation assay described by Desjardins [Desjardins, R. E., et al., Quantitative assessment of antimalarial activity in vitro by a semiautomated microdilution technique. Antimicrob Agents Chemother, 1979. 16(6): p. 710-8.] was used. Inhibition of parasite growth was determined measuring how much tritiated hypoxanthine was uptaken by Plasmodium falciparum in vitro cultures.

Different in vitro cultures were treated with the tested compounds and the CCPM values obtained were compared with results obtained from control cultures. All values were normalised to percent of inhibition activity and a predicted IC₅₀ value was calculated along a linear trend using a concentration values near to 50% inhibition. Dose response curves were represented by fitting experimental values to a Non-lineal regression (sigmoidal dose-response curve) as:

Bottom + (Top - Bottom)

(l + 10^Zog/C5°-^χ )

where X is the logarithm of concentration, Y is the response (% of control cultures), Top were fixed to 100 and bottom to 0.

Drug dilution plate preparation. In round bottom 96 well plate, fill rows B to H were filled with 200 μl of medium B and row A was filled with 396 μl of medium B. 4 μl of each 50Ox concentrated drug solution was added in respective well of row A. Mixing was performed with a pipette.

To carry out serial dilutions, 200 μl was transferred from column 1 to column 2, mixed with a pipette and 200 μl was transfer to column 2 to column 3. Mixing and transferral was repeated respectively up to column 10. 200 μl was discarded from column 10. Different drug dilutions were disposed in each row of the plate. 50 μl was transferred from the drug dilution plate to a culture plate (a flat bottom 96 well plate), generating 2 replicas of each dilution.

Chloroquine and atovaquone were used as controls in the assays, disposed in only one of the plates. The maximum concentration in culture plate assay for chloroquine was 100ng/ml for sensitive strains and 4 jxg/ml for resistant strains. The maximum concentration for atovaquone was 12.8 ng/ml for sensitive strains and 20 μg/ml for resistant strains.

lnocula preparation.

25 ml per assay plate of pre-warmed medium A was prepared at 2.5% of hematocrit value, with 0.5% of parasitemia. 25 μl of [³H] hypoxanthine stock (1 mCi/ml) was added to 25 ml of inoculum to obtain a final concentration of 1 μCi/ml. A 2.5 ml per assay plate of pre-warmed medium A was prepared at 2.5% of hematorcrit value without the parasite. 2.5 μl of [³H] hypoxanthine stock (1 mCi/ml) was added to 2.5 ml of inoculum to obtain a final concentration of 1 μCi/ml.

Assay culture plate preparation and incubation

200 μl of tritiated parasitized red blood cells was transferred on columns 1 to 11 and on wells E-H of column 12, and 200 μl of tritiated non-parasitized red blood cells was transferred on wells A-D of column 12. Four drugs are tested in each plate (by replicate), with ten 2-fold serial dilutions located from column 1 to 10, with higher concentration in column 1 and lower in column 10. The plates were incubated for 48 h at 37 ⁰C with 5%CO₂, 5% O₂ and 95% N₂. After incubation the plates were frozen overnight at -80 ⁰C.

Harvesting cultures and measure of incorporated radioactivity.

The plates were thawed and the cells were harvested on glass fibre filters (Wallac 1450- 421 ) using a TOMTEC cell harvester. The filters were dried and a solid scintillation sheet (Meltilex ^® A, PerkinElmer ref: 1450-441) was melted and the incorporation of radioactivity was measured with a Microbeta Trilux 1450 LSC Luminescence Counter (Wallac, PerkinElmer) scintillation counter.

Data analysis

The CCPM counts were corrected subtracting the background value obtained from red blood cells incorporation, and the percentage of inhibition in each well was calculated using the following formula:

n . _r . , ., . . _{Λ nn} CCPM counts in each well x 100

% of inhibition = 100

CCPM counts of control culture

For each concentration of drug, the average value of the duplicate samples was calculated, and non-linear regression fit (sigmoidal dose-response curve) using GraphPad Prism software was adjusted to obtain an IC₅₀ value, corresponding to the concentration which inhibits 50% of parasite development. Assay 4

Determination of Cytotoxicity against human Hep G2 Whole Cell lines

Materials. Cells.

Hep G2: Human Caucasian hepatocyte carcinoma. This cell line was obtained from the European Collection of Cell Cultures (ECACC 85011430).

Culture medium^ Minimum Essential Medium Eagle (EMEM) with non-essential amino acids, with pyruvate Na, without L-glutamine. Cat. n°. 12-662 F (Bio- Whittaker).

Collagen solution type 1 from calf skin, cat. n° C 8919 (Sigma).

Trypsin-Versene mixture, cat. n° 17-161 E (Bio-Whittaker).

L-Glutamine 200 mM, cat, n° 289.1000 (Merck)

Foetal calf seum.

Foetal Clone II, Perbio, ref SH 30066.03

Cell maintenance. All the plastic culture flasks used were coated with 3% collagen type I in EMEM. The cell line was cultured in EMEM supplemented with 5% foetal calf serum and 2 mM L- glutamine (routine culture medium). Cells were grown in 75 cm² flasks with canted neck and incubated at 37 ⁰C, 5% CO₂ and 95% humidity.

When cells reached confluence they were removed from the flask by trypsinization, wherein (a) the medium was decanted and the monolayer was rinsed with EDTA 0.02% (Sigma E-651 1 ); (b) the washing solution was discarded; (c) Trypsin-EDTA solution was added to the monolayer; (d) the flask was incubated at 37 ⁰C for several minutes and the flask was tapped until cells detached and formed a single cell suspension; (e) the cell suspension was removed from the flask to a 50 ml tube and enough volume of routine culture medium was added to inactivate trypsin; (f) the tube was spun in a centrifuge at 1500 rpm for 5 minutes at room temperature; and (g) the confluent cultures were split 1 :3 to 1 :6. Compound Preparation

The test compounds were obtained dissolved in 100% DMSO. As DMSO damages cells, the percentage was reduced to 0.5% by diluting 1 :200 in culture medium; therefore the stock solution was 200-fold more concentrated than the highest final concentration in the cell culture. Briefly, dilutions were performed in the following steps.

1. Ten serial dilutions /4 in DMSO, from the mother solution at 2 mg/mL in DMSO in a microtiter plate.

2. Transfer 1.8 μl_ to a 96 well microplate, the "dilution plate", capacity of each well 400 μl_, previously filled with 360 μL/well of culture medium. The solubility of the compounds was checked in each set of concentrations. The five highest soluble concentrations from the dilution plate were tested in the assay.

3. Remove culture medium from the assay plate.

4. Transfer 150 μl_ from the selected wells in two replicates to the plate where cells had been seeded "assay plate".

In vitro determination of cytotoxicity of compounds against HepG2

1. The cells were detached cells by trypsin/versene as described above. The cells were suspended in routine culture medium and passed through a stainless steel cell dissociation sieve to make a single cell suspension.

2. Viable cells were counted in a hemocytometer using trypan blue. Using a multichannel pipette 10,000 cells were dispensed in 100 μl of medium per well (black 96 well microplate with clear bottom, previously collagen type I coated), except for column 11 that was filled with growth medium without cells. 3. The microplate was Incubated for 24 hours until the cells formed a third confluent monolayer. It is important that cells are in an exponential growth phase for the cytotoxicity assay. This incubation period allowed for cell recovery and adherence.

4. A range dose of test substance was made up by preparing serial dilutions Vi from the mother solution (2 mg/mL in DMSO) in a 96 well microplate. All dilutions were performed in DMSO to avoid precipitation of the test compounds.

5. From each of these dilutions, 1.8 μl_ was transferred to a 96 well microplate, the "dilution plate", capacity of wells 400μl, previously filled with 360 μL/well of culture medium. Ten serial dilutions were prepared.

6. The solubility of the compounds was checked in each set of concentrations. The five highest soluble concentrations from the dilution plate were tested in the assay.

7. The culture medium was removed from the assay plate and 150 μL was transfer from the selected concentrations of the dilution plate in two replicates.

8. 150 μL of 0.5 % DMSO in culture medium was added to blank and growth control columns (1 1 and 12 respectively) to reach the same solvent concentration as the samples.

9. Cells were incubated in presence of the compounds for 24, 48 and 72 h at 37°C/5% CO₂/ 95% humidity. 10. A 0.004% resazurin solution was formulated by adding 60 ml Dulbecco's PBS to each tablet of resazurin. The tablet was allowed to dissolve by placing the container in a bath set at 37 ⁰C protected from light for approximately 30 minutes.

11. The plates were taken from the incubator. The medium was removed and 200 μl of fresh culture medium and 50 μl_ of resazurin solution were added to each well.

12. The plates were returned to the incubator for a further 1 ^ΛA hours. The plates were removed from the incubator and the fluorescence was left to stabilise at room temperature for 15 minutes protected from light.

13. Fluorescence was measured using a 96 well fluorescence plate reader at an excitation wavelength of 515 nm and an emission wavelength of 590 nm.

Data Analysis

The fluorescence value of each well was corrected by subtracting the background value (average of the column 11 ) from the absolute value. The percentages of inhibition were calculated relatively to the DMSO control wells average (column 12). For each compound, the average value of the duplicate samples was calculated.

Results of Assays i) Enzyme Assays 1 and 2 The compounds of Examples 1 and 2 and Comparative compounds X, Y and Z were tested in Assays 1 and 2.

Assay 2 (human enzyme assay): Both Examples 1 and 2 displayed an approximately ten fold reduction in activity against the human isolated mitochondrial Cytbd target compared to that of comparative compound X, and an approximately four to six-fold reduction in activity against the human isolated mitochondrial Cytbd target compared to that of comparative compounds Y and Z.

Assay 1 (parasite enzyme assay): Both Examples 1 and 2 were found to have good activity (less than 100 nM) against the Plasmodium falciparum isolated target. Example 2 was found to have an IC₅₀ Of approximately 30 nM in Assay 1.

ii) Whole cell Assays 3 and 4

The compounds of Examples 1-4 and Comparative compounds X, Y and Z were tested in

Assays 3 and 4.

Assay 4 (human whole cell assay): Examples 1-4 and Comparative compound Y displayed a reduced activity in the HepG2 cell line whole cell assay (at least two fold) compared to that of comparative compound X. Comparative compound Z displayed a substantial increase in activity in the HepG2 cell line whole cell assay (at least ten fold) compared to that comparative compound X.

Assay 3 (parasite whole cell assay): Examples 1-4 were found to have good activity (an IC₅₀ of less than 0.019 μg/ml) in the Plasmodium falciparum whole cell assay. Example 2 was found to have an IC₅₀ of approximately 0.002 ug/ml in Assay 3. The results of Assays 1-4 are summarised in the Table below:

Key to Table

Assays 1 and 2 - ICfsn in uM Assays 3 and 4 - ICm in ug/ml

*

IC₅₀<0.01 IC₅₀<0.1 +

**

0.0K IC₅₀<0. 1 O.K IC₅₀<0.5 ++

***

0.3< IC₅₀<0.9 5< IC₅₀<10 +++

****

3< IC₅₀<5 10< IC₅₀<30 ++++

NT Not tested 30< IC₅₀ +++++ Compounds showing i) high selectivity for Assay 1 over Assay 2, and/or ii) high selectivity for Assay 3 over Assay 4 may be considered to have an advantageous cytotoxicity profile. The results described above demonstrate that Examples 1-4 of the invention have a lower potency against a human target compared to known compounds whilst retaining good levels of activity against a parasitic target. Thus, the compounds of the present invention have been shown to have potential as agents for use in the chemotherapy of certain parasitic infections such as malaria, the compounds having an advantageous cytotoxicity profile.

Claims

1. A compound of Formula

wherein: each R¹ independently represents halo, CF₃ Or OCF₃;

R² represents H or a hydrolysable ester, phosphate or carbamate group;

2. A compound or pharmaceutically acceptable salt thereof according to claim 1 , wherein R¹ represents F, CF₃ Or OCF₃.

3. A compound or pharmaceutically acceptable salt thereof according to claim 1 or claim 2, wherein n represents 1 or 2.

4. A compound of Formula Ia:

Ia wherein:

R^1a represents H or F; R^1b represents CF₃ or OCF₃; R² represents H or a hydrolysable ester, phosphate or carbamate group; and X represents halo; or a pharmaceutically acceptable salt thereof.

5. A compound or pharmaceutically acceptable salt thereof according to claim 4, wherein either R^1a is F and R^1b is CF₃ or R^1a is H and R^1b is OCF₃

6. A compound or pharmaceutically acceptable salt thereof according to any one of claims 1 to 5, wherein X represents Cl.

7. A compound or pharmaceutically acceptable salt thereof according to any one of claims 1 to 6, wherein R² represents H or a hydrolysable phosphate group.

8. A compound according to claim 1 selected from: 5-chloro-2-(hydroxymethyl)-6-methyl-6'-{4-[(trifluoromethyl)oxy]phenyl}-3,3'- bipyridin-4(1 H)-one;

5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2-(hydroxymethyl)-6-methyl-3,3'- bipyridin-4(1 H)-one;

{5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-6-methyl-4-oxo-1 ,4-dihydro-3,3'- bipyridin-2-yl}methyl dihydrogen phosphate; and

{5-chloro-6-methyl-4-oxo-6'-{4-[(trifluoromethyl)oxy]phenyl}-1 ,4-dihydro-3,3'- bipyridin-2-yl}methyl dihydrogen phosphate, or a pharmaceutically acceptable salt thereof

9. A compound which is 5-chloro-6'-[2-fluoro-4-(trifluoromethyl)phenyl]-2- (hydroxymethyl)-6-methyl-3,3'-bipyridin-4(1 H)-one.

10. A compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 9 for use in medical therapy.

11. A compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 9 for use in the treatment of malaria.

12. Use of a compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 9 in the manufacture of a medicament for the treatment of malaria.

13. A method for the treatment of a human or animal subject suffering from malaria comprising administering to said human or animal subject an effective amount of a compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 9.

14. A compound or a pharmaceutically acceptable salt thereof according to claim 11 , a use according to claim 12 or a method according to claim 13, wherein malaria is caused by infection with Plasmodium falciparum.

15. A pharmaceutical composition comprising at a compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 9, in admixture with one or more pharmaceutically acceptable carrier and/or excipient.

16. A pharmaceutical composition according to claim 14 comprising a combination of a compound of Formula I or a pharmaceutically acceptable salt thereof and a further active therapeutic agent.