Serine/threonine kinase inhibitors

A compound of formula I wherein:

• R1 is H, C1-3 alkyl, C1-3 fluoroalkyl, oxetan-3-yl or 3-methyl-oxetan-3-yl;
• R2 is (i) C2-6 hydroxyalkyl or C2-6 dihydroxyalkyl,
• (ii) (alkylene)nNRaRb wherein the alkylene chain is optionally substituted by a hydroxyl,
• (iii) (alkylene)1-3OR5 wherein R5 is (alkylene)2-4NRaRb, (alkylene)2-4ORf or a heterocycle selected from azetidine, pyrrolidine, piperidine or azepine said heterocycle optionally substituted by C1-6 alkyl,
• (iv) (alkylene)rC(O)NRaRb,
• (v) (alkylene)n-CN,
• (vi) (alkylene)t-(C4-6-cycloalkyl NRcRd),
• (vii) heterocyclyl-(alkylene)n wherein heterocyclyl refers to substituted azetidinyl, pyrrolidinyl, 4,4-difluoro-pyrrolidin-3-yl, piperidinyl, 3,3-difluoro-piperidin-3-yl, azepinyl, morpholinyl, 4-methylmorpholin-2-yl, 5-amino-1,3-dioxolan-2-yl, 5-methylamino-1,3-dioxolan-2-yl, 3-aza-bicyclo[3.1.0]hexan-6-yl, 5-oxa-2-azaspiro[3.4]octan-7-yl, 1-oxa-8-azaspiro[4.5]decan-3-yl, 1-oxa-7-azaspiro[4.4]nonan-3-yl, 5,9-dioxa-2-azaspiro[3.5]nonan-7-yl, 1,1-dioxo-4-thiazinan-2-yl or piperazinyl said heterocyclyl moiety optionally substituted by C(═O)CHRfNH2, oxo, hydroxyl, amino, C1-3 alkylamino, C1-3 dialkylamino, cyano, oxetan-3-yl or C1-6-hydroxyalkyl, or
• (viii) (alkylene)rS(O)2R5 wherein R5 is (alkylene)0-3NRaRb azetidinyl, pyrrolidinyl or piperidinyl;
• or,
• (ix) 1-imino-1-oxa-thianyl-4-yl or 1,1-dioxidotetrahydro-2H-thiopyran-4-yl;
• Ra and Rb are (a) independently in each occurrence hydrogen, C1-3 alkyl, C2-4 aminoalkyl, C2-4-hydroxyalkyl, pyrrolidinyl, piperidinyl or azetidinyl, or, (b) Ra and Rb together with the nitrogen to which they are attached form a four to seven-membered mono- or bicyclic-ring optionally containing another heteroatom selected from O, NRe or S(O)0-2 which is optionally substituted by one or two hydroxyl or (CH2)0-2N(Rf)2;
• Rc and Rd are independently in each occurrence hydrogen, C1-3 alkyl or oxetanyl;
• Re is hydrogen, C1-3 alkyl or C1-3 alkylsulfonyl;
• Rf is hydrogen or C1-3 alkyl;
• R3 is heteroaryl wherein the heteroaryl ring is pyridin-2-yl, pyrazin-2-yl, thiazol-4-yl, thiazol-2-yl, pyrazol-3-yl, 1,2,4-triazol-2-yl or 1,2,4-oxadiazol-3-yl each optionally substituted by an R4 or a C1-3 hydroxyalkyl moiety;
• R4 is C1-6 alkyl, cyclopropyl or halogen;
• n is 2-6;
• r is 1-6;
• s is 0, 1 or 2;
• t is 0-6;
• or,
• a pharmaceutically acceptable salt thereof, with the proviso that the compound of formula I is not:
• 8-(trans-4-aminocyclohexyl)-6-[2-chloro-4-(6-methyl-2-pyrazinyl)phenyl]-2-(ethylamino)-pyrido[2,3-d]pyrimidin-7(8H)-one,
• 8-(trans-4-aminocyclohexyl)-6-[2-chloro-4-(6-methyl-2-pyrazinyl)phenyl]-2-[(1-methylethyl)amino]-pyrido[2,3-d]pyrimidin-7(8H)-one,
• 6-(2-chloro-4-(5-methyl-1,2,4-oxadiazol-3-yl)phenyl)-2-(ethylamino)-8-(piperidin-4-ylmethyl)pyrido[2,3-d]pyrimidin-7(8H)-one, or,
• 6-(2-chloro-4-(5-methyl-1,2,4-oxadiazol-3-yl)phenyl)-2-(isopropylamino)-8-(piperidin-4-ylmethyl)pyrido[2,3-d]pyrimidin-7(8H)-one.