Pyridopyrimidines derivatives as P2X3 inhibitors

A compound of formula (I)

• wherein X1, X2 and X3 are independently CH or N, wherein at least one of X1, X2, and X3 is N, and wherein X1 is N when X3 is N,
• Z is selected from the group consisting of heteroaryl, and aryl, wherein heteroaryl is selected from the group consisting of thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, isothiazolyl, triazolyl, thiadiazolyl, oxadiazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, tetrazolyl, and triazinyl, and wherein any of such heteroaryl and aryl may be optionally substituted by one or more groups selected from (C1-C3)alkyl, halo, CN, and (RARB)NC(O)—;
• R1 is H;
• R2 is selected from the group consisting of heteroaryl(C1-C4)alkyl-, and (C3-C8)heterocycloalkyl-(C1-C6)alkyl-, wherein any of such alkyl, heteroaryl and heterocycloalkyl may be optionally substituted by one or more groups selected from (C1-C3)alkyl, halo, RAO(C1-C4)alkylene-, (C1-C6) haloalkyl, and RAO—;
• RA and RB are at each occurrence independently H or (C1-C4)alkyl-, or
• RA and RB may form together with the nitrogen atom to which they are attached a 6-membered saturated heterocyclic monocyclic ring system optionally containing a further heteroatom which is nitrogen, which may be optionally substituted by RC(O)C—;
• RC is (C1-C6)alkyl;
• and
• J is H or (RARB)N—.