WO2011054947A1 - Thiadiazolidinedioxide p2x7 receptor antagonists - Google Patents

Abstract

The invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof wherein: R¹ is C_1-3alkyl or C₁fluoroalkyl-CH₂; R² is hydrogen, C_1-4alkyl, C₁fluoroalkyl-CH₂-, C_3-6cycloalkyl, C_3-6cycloalkyl-methyl-, optionally substituted benzyl, or optionally substituted heteroaryl-(CH₂)_n-, wherein n is 0 or 1, wherein in R₂ the benzyl is optionally substituted on the ring with one or two substituents independently being methyl, methoxy, fluorine or chlorine, and wherein in R² the heteroaryl-(CH₂)_n- optionally substituted on the heteroaryl ring with one or two substituents independently being C_1-3alkyl, CF₃, methoxy, a halogen atom, or cyano; and wherein: R³, R⁴, R⁵, R⁶ and R⁷ independently are hydrogen, a halogen atom, C_1-4alkyl, trifluoromethyl, or cyano, such that one or both of R³ and R⁷ is or are a group other than hydrogen.

Description

Thiadiazolidinedioxide P2X7 Receptor Antagonists

The present invention relates to thiadiazolidine derivatives which modulate P2X7 receptor function and are capable of antagonizing the effects of ATP at the P2X7 receptor ("P2X7 receptor antagonists"); to processes for their preparation; to pharmaceutical compositions containing them; and to the use of such compounds in therapy.

The P2X7 receptor is a ligand-gated ion-channel which is expressed in cells of the hematopoietic lineage, e.g. macrophages, microglia, mast cells, and lymphocytes (T and B) (see, for example, Collo, et al. Neuropharmacology, Vol.36, pp1277-1283 (1997)), and is activated by extracellular nucleotides, particularly adenosine triphosphate (ATP). Activation of P2X7 receptors has been implicated in giant cell formation, degranulation, cytolytic cell death, CD62L shedding, regulation of cell proliferation, and release of proinflammatory cytokines such as interleukin 1 beta (IL- 1 β) (e.g. Ferrari, et al., J. Immunol., Vol.176, pp3877-3883 (2006)) and tumour necrosis factor alpha (TNFa) (e.g. Hide, et al. Journal of Neurochemistry, Vol.75, pp965-972 (2000)). P2X7 receptors are also located on antigen presenting cells, keratinocytes, parotid cells, hepatocytes, erythrocytes, erythroleukaemic cells, monocytes, fibroblasts, bone marrow cells, neurones, and renal mesangial cells.

Furthermore, the P2X7 receptor is expressed by presynaptic terminals in the central and peripheral nervous systems and has been shown to mediate glutamate release in glial cells (Anderson, C. et al. Drug. Dev. Res., Vol.50, page 92 (2000)). The localisation of the P2X7 receptor to key cells of the immune system, coupled with its ability to release important inflammatory mediators from these cells suggests a potential role of P2X7 receptor antagonists in the treatment of a wide range of diseases including pain and neurodegenerative disorders. Recent preclinical in vivo studies have directly implicated the P2X7 receptor in both inflammatory and neuropathic pain (Dell'Antonio et al., Neurosci. Lett., Vol.327, pp87-90 (2002),.

Chessell, IP., et al., Pain, Vol.1 14, pp386-396 (2005), Honore et al., J. Pharmacol. Exp. Ther., Vol.319, p1376-1385 (2006)) while there is in vitro evidence that P2X7 receptors mediate microglial cell induced death of cortical neurons (Skaper, S.D., et al., Glia, Vol.54, p234-242 (2006)). In addition, up-regulation of the P2X7 receptor has been observed around β-amyloid plaques in a transgenic mouse model of

Alzheimer's disease (Parvathenani, L. et al. J. Biol. Chem., Vol.278(15), pp13309- 13317 (2003)). The present invention provides compounds which modulate P2X7 receptor function and are capable of antagonizing the effects of ATP at the P2X7 receptor ("P2X7 receptor antagonists").

In a first aspect of the invention, there is provided a compound of formula (I) or a pharmaceutically acceptable salt thereof

(I)

wherein:

R1 is C-|_3alkyl (e.g. methyl, ethyl or isopropyl) or C-|fluoroalkyl-CH2- (e.g.

CF3-CH2-); R2 is hydrogen, C-|_4alkyl (e.g. methyl, ethyl or isopropyl), C-|fluoroalkyl-CH2- (e.g. or CF3-CH2-, or CHF2-CH2- or CH₂F-CH2-), C3_6cycloalkyl, Cs.gcycloalkyl-methyl-, optionally substituted benzyl, or optionally substituted heteroaryl-(CH2)_n-, wherein n is 0 or 1 ,

wherein in R2 the benzyl is optionally substituted on the ring with one or two substituents independently being methyl, methoxy, fluorine or chlorine, and wherein in R2 the heteroaryl-(CH2)_n- is optionally substituted on the heteroaryl ring with one or two substituents independently being C-_|_3alkyl (e.g. methyl), CF3, methoxy, a halogen atom (e.g. fluorine or chlorine), or cyano; and wherein:

R3, R4, R5_J R6 _ANC| R7 independently are hydrogen, a halogen atom (e.g. chlorine or fluorine), C-_|_4alkyl (e.g. methyl), trifluoromethyl, or cyano,

such that one or both of R^ and R^ is or are a group other than hydrogen. As used herein, the term "alkyl" (when used as a group or as part of a group) means a straight or branched hydrocarbon chain containing the specified number of carbon atoms. For example, C_1-6 alkyl means a straight or branched hydrocarbon chain containing at least 1 and at most 6 carbon atoms. Examples of alkyl include, but are not limited to: methyl (Me), ethyl (Et), n-propyl, i-propyl, t-butyl, n-hexyl and i-hexyl.

As used herein, the term "C3_gcycloalkyl" means a 3 to 6 membered saturated carbocyclic ring, for example cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. As used herein, the term "halogen" or "a halogen atom" means, unless otherwise stated, a group being fluorine, chlorine, bromine or iodine.

The term "heteroaryl" as used herein means a 5 to 6 membered monocyclic aromatic ring containing 1 to 3 heteroatoms independently being oxygen, nitrogen or sulfur. The heteroaryl can for example be thienyl, furanyl, pyrrolyl, triazolyl, imidazolyl, oxazolyl, thiazolyl, oxadiazolyl, isothiazolyl, isoxazolyl, thiadiazolyl, pyrazolyl, pyrimidyl, pyridazinyl, pyrazinyl or pyridyl. The heteroaryl can in particular be pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl. The heteroaryl, e.g. as described above, may be linked to the remainder of the molecule via (i) a carbon atom or, (ii) via a suitable nitrogen atom (when a nitrogen atom is present and is available for covalent bonding to the remainder of the molecule without becoming positively charged), except where otherwise indicated.

It is to be understood that the present invention covers and discloses all possible combinations of particular, preferred, suitable, or other embodiments of groups or features (e.g. of R^ , R^, R3, R _; R5_j R6_j R7 and/or n), e.g. all possible combinations of embodiments of different groups or features, which embodiments are described herein.

In particular embodiments of the invention, R^ is C-|_3alkyl or CF3-CH2-; more particularly C-|_3alkyl; still more particularly methyl, ethyl or isopropyl.

Preferably, R^ is methyl or ethyl. In particular embodiments of the invention, R2 is hydrogen, C-|_4alkyl (e.g. methyl, ethyl or isopropyl), C-|fluoroalkyl-CH2- (e.g. or CF3-CH2-, or CHF2-CH2- or

CH2F-CH2-), C3_gcycloalkyl, C3_gcycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-, wherein n is 0 or 1 (e.g. 0).

In more particular embodiments, R2 is hydrogen, C-|_3alkyl (e.g. methyl, ethyl or isopropyl), C-|fluoroalkyl-CH₂- (e.g. or CF₃-CH₂-, or CHF2-CH₂- or CH₂F-CH2-), C3_gcycloalkyl, C3_gcycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-, wherein n is 0 or 1 (e.g. 0), and wherein the heteroaryl is pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl.

In more particular embodiments, R2 is hydrogen, C-|_3alkyl (e.g. methyl, ethyl or isopropyl), C-|fluoroalkyl-CH₂- (e.g. or CF₃-CH₂-, or CHF2-CH₂- or CH₂F-CH2-), C3_gcycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-_! wherein n is 0 or 1 (e.g. 0), and wherein the heteroaryl is pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl.

In still more particular embodiments, R2 is hydrogen, C-|_3alkyl (e.g. methyl, ethyl or isopropyl), C3_4cycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-, wherein n is 0 or 1 (e.g. 0),

wherein the heteroaryl is pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl, optionally substituted on the heteroaryl ring with one or two (e.g. one) substituents

independently being methyl, CF3, methoxy, fluorine, chlorine, or cyano.

In yet more particular embodiments, R2 is hydrogen, C-|_3alkyl (e.g. methyl, ethyl or isopropyl; such as methyl or ethyl), or optionally substituted heteroaryl,

and wherein the heteroaryl is pyridinyl or pyrimidinyl, optionally substituted on the heteroaryl ring with one substituent independently being methyl, CF3, methoxy, fluorine or chlorine. In particular embodiments, n is 0.

In particular embodiments, when R2 is optionally substituted heteroaryl-(CH2)_n-, then the heteroaryl-(CH2)_n- is optionally substituted on the heteroaryl ring with one or two (e.g. one) substituents independently being methyl, CF3, methoxy, fluorine, chlorine, or cyano.

Preferably, is hydrogen, methyl or ethyl; in particular methyl.

In particular embodiments of the invention, R3, R^, R5_J R6 _ANC| R7 independently are hydrogen, a halogen atom (e.g. chlorine or fluorine), methyl or trifluoromethyl, such that one or both of R^ and R⁷ is or are a group other than hydrogen.

In a particular embodiment of the invention,

R3 and R^ both are hydrogen,

R5 is hydrogen, chlorine or fluorine,

R6 is hydrogen, chlorine, fluorine or trifluoromethyl, and

R⁷ is chlorine, fluorine, methyl or trifluoromethyl.

In this case, more particularly,

R3 and R4 both are hydrogen,

R5 is hydrogen, chlorine or fluorine,

R⁶ is hydrogen, chlorine, fluorine or trifluoromethyl, and

R⁷ is chlorine or methyl,

wherein one or both of R^ and R^ is or are other than hydrogen.

In this case, preferably,

R3 and R^ both are hydrogen,

R⁷ is chlorine or methyl, and

either R^ is hydrogen, and R^ is trifluoromethyl,

or R5 is chlorine, and R^ is hydrogen,

or R5 is fluorine, and R^ is hydrogen or fluorine.

In an alternative particular embodiment of the invention,

R3 is hydrogen, chlorine, fluorine or methyl,

R4 is hydrogen, R5 is chlorine or fluorine,

R6 is hydrogen, and

R⁷ is chlorine or methyl. In this case, preferably,

R3 is hydrogen, chlorine, fluorine or methyl,

R4 is hydrogen,

R5 is chlorine,

R6 is hydrogen, and

R⁷ is chlorine or methyl.

Preferably,

R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R⁷ is chlorine;

R3, R^ and R6 each are hydrogen and R^ and R⁷ both are chlorine;

R3 and R^ both are hydrogen, R^ and R^ both are fluorine, and R⁷ is chlorine;

R3, R^ and R^ each are hydrogen, R^ is trifluoromethyl, and R⁷ is methyl;

R3 and R4 both are hydrogen, R^ is fluorine, R^ is trifluoromethyl, and R⁷ is chlorine;

R3 is methyl, R^ and R^ both are hydrogen, and R^ and R⁷ both are chlorine;

R³, R5 and R⁷ each are chlorine, and R4 and R6 both are hydrogen;

R³, R4 and R⁵ each are hydrogen, R6 is trifluoromethyl, and R⁷ is fluorine;

R3, R4 and R6 each are hydrogen, R^ is fluorine, and R⁷ is chlorine;

R3, R4 and R^ each are hydrogen, R^ is chlorine, and R⁷ is methyl;

R3, R4 and R^ each are hydrogen, R6 is chlorine, and R⁷ is methyl;

R3 and R4 both are hydrogen, R^ is fluorine, and R^ and R⁷ both are chlorine;

R³, R4 and R⁵ each are hydrogen and R^ and R⁷ both are chlorine; or

R3 is fluorine, R4 and R6 both are hydrogen, and R^ and R⁷ both are chlorine.

More preferably,

R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R⁷ is chlorine;

R3, R4 and R^ each are hydrogen and R^ and R⁷ both are chlorine;

R3 and R⁴ both are hydrogen, R^ and R^ both are fluorine, and R⁷ is chlorine;

R3, R^ and R^ each are hydrogen, R6 is trifluoromethyl, and R⁷ is methyl; R3 and both are hydrogen, is fluorine, is trifluoromethyl, and R^ is chlorine; R3 is methyl, R^ and R^ both are hydrogen, and R^ and R^ both are chlorine; or R³, R5 and R7 each are chlorine, and R4 and R6 both are hydrogen, Still more preferably,

R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R7 is chlorine;

R3, R4 and R^ each are hydrogen and R^ and R^ both are chlorine; or

R3 and R4 both are hydrogen, R^ and R^ both are fluorine, and R7 is chlorine,

In one embodiment of the invention, there is provided a compound whose chemical name and/or structure is as described in Example 1 or Example 2, or a

pharmaceutically acceptable salt thereof.

Antagonists of P2X7 may be useful in preventing, treating, or ameliorating a variety of pain states (e.g. neuropathic pain, chronic inflammatory pain, and visceral pain), inflammation and neurodegeneration, in particular Alzheimer's disease. P2X7 antagonists may also constitute useful therapeutic agents in the management of rheumatoid arthritis.

Compounds of the present invention which modulate P2X7 receptor function and are capable of antagonizing the effects of ATP at the P2X7 receptor ("P2X7 receptor antagonists") may be competitive antagonists, inverse agonists, or negative allosteric modulators of P2X7 receptor function.

Certain compounds of formula (I) may in some circumstances form acid addition salts thereof. It will be appreciated that for use in medicine compounds of formula (I) may be used as salts, in which case the salts should be pharmaceutically acceptable. Pharmaceutically acceptable salts include those described by Berge, Bighley and Monkhouse , J. Pharm. Sci., 1977, 66, 1-19. Basic compounds of formula (I) may form salts with pharmaceutically acceptable acids including inorganic and organic acids. Such acids include acetic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethanesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric, p-toluenesulfonic acid, and the like. Examples of pharmaceutically acceptable salts include those formed from maleic, fumaric, benzoic, ascorbic, pamoic, succinic, hydrochloric, sulfuric,

bismethylenesalicylic, methanesulfonic, ethanedisulfonic, propionic, tartaric, salicylic, citric, gluconic, aspartic, stearic, palmitic, itaconic, glycolic, p-aminobenzoic, glutamic, benzenesulfonic, cyclohexylsulfamic, phosphoric and nitric acids.

The compounds of formula (I) may be prepared in crystalline or non-crystalline form, and, if crystalline, may optionally be solvated, e.g. as the hydrate. This invention includes within its scope solvates (e.g. hydrates), such as stoichiometric solvates (e.g. hydrates), of the compounds or salts thereof, as well as compounds containing variable amounts of solvent (e.g. water).

Certain compounds of formula (I) or salts thereof are capable of existing in stereoisomeric forms (e.g. diastereomers and enantiomers) and the invention extends to each of these stereoisomeric forms and to mixtures thereof including racemates. The different stereoisomeric forms may be separated one from the other by the usual methods, or any given isomer may be obtained by stereospecific or asymmetric synthesis. The invention also extends to any tautomeric forms and mixtures thereof.

A further particular aspect of the present invention provides a compound of formula (IA) or a pharmaceutically

(IA)

wherein:

R1 , R2, R3_j R4_; R5_j R6_{j anc}| R7 _{are as} defined herein for the compound of formula (I) or the salt thereof,

and wherein more than 50% (e.g. more than 70%, in particular more than 90%, such as more than 95%) by molarity of the compound of formula (IA) or the

pharmaceutically acceptable salt thereof has the stereochemistry shown at the thiadiazolidine ring-carbon atom which is directly bonded to the R¹-bearing ring- nitrogen atom. Preparation of compounds

(I)

Compounds of formula (I), wherein the variables are as defined herein, and salts thereof may be prepared by the methodology described hereinafter, constituting a further aspect of this invention.

A process according to the invention, for preparing a compound of formula (I) or a pharmaceutically acceptable salt thereof, comprises process (a), (b) or (c):

(a) Coupling of a carboxylic acid of formula (2) (or an activated derivative thereof) with an amine of formula (3) (see Scheme 1 below), wherein R¹, R², R³, R⁴, R⁵, R⁶, and R⁷ are as defined above. Compounds (2) and (3) are optionally protected.

(b) Deprotecting a compound of formula (I) which is protected. Examples of protecting groups and the means for their removal can be found in T.W. Greene and P.G.M. Wuts 'Protective Groups in Organic Synthesis' (Wiley-lnterscience, 4th Ed. 2006).

(c) Interconversion of compounds of formula (I) to other compounds of formula (I). Examples of conventional interconversion procedures include, for example, epimerisation, oxidation, reduction, alkylation, aromatic substitution, nucleophilic substitution, amide coupling and ester hydrolysis.

Scheme 1

In process (a), shown in Scheme 1 , the coupling of an acid of formula (2) and an amine of formula (3) typically comprises the use of an activating agent, such as N-(3- dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride or polymer-supported carbodiimide, 1-hydroxybenzotriazole (HOBT) or 1 -hydroxy-7-azabenzotriazole (HOAt), and optionally a suitable base such as a tertiary alkylamine (e.g.

diisopropylethylamine, N-ethyl morpholine, triethylamine) or pyridine, in a suitable solvent such as DMF and/or dichloromethane and at a suitable temperature e.g. between 0°C and room temperature. Alternatively the coupling of (2) and (3) may be accomplished by treatment with 0-(7-azabenzotriazol-1-yl)-N,N,N',N'- tetramethyluronium hexafluorophosphate and a suitable tertiary alkylamine such as diisopropylamine in a suitable solvent such as dimethylformamide at a suitable temperature such as room temperature. Alternatively, the compound of formula (2) may be employed as an activated derivative (e.g. acid chloride, mixed anhydride, active ester (e.g. O-acyl-isourea)), and under such circumstances process (a) typically comprises treatment of said activated derivative with an amine (Ogliaruso, M.A.; Wolfe, J.F. in The Chemistry of Functional Groups (Ed. Patai, S.) Suppl.B: The Chemistry of Acid Derivatives, Pt. 1 (John Wiley and Sons, 1979), pp442-8;

Beckwith, A.L.J, in The Chemistry of Functional Groups (Ed. Patai, S.) Suppl.B: The Chemistry of Amides (Ed. Zabricky, JJ(John Wiley and Sons, 1970), pp 73 ff).

Representative methods for the preparation of compounds of formula (2) are shown in Scheme 2 below. Some of these transformations and/or analogous methods are described in the chemical literature e.g. D.J Dixon, S.V Ley and D.A. Longbottom, J. Chem. Soc. Perkin 1; 2231-2232 (1999) ; J. Zhong, X. Gan, K.R. Alliston, Z. Lai, H. Yu, C.S. Groutas, T. Wong and W.C. Groutas, J. Combinatorial Chem. 6, 556-563 (2004).

Scheme 2

(4) (5) (6)

(7) (9) wherein R¹ and R² are as defined above. P¹ represents a suitable carboxylate protecting group such as C _-6 alkyl. P² represents a suitable protecting group such as ie f/ary-butyloxycarbonyl (BOC). L¹ represents a suitable leaving group such as halogen (e.g. bromine, iodine).

Step (i) typically comprises treatment of compound (4) with a chlorosulfonyl carbamate derivative (for example prepared from tertiary butanol and chlorosulfonyl isocyanate) with a suitable base such as triethylamine in a suitable solvent such as dichloromethane at a suitable temperature such as between 0°C and room temperature.

Step (ii) typically comprises intramolecular cyclisation of compound (5) with an azodicarboxylate such as diisopropyl azodicarboxylate and a phosphine such as triphenylphosphine in a suitable solvent such as tetrahydrofuran at a suitable temperature such as room temperature.

Step (iii) typically comprises treatment of compound (6) with a suitable acid such as trifluoroacetic acid in a suitable solvent such as dichloromethane at a suitable temperature such as room temperature.

Step (iv) typically comprises treatment of compound (7) with a suitable base such as sodium hydride and an alkylating agent (8) such as an alkyl halide (e.g. methyl iodide) at a suitable temperature such as between -10°C and 10°C in a suitable solvent such as Λ/,/V-dimethylformamide. Step (v) typically comprises standard deprotection of carboxylic ester (9) to the corresponding carboxylic acid (2) by treatment with a suitable base such as lithium hydroxide in a suitable solvent such as aqueous tetrahydrofuran at a suitable temperature such as 0°C.

Compounds of the general formulae (3), (4) and (8) are typically either available from commercial sources or can be prepared by a person skilled in the art using methods described in the chemical literature (or using analogous methods). Where relevant, pharmaceutically acceptable salts may be prepared conventionally by reaction with the appropriate acid or acid derivative.

Clinical Indications

It is believed that as compounds of the present invention modulate P2X7 receptor function and are capable of antagonizing the effects of ATP at the P2X7 receptor they may be useful in the treatment of pain, including acute pain, chronic pain, chronic articular pain, musculoskeletal pain, neuropathic pain, inflammatory pain, visceral pain, pain associated with cancer, pain associated with migraine, tension headache and cluster headaches, pain associated with functional bowel disorders, lower back and neck pain, pain associated with sprains and strains, sympathetically maintained pain; myositis, pain associated with influenza or other viral infections such as the common cold, pain associated with rheumatic fever, pain associated with myocardial ischemia, post operative pain, cancer chemotherapy, headache, toothache and dysmenorrhea.

Chronic articular pain conditions include rheumatoid arthritis, osteoarthritis, rheumatoid spondylitis, gouty arthritis and juvenile arthritis.

Pain associated with functional bowel disorders includes non-ulcer dyspepsia, non- cardiac chest pain and irritable bowel syndrome.

Neuropathic pain syndromes include: diabetic neuropathy, sciatica, non-specific lower back pain, trigeminal neuralgia, multiple sclerosis pain, fibromyalgia, HIV- related neuropathy, post-herpetic neuralgia, trigeminal neuralgia, and pain resulting from physical trauma, amputation, phantom limb syndrome, spinal surgery, cancer, toxins or chronic inflammatory conditions. In addition, neuropathic pain conditions include pain associated with normally non-painful sensations such as "pins and needles" (paraesthesias and dysesthesias), increased sensitivity to touch

(hyperesthesia), painful sensation following innocuous stimulation (dynamic, static, thermal or cold allodynia), increased sensitivity to noxious stimuli (thermal, cold, mechanical hyperalgesia), continuing pain sensation after removal of the stimulation (hyperpathia) or an absence of or deficit in selective sensory pathways (hypoalgesia).

Other conditions which could potentially be treated by compounds of the present invention include fever, inflammation, immunological diseases, abnormal platelet function diseases (e.g. occlusive vascular diseases), impotence or erectile

dysfunction; bone disease characterised by abnormal bone metabolism or resorbtion; hemodynamic side effects of non-steroidal anti-inflammatory drugs (NSAID's) and cyclooxygenase-2 (COX-2) inhibitors, cardiovascular diseases; neurodegenerative diseases and neurodegeneration, neurodegeneration following trauma, tinnitus, dependence on a dependence-inducing agent such as opiods (e.g. morphine), CNS depressants (e.g. ethanol), psychostimulants (e.g. cocaine) and nicotine;

complications of Type I diabetes, kidney dysfunction, liver dysfunction (e.g. hepatitis, cirrhosis), gastrointestinal dysfunction (e.g. diarrhoea), colon cancer, overactive bladder and urge incontinence. Depression and alcoholism could potentially also be treated by compounds of the present invention.

Inflammation and the inflammatory conditions associated with said inflammation include skin conditions (e.g. sunburn, burns, eczema, dermatitis, allergic dermatitis, psoriasis), meningitis, ophthalmic diseases such as glaucoma, retinitis, retinopathies, uveitis and of acute injury to the eye tissue (e.g. conjunctivitis), inflammatory lung disorders (e.g. asthma, bronchitis, emphysema, allergic rhinitis, respiratory distress syndrome, pigeon fancier's disease, farmer's lung, chronic obstructive pulmonary disease (COPD), airways hyperresponsiveness); gastrointestinal tract disorders (e.g. aphthous ulcer, Crohn's disease, atopic gastritis, gastritis varialoforme, ulcerative colitis, coeliac disease, regional ileitis, irritable bowel syndrome, inflammatory bowel disease, gastrointestinal reflux disease); organ transplantation and other conditions with an inflammatory component such as vascular disease, migraine, periarteritis nodosa, thyroiditis, aplastic anaemia, Hodgkin's disease, sclerodoma, myaesthenia gravis, multiple sclerosis, sorcoidosis, nephrotic syndrome, Bechet's syndrome, gingivitis, myocardial ischemia, pyrexia, systemic lupus erythematosus, polymyositis, tendinitis, bursitis, and Sjogren's syndrome. Immunological diseases include autoimmune diseases, immunological deficiency diseases or organ transplantation. Bone diseases characterised by abnormal bone metabolism or resorbtion include osteoporosis (especially postmenopausal osteoporosis), hyper-calcemia,

hyperparathyroidism, Paget's bone diseases, osteolysis, hypercalcemia of malignancy with or without bone metastases, rheumatoid arthritis, periodontitis, osteoarthritis, ostealgia, osteopenia, cancer cacchexia, calculosis, lithiasis (especially urolithiasis), solid carcinoma, gout and ankylosing spondylitis, tendinitis and bursitis.

Cardiovascular diseases include hypertension or myocardiac ischemia;

atherosclerosis; functional or organic venous insufficiency; varicose therapy;

haemorrhoids; and shock states associated with a marked drop in arterial pressure (e.g. septic shock).

Neurodegenerative diseases include dementia, particularly degenerative dementia (including senile dementia, dementia with Lewy bodies, Alzheimer's disease, Pick's disease, Huntingdon's chorea, Parkinson's disease and Creutzfeldt-Jakob disease, Amyotrophic Lateral Sclerosis (ALS) and motor neuron disease); vascular dementia (including multi-infarct dementia); as well as dementia associated with intracranial space occupying lesions; trauma; infections and related conditions (including HIV infection, meningitis and shingles); metabolism; toxins; anoxia and vitamin deficiency; and mild cognitive impairment associated with ageing, particularly Age Associated Memory Impairment.

In one embodiment, the compound of the invention are useful in the treatment of degenerative dementia, including senile dementia, dementia with Lewy bodies, Alzheimer's disease, Pick's disease, Huntingdon's chorea, Parkinson's disease and Creutzfeldt-Jakob disease, Amyotrophic Lateral Sclerosis (ALS) or motor neuron disease; vascular dementia including multi-infarct dementia; or mild cognitive impairment (MCI) including MCI associated with ageing such as age associated memory impairment. The compounds of formula (I) may also be useful for neuroprotection and in the treatment of neurodegeneration following trauma such as stroke, cardiac arrest, pulmonary bypass, traumatic brain injury, spinal cord injury or the like. The compounds of the present invention may also be useful in the treatment of malignant cell growth and/or metastasis, and myoblastic leukaemia. Complications of Type 1 diabetes include diabetic microangiopathy, diabetic retinopathy, diabetic nephropathy, macular degeneration, glaucoma, nephrotic syndrome, aplastic anaemia, uveitis, Kawasaki disease and sarcoidosis.

Kidney dysfunction includes nephritis, glomerulonephritis, particularly mesangial proliferative glomerulonephritis and nephritic syndrome.

It is to be understood that reference to treatment includes both treatment of established symptoms and prophylactic treatment, unless explicitly stated otherwise. According to a further aspect of the invention, we therefore provide a compound of formula (I) or a pharmaceutically acceptable salt thereof for use in human or veterinary medicine.

According to another aspect of the invention, we provide a compound of formula (I) or a pharmaceutically acceptable salt thereof for use in the treatment of a condition which is mediated by P2X7 receptors.

According to a further aspect of the invention, we provide a method of treating a human or animal subject suffering from a condition which is mediated by P2X7 receptors which comprises administering to said subject an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.

According to a further aspect of the invention we provide a method of treating a human or animal subject suffering from pain, inflammation or a neurodegenerative disease, which method comprises administering to said subject an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.

According to a yet further aspect of the invention we provide a method of treating a human or animal subject suffering from inflammatory pain, neuropathic pain or visceral pain which method comprises administering to said subject an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof. According to a further aspect of the invention we provide a method of treating a subject, for example a human subject, suffering from Alzheimer's disease which method comprises administering to said subject an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.

According to another aspect of the invention, we provide the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment of a condition which is mediated by the action of P2X7 receptors.

According to another aspect of the invention we provide the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment or prevention of pain, inflammation or a

neurodegenerative disease.

According to another aspect of the invention we provide the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment or prevention of inflammatory pain, neuropathic pain or visceral pain.

In one aspect of the invention we provide the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment or prevention of Alzheimer's disease. In order to use a compound of formula (I) or a pharmaceutically acceptable salt thereof for the treatment of humans and other mammals it is normally formulated in accordance with standard pharmaceutical practice as a pharmaceutical composition. Therefore in another aspect of the invention there is provided a pharmaceutical composition comprising a compound of formula (I), or a pharmaceutically acceptable salt thereof, adapted for use in human or veterinary medicine.

In order to use the compounds of formula (I) in therapy, they will normally be formulated into a pharmaceutical composition in accordance with standard pharmaceutical practice. The present invention also provides a pharmaceutical composition, which comprises a compound of formula (I), or a pharmaceutically acceptable salt thereof, and optionally a pharmaceutically acceptable carrier. Compounds of formula (I) may be used in combination with other therapeutic agents, for example medicaments claimed to be useful in the treatment of the above mentioned disorders. Suitable examples of other such therapeutic agents may include a 32-agonist (also known as β2 adrenoceptor agonists; e.g. formoterol) and/or a corticosteroid (e.g. budesonide, fluticasone (e.g. as propionate or furoate esters), mometasone (e.g. as furoate), beclomethasone (e.g. as 17-propionate or 17,21 -dipropionate esters), ciclesonide, triamcinolone (e.g. as acetonide), flunisolide, rofleponide and butixocort (e.g. as propionate ester), for the treatment of respiratory disorders (such as asthma and chronic obstructive pulmonary disease (COPD)) as described in WO

2007/008155 and WO 2007/008157.

A further therapeutic agent may include a 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitor (e.g. atorvastatin, fluvastatin, lovastatin, pravastatin, rosuvastatin, and simvastatin) for the treatment of cardiovascular disorders (such as atherosclerosis) as described in WO 2006/083214.

A further therapeutic agent may include a non-steroid anti-inflammatory drug (NSAID; e.g. ibuprofen, naproxen, aspirin, celecoxib, diclofenac, etodolac, fenoprofen, indomethacin, ketoprofen, ketoralac, oxaprozin, nabumetone, sulindac, tolmetin, rofecoxib, valdecoxib, lumaricoxib, meloxicam, etoricoxiband and parecoxib) for the treatment of an inflammatory disease or disorder (such as rheumatoid arthritis or osteoarthritis) as described in WO 2005/025571.

A further therapeutic agent may include a tumour necrosis factor a (TNFa) inhibitor (e.g. Etanercept or an anti- TNFa antibody such as Infliximab and Adalimumab) for the treatment of an inflammatory disease or disorder (such as rheumatoid arthritis or osteoarthritis) as described in WO 2004/105798.

A further therapeutic agent may include 2-hydroxy-5- [ [4- [ (2- pyridinylamino) sulfonyl] phenyl] azo] benzoic acid (sulfasalazine) for the treatment of an

inflammatory disease or disorder (such as rheumatoid arthritis) as described in WO 2004/105797.

A further therapeutic agent may include N-[4-[[(2, 4-diamino-6-pteridinyl) methyl] methylamino] benzoyl]- L-glutamic acid (methotrexate) for the treatment of an inflammatory disease or disorder (such as rheumatoid arthritis) as described in WO 2004/105796.

A further therapeutic agent may include an inhibitor of pro TNFa convertase enzyme (TACE) for the treatment of an inflammatory disease or disorder (such as rheumatoid arthritis) as described in WO 2004/073704.

A further therapeutic agent may include:

a) sulfasalazine;

b) a statin, such as atorvastatin, lovastatin, pravastatin, simvastatin, fluvastatin, cerivastatin, crilvastatin, dalvastatin, rosuvastatin, tenivastatin, fluindostatin, velostatin, dalvastatin, nisvastatin, bervastatin, pitavastatin, rivastatin, glenvastatin, eptastatin, tenivastatin, flurastatin, rosuvastatin or itavastatin;

c) a glucocorticoid agent, such as dexamethasone, methylprednisolone,

prednisolone, prednisone and hydrocortisone;

d) an inhibitor of p38 kinase;

e) an anti-IL-6-receptor antibody;

f) anakinra;

g) an anti-IL-1 monoclonal antibody;

h) an inhibitor of JAK3 protein tyrosine kinase;

i) an anti-macrophage colony stimulation factor (M-CSF) monoclonal antibody; or j) an anti-CD20 monoclonal antibody, such as rituximab, PRO70769, HuMax-CD20 (Genmab AJS), AME-133 (Applied Molecular Evolution), or hA20 (Immunomedics, Inc.)

for the treatment of an IL-1 mediated disease (such as rheumatoid arthritis) as described in WO 2006/003517.

When the compounds are used in combination with other therapeutic agents, the compounds may be administered either sequentially or simultaneously by any convenient route.

The invention thus provides, in a further aspect, a combination comprising a compound of formula (I) or a pharmaceutically acceptable derivative thereof together with a further therapeutic agent or agents.

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 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.

When a compound of formula (I) or a pharmaceutically acceptable derivative thereof is used in combination with a second therapeutic agent active against the same disease state the dose of each compound may differ from that when the compound is used alone. Appropriate doses will be readily appreciated by those skilled in the art.

A pharmaceutical composition of the invention, which may be prepared by admixture, suitably at ambient temperature and atmospheric pressure, is usually adapted for oral, parenteral or rectal administration and, as such, may be in the form of tablets, capsules, oral liquid preparations, powders, granules, lozenges, reconstitutable powders, injectable or infusable solutions or suspensions or suppositories. Orally administrable compositions are generally preferred.

Tablets and capsules for oral administration may be in unit dose form, and may contain conventional excipients, such as binding agents, fillers, tabletting lubricants, disintegrants and acceptable wetting agents. The tablets may be coated according to methods well known in normal pharmaceutical practice.

Oral liquid preparations may be in the form of, for example, aqueous or oily suspension, solutions, emulsions, syrups or elixirs, or may be in the form of a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils), preservatives, and, if desired, conventional flavourings or colourants. For parenteral administration, fluid unit dosage forms are prepared utilising a compound of the invention or pharmaceutically acceptable salt thereof and a sterile vehicle. The compound, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions, the compound can be dissolved for injection and filter sterilised before filling into a suitable vial or ampoule and sealing. Advantageously, adjuvants such as a local anaesthetic, preservatives and buffering agents are dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. Parenteral suspensions are prepared in substantially the same manner, except that the compound is suspended in the vehicle instead of being dissolved, and sterilization cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspension in a sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound.

The composition may contain from 0.1 % to 99% by weight, preferably from 10 to 60% by weight, of the active material, depending on the method of administration.

The dose of the compound used in the treatment of the aforementioned disorders will vary in the usual way with the seriousness of the disorders, the weight of the sufferer, and other similar factors. However, as a general guide suitable unit doses may be 0.05 to 1000 mg, more suitably 0.05 to 200 mg; and such unit doses can for example be administered once a day, although administration more than once (e.g. twice) a day may be used. Such therapy may extend for a number of weeks or months.

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 herein as though fully set forth.

The following Descriptions and Examples illustrate the preparation of compounds of the invention but are not intended to be limiting.

Examples:

The general methods (a)-(c), along with the synthetic methods outlined in Schemes 1 and 2 above, for the preparation of compounds or salts of the present invention are further illustrated by the following examples.

Example 1 /V-{[2-Chloro-3-(trifluoromethyl)phenyl]methyl}-2,5-dimethyl-1 ,2,5- thiadiazolidine-3-carboxamide 1 ,1-dioxide (in a form obtainable or prepared from N- methyl-L-serine) (E1)

A mixture of 2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxylic acid 1 ,1 -dioxide (136 mg, 0.700 mmol, prepared as described below), N-ethyl morpholine (0.268 ml, 2.100 mmol), 1-hydroxybenzotriazole hydrate (129 mg, 0.84 mmol) and 1 -ethyl-3-(3- dimethylaminopropyl)carbodiimide hydrochloride (161 mg, 0.840 mmol) in dichloromethane (9 ml) was stirred at room temperature for 10 minutes. A solution of {[2-chloro-3-(trifluoromethyl)phenyl]methyl}amine (147 mg, 0.700 mmol) in dichloromethane (1 ml) was added and the reaction stirred at room temperature for 3 hours. The reaction mixture was diluted with dichloromethane (10 ml) and the solution was washed with saturated sodium hydrogen carbonate solution (10 ml), water (10 ml), citric acid solution (10 ml) and brine (10 ml), dried and evaporated. The residue was purified by mass-directed automated HPLC. The residue was triturated with ether/isohexane and the solvent was evaporated. The residue was dried under high vacuum at room temperature using phosphorus pentoxide as drying agent to give N-{[2-chloro-3-(trifluoromethyl)phenyl]methyl}-2,5-dimethyl-1 ,2,5- thiadiazolidine-3-carboxamide 1 ,1 -dioxide (120 mg, 44%).

LC/MS [M+H]⁺ = 386, retention time = 2.66 minutes. The 2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxylic acid 1 ,1 -dioxide used in the above procedure was prepared as follows:

(i) Acetyl chloride (14.22 ml, 200 mmol) was cautiously added to a solution of methanol (80 ml). After stirring at room temperature for 10 minutes, N-methyl-L- serine (2.382 g, 20 mmol) was added and the reaction mixture was heated at reflux for 18 hours. After cooling to room temperature the solvent was evaporated. The residue was triturated with ether and the resulting solid was collected and dried (over

P₂0₅) to give methyl N-methyl-L-serinate hydrochloride (3.8 g). LC/MS [M+H]⁺ =

134.

(ii) A solution of tert-butanol (3.25 ml, 34.0 mmol) in dichloromethane (30 ml) was added dropwise to a stirred solution of chlorosulfonyl isocyanate (2.95 ml, 34.0 mmol) in dichloromethane (60 ml) at 0°C. After 15 minutes at 0°C the solution was added dropwise to a stirred suspension of methyl N-methyl-L-serinate hydrochloride (5.77 g, 34 mmol) and triethylamine (9.48 ml, 68.0 mmol) in dichloromethane (90 ml) at 0°C. The cooling bath was removed and the reaction mixture was stirred at room temperature for 1 hour. The reaction mixture was washed with water (100 ml), 2N hydrochloric acid (100 ml), water (100 ml), saturated sodium hydrogen carbonate solution (100 ml), water (100 ml) and brine (100 ml), dried and evaporated. The residue was purified by silica gel chromatography eluting with 20-100% ethyl acetate in isohexane to give methyl N-[({[(1 ,1 -dimethylethyl)oxy]carbonyl}amino)sulfonyl]-N- methyl-L-serinate (3.8 g, 36%), LC/MS [M-H]- = 31 1.

(iii) A solution of methyl N-[({[(1 ,1-dimethylethyl)oxy]carbonyl}amino)sulfonyl]-N- methyl-L-serinate (3.748 g, 12.00 mmol) in tetrahydrofuran (60 ml) was treated with triphenylphosphine (6.29 g, 24.00 mmol) and diisopropyl azodicarboxylate (4.67 ml, 24.00 mmol) and the reaction mixture was stirred at room temperature for 18 hours. The solvent was evaporated and the residue was purified by silica gel

chromatography eluting with 0-5% methanol in dichloromethane to give crude 2-(1 ,1- dimethylethyl) 4-methyl-5-methyl-1 ,2,5-thiadiazolidine-2,4-dicarboxylate 1 ,1 -dioxide

(3 g). LC/MS [M+Na]⁺ = 317.

(iv) A solution of 2-(1 ,1 -dimethylethyl) 4-methyl 5-methyl-1 ,2,5-thiadiazolidine-2,4- dicarboxylate 1 ,1 -dioxide (2.94 g, 10 mmol) in TFA/DCM (1 :2, 30 ml) was stirred at room temperature for 2 hours. The solution was evaporated. The residue was partitioned between ethyl acetate (40 ml) and saturated sodium hydrogen carbonate solution (40 ml). The organic phase was separated, washed with brine (40 ml), dried and evaporated. The residue was purified by silica gel chromatography eluting with 20-100% ethyl acetate in isohexane to give methyl 2-methyl-1 ,2,5-thiadiazolidine-3- carboxylate 1 ,1 -dioxide (1.05 g, 54%). LC/MS [M+H]⁺ = 195.

(v) A stirred solution of methyl 2-methyl-1 ,2,5-thiadiazolidine-3-carboxylate 1 ,1- dioxide (971 mg, 5.00 mmol) in N,N-dimethylformamide (10 ml) was cooled to -10°C under argon and treated with iodomethane (1.251 ml, 20.00 mmol). Sodium hydride (60% dispersion in oil) (200 mg, 5 mmol) was added in portions over 5 minutes. The mixture was stirred at -10°C to 0°C for 2 hours and then stirred at 10°C for 1 hour. The solvent was evaporated and the residue was partitioned between ethyl acetate (30 ml) and brine (20 ml). The aqueous layer was re-extracted with ethyl acetate (2 x 20 ml) and the organic extracts were combined, washed with brine (20 ml), dried and evaporated. The residue was purified by silica gel chromatography eluting with 10- 100% ethyl acetate in isohexane to give methyl 2,5-dimethyl-1 ,2,5-thiadiazolidine-3- carboxylate 1 ,1 -dioxide (974 mg, 94% ) LC/MS [M+H]⁺ = 209. (vi) A stirred solution of methyl 2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxylate 1 ,1 - dioxide (0.833 g, 4 mmol) in a mixture of tetrahydrofuran (10 ml) and water (6 ml) at

0°C was treated with lithium hydroxide (0.287 g, 12.00 mmol). The solution was stirred at 0°C for 3 hours. The solution was acidified to pH 3 with 2N hydrochloric acid and the solvent was evaporated. The residue was partitioned between ethyl acetate (30 ml) and water (10 ml). The organic phase was separated and the aqueous layer was extracted with ethyl acetate (3 x 20 ml). The organic extracts were combined, dried and evaporated to give 2,5-dimethyl-1 ,2,5-thiadiazolidine-3- carboxylic acid 1 ,1 -dioxide (777 mg, 100%), which was used crude in the next reaction. LC/MS [M+H]⁺ = 195.

Example 2 /V-[(2,4-Dichlorophenyl)methyl]-2,5-dimethyl-1 ,2,5-thiadiazolidine-3- carboxamide 1 ,1-dioxide (in a form obtainable or prepared from N-methyl-L-serine)

(E2)

/V-[(2,4-Dichlorophenyl)methyl]-2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxamide 1 ,1- dioxide was prepared in an analogous manner to that described for /V-{[2-Chloro-3- (trifluoromethyl)phenyl]methyl}-2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxamide 1 ,1- dioxide (E1 ) above but using [1 -(2,4-dichlorophenyl)methyl]amine in the place of {[2- chloro-3-(trifluoromethyl)phenyl]methyl}amine. LC/MS [M+H]⁺ = 352, retention time = 2.59 minutes.

Mass-directed automated HPLC

Where applicable, purification by mass-directed automated HPLC was carried out using the following apparatus and conditions: Hardware

Waters 2525 Binary Gradient Module

Waters 515 Makeup Pump

Waters Pump Control Module Waters 2767 Inject Collect

Waters Column Fluidics Manager

Waters 2996 Photodiode Array Detector

Waters ZQ Mass Spectrometer

Gilson 202 fraction collector

Gilson Aspec waste collector

Software

Waters MassLynx version 4 SP2

Column

The columns used are Waters Atlantis, the dimensions of which are 19mm x 100mm (small scale) and 30mm x 100mm (large scale). The stationary phase particle size is 5μη-ι.

Solvents

A : Aqueous solvent = Water + 0.1 % Formic Acid

B : Organic solvent = Acetonitrile + 0.1 % Formic Acid

Make up solvent = Methanol : Water 80:20

Needle rinse solvent = Methanol

Methods

There are five methods used depending on the analytical retention time of the compound of interest. They have a 13.5-minute runtime, which comprises a 10- minute gradient followed by a 3.5 minute column flush and re-equilibration step.

Large/Small Scale 1 .0-1 .5 = 5-30% B

Large/Small Scale 1 .5-2.2 = 15-55% B

Large/Small Scale 2.2-2.9 = 30-85% B

Large/Small Scale 2.9-3.6 = 50-99% B

Large/Small Scale 3.6-5.0 = 80-99% B (in 6 minutes followed by 7.5 minutes flush and re-equilibration)

Flow rate

All of the above methods have a flow rate of either 20mls/min (Small Scale) or 40mls/min (Large Scale). Liquid Chromatography / Mass Spectrometry

Analysis of the above Examples by Liquid Chromatography / Mass Spectrometry (LC/MS) was carried out using the apparatus and conditions indicated in the methods shown below :

Liquid Chromatography:

Hardware

Agilent 1 100 Gradient Pump

Agilent 1 100 Autosampler

Agilent 1 100 DAD Detector

Agilent 1 100 Degasser

Agilent 1 100 Oven

Agilent 1 100 Controller

Waters ZQ Mass Spectrometer

Sedere Sedex 85

Software

Waters MassLynx version 4.0 SP2 Column

The column used is a Waters Atlantis, the dimensions of which are 4.6mm x 50mm. The stationary phase particle size is 3μη-ι.

Solvents

A : Aqueous solvent = Water + 0.05% Formic Acid

B : Organic solvent = Acetonitrile + 0.05% Formic Acid The generic method used has a 5 minute runtime.

The above method has a flow rate of 3ml/mins. The injection volume for the generic method is 5ul. The column temperature is 30deg.

The UV detection range is from 220 to 330nm.

Pharmacological data

Compounds of the invention may be tested for in vitro biological activity at the P2X7 receptor in accordance with the following studies: Ethidium Accumulation Assay

Studies were performed using NaCI assay buffer of the following composition (in mM): 140mM NaCI, HEPES (4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid) 10, /V-methyl-D-glucamine 5, KCI 5.6, D-glucose 10, CaCI₂ 0.5 (pH 7.4). Human

Embryonic Kidney (HEK) 293 cells, expressing human recombinant P2X7 receptors, were grown in poly-D-lysine pretreated 96 well plates for 18-24 h. (The cloning of the human P2X7 receptor is described in US 6,133,434). The cells were washed twice with 350μΙ of assay buffer before addition of 50μΙ of antagonist. The cells were then incubated at room temperature (19-21 °C) for 30 min before addition of ATP and ethidium (100μΜ final assay concentration). The ATP concentration was chosen to be close to the EC₈o for the receptor type and was 1 mM for studies on the human P2X7 receptor. Incubations were continued for 8 or 16 min and were terminated by addition of 25μΙ of 1 .3M sucrose containing 4mM of the P2X7 receptor antagonist reactive black 5 (Aldrich). Cellular accumulation of ethidium was determined by measuring fluorescence (excitation wavelength of 530nm and emission wavelength of 620nm) from below the plate with a Canberra Packard Fluorocount (14 Station Road Pangbourne, Reading, Berkshire RG8 7AN, UK) or a FlexStation II 384 from Molecular Molecular Devices (660-665 Eskdale Road, Wokingham, Berkshire RG41 5TS, UK). Antagonist plC₅₀ values for blocking ATP responses were determined using iterative curve fitting techniques.

Fluorescent Imaging Plate Reader (FLIPR) Ca Assay

Studies were performed using NaCI assay buffer of the following composition (in mM) for human P2X7: 137 NaCI; 20 HEPES (4-(2-hydroxyethyl)-1 - piperazine-1- ethanesulfonic acid); 5.37 KCI; 4.17 NaHC0₃; 1 CaCI₂; 0.5 MgS0₄; and 1 g/L of D- glucose (pH 7.4).

Human Embryonic Kidney (HEK) 293 cells, stably expressing human recombinant P2X7 receptors, were grown in poly-D-lysine pre-treated 384 well plates for 24-48h. Alternatively human osteosarcoma (U-20S) cells transduced with modified

Baculovirus (BacMam) vector to deliver the gene coding for human P2X7 receptor (i.e. transiently expressing human P2X7 receptors) were grown in substantially the same conditions as described above for the HEK293 cells. (The cloning of the human P2X7 receptor is described in US 6,133,434). The cells were washed three times with 80μΙ of assay buffer, loaded for 1 h at 37°C with 2μΜ Fluo4-AM (4-(6- Acetoxymethoxy-2,7-difluoro-3-oxo-9-xanthenyl)-4'-methyl-2,2'- (ethylenedioxy)dianiline-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl) ester), a Ca²⁺-sensitive, cell-permeable, fluorescence dye (Tef Labs. Inc., 9415 Capitol View Drive, Austin, TX 78747 USA), washed three times again, and left with 30μΙ buffer before the addition of 10 μΙ of 4x concentrated antagonist. The cells were then incubated at room temperature for 30 mins before addition (online, by FLIPR384 or FLIPR3 instrument (Molecular Devices, 131 1 Orleans Drive, Sunnyvale, CA 94089- 1 136, USA)) of Benzoylbenzoyl-ATP (BzATP) 60μΜ final assay concentration. The BzATP concentration was chosen to be close to the EC₈o for the receptor type.

Incubations and reading were continued for 90sec, and intracellular calcium increase was determined by measuring fluorescence (excitation wavelength of 488nm and emission wavelength of 516nm) from below the plate, with FLIPR charged-coupled device (CCD) camera. Antagonist plC₅₀ values for blocking BzATP responses were determined using iterative curve fitting techniques.

The compounds of Examples 1 and 2 were tested in the FLIPR Ca Assay and/or the Ethidium Accumulation Assay for human P2X7 receptor antagonist activity and found to have plC50 values within the range of ca. 6.6 to ca. 7.0 in the FLIPR Ca Assay (using either HEK293 or U-20S cells; n = 1 ); and had plC50 values within the range of ca. 7.5 to ca. 7.9 in the Ethidium Accumulation Assay (as average values, n=3).

Claims

1. A compound of formula (I) or a pharmaceutically acceptable salt thereof

(I)

wherein:

R¹ is C-|_3alkyl or C-|fluoroalkyl-CH2-;

R2 is hydrogen, C-|_4alkyl, C-|fluoroalkyl-CH2-, C3_gcycloalkyl,

C3_gcycloalkyl-methyl-, optionally substituted benzyl, or optionally substituted heteroaryl-(CH2)_n-,

wherein n is 0 or 1 ,

wherein in R2 the benzyl is optionally substituted on the ring with one or two substituents independently being methyl, methoxy, fluorine or chlorine, and wherein in R2 the heteroaryl-(CH2)_n- is optionally substituted on the heteroaryl ring with one or two substituents independently being C<|_3alkyl, CF3, methoxy, a halogen atom, or cyano; and wherein:

R3, R4_; 5_j R6 _ANC| R7 independently are hydrogen, a halogen atom, C-_|_4alkyl, trifluoromethyl, or cyano,

such that one or both of R^ and R^ is or are a group other than hydrogen.

2. A compound or salt as claimed in claim 1 , wherein is methyl or ethyl.

3. A compound or salt as claimed in claim 1 or 2, wherein R^ is hydrogen, C<|_3alkyl, C-|fluoroalkyl-CH2-, C3_gcycloalkyl, C3_gcycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-. wherein n is 0 or 1 , and wherein the heteroaryl is pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl.

4. A compound or salt as claimed in claim 3, wherein is hydrogen, C-|_3alkyl, C3_4cycloalkyl-methyl-, or optionally substituted heteroaryl-(CH2)_n-,

wherein n is 0 or 1 ,

wherein the heteroaryl is pyridinyl, pyrimidinyl, imidazolyl or pyrazolyl, optionally substituted on the heteroaryl ring with one or two substituents independently being methyl, CF3, methoxy, fluorine, chlorine, or cyano.

5. A compound or salt as claimed in claim 4, wherein R2 is hydrogen, C-_|_3alkyl, or optionally substituted heteroaryl,

and wherein the heteroaryl is pyridinyl or pyrimidinyl, optionally substituted on the heteroaryl ring with one substituent independently being methyl, CF3, methoxy, fluorine or chlorine.

6. A compound or salt as claimed in claim 5, wherein R2 is hydrogen, methyl or ethyl.

7. A compound or salt as claimed in any one of the preceding claims, wherein R3, R4_; 5_j R6 _ANC| R7 independently are hydrogen, chlorine, fluorine, methyl or trifluoromethyl,

such that one or both of R^ and R^ is or are a group other than hydrogen.

8. A compound or salt as claimed in claim 7, wherein

R3 and R^ both are hydrogen,

R5 is hydrogen, chlorine or fluorine,

R6 is hydrogen, chlorine, fluorine or trifluoromethyl, and

R7 is chlorine, fluorine, methyl or trifluoromethyl.

9. A compound or salt as claimed in claim 8, wherein

R3 and R^ both are hydrogen,

R7 is chlorine or methyl, and

either R^ is hydrogen, and R^ is trifluoromethyl,

or R5 is chlorine, and R^ is hydrogen,

or R5 is fluorine, and R^ is hydrogen or fluorine.

10. A compound or salt as claimed in claim 7, wherein

R3 is hydrogen, chlorine, fluorine or methyl,

R4 is hydrogen,

R5 is chlorine or fluorine,

is hydrogen, and

R^ is chlorine or methyl.

11. A compound or salt as claimed in any one of the preceding claims, wherein: R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R7 is chlorine;

R3, R4 and R^ each are hydrogen and R^ and R^ both are chlorine;

R3 and R4 both are hydrogen, R^ and R^ both are fluorine, and R7 is chlorine;

R3, R^ and R^ each are hydrogen, R^ is trifluoromethyl, and R^ is methyl;

R3 and R4 both are hydrogen, R^ is fluorine, R^ is trifluoromethyl, and R^ is chlorine;

R3 is methyl, R4 and R6 both are hydrogen, and R^ and R^ both are chlorine;

R3, R5 and R^ each are chlorine, and R4 and R^ both are hydrogen;

R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R7 is fluorine;

R3, R4 and R^ each are hydrogen, R^ is fluorine, and R^ is chlorine;

R3, R4 and R6 each are hydrogen, R^ is chlorine, and R^ is methyl;

R3, R4 and R^ each are hydrogen, R^ is chlorine, and R^ is methyl;

R3 and R4 both are hydrogen, R^ is fluorine, and R^ and R7 both are chlorine;

R3, R4 and R^ each are hydrogen and R^ and R^ both are chlorine; or

R3 is fluorine, R4 and R6 both are hydrogen, and R^ and R^ both are chlorine.

12. A compound or salt as claimed in claim 1 1 , wherein:

R3, R4 and R^ each are hydrogen, R6 is trifluoromethyl, and R7 is chlorine;

R3, R4 and R^ each are hydrogen and R^ and R^ both are chlorine; or

R3 and R4 both are hydrogen, R^ and R^ both are fluorine, and R7 is chlorine,

13. A compound of formula (IA) or a pharmaceutically acceptable salt thereof:

(IA)

wherein:

R1 , R2, R3_j 4_; R5_j R6_{j anc}| R7 _{are as} defined in any one of the preceding claims for the compound of formula (I) or the salt thereof,

and wherein more than 50% by molarity of the compound of formula (IA) or the pharmaceutically acceptable salt thereof has the stereochemistry shown at the thiadiazolidine ring-carbon atom which is directly bonded to the R¹-bearing ring- nitrogen atom.

14. A compound which is:

(i) /V-{[2-chloro-3-(trifluoromethyl)phenyl]methyl}-2,5-dimethyl-1 ,2,5-thiadiazolidine-3- carboxamide 1 ,1-dioxide

(ii) /V-[(2,4-dichlorophenyl)methyl]-2,5-dimethyl-1 ,2,5-thiadiazolidine-3-carboxamide 1 ,1-dioxide

or a pharmaceutically acceptable salt thereof.

15. A pharmaceutical composition which comprises a compound of formula (I) or a pharmaceutically acceptable salt thereof, as defined in any one of claims 1 to 14, and a pharmaceutically acceptable carrier.

16. A pharmaceutical composition as claimed in claim 15 for use in the treatment of pain, inflammation or a neurodegenerative disease.

17. A compound or salt as claimed in any one of claims 1 to 14, for use in therapy.

18. A compound or salt as claimed in claim 17 for use in the treatment of pain, inflammation or a neurodegenerative disease.

19. A method of treating a human or animal subject suffering from pain, inflammation or a neurodegenerative disease, which method comprises

administering to said subject an effective amount of a compound or a

pharmaceutically acceptable salt thereof as defined in any one of claims 1 to 14.

20. Use of a compound or a pharmaceutically acceptable salt thereof, as defined in any one of claims 1 to 14, for the manufacture of a medicament for the treatment of pain, inflammation or a neurodegenerative disease.

2 . The pharmaceutical composition of claim 6, the compound of claim 18, the method of 19 or the use of claim 20 wherein the neurodegenerative diseases is dementia, including: degenerative dementia, such as senile dementia, dementia with Lewy bodies, Alzheimer's disease, Pick's disease, Huntingdon's chorea, Parkinson's disease, Creut2feldt-Jakob disease, Amyotrophic Lateral Sclerosis (ALS) and motor neuron disease; vascular dementia, such as multl-infarct dementia; and dementia associated with intracranial space occupying lesions, trauma, Infections and related conditions, such as HIV infection, meningitis and shingles, metabolism, toxins, anoxia and vitamin deficiency; or mild cognitive impairment (MGI) associated with ageing, such as Age Associated Memory Impairment.