A compound of formula, or a pharmaceutically acceptable salt thereof: wherein R 1 represents phenyl, (C 4 -C 7)cycloalkenyl or Het 1, which R 1 group may be unsubstituted or substituted on one or two carbon atoms by substituents R a, and may further be substituted on a nitrogen atom with a substituent R a1; each R a independently represents (C 1 -C 4)alkyl, halo, halo(C 1 -C 4)alkyl, cyano, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy, halo(C 1 -C 4)alkoxy, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, R 6 OC -, or R 6 OC (C 1 -C 4)alkyl-; R a1 represents (C 1 -C 4)alkyl, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, aryl(C 1 -C 4)alkyl- or R 6 OC (C 1 -C 4)alkyl-; R 2 represents (C 1 -C 6)alkyl, (C 3 -C 7)cycloalkyl, (C 4 -C 7)cycloalkenyl, phenyl, furanyl, thiazolyl, thienyl or pyrazolyl, which R 2 may be unsubstituted or substituted on from one to three carbon atoms with substituents R b, and may further be substituted on a nitrogen atom with (C 1 -C 4)aikyl; each R b independently represents (C 1 -C 4)alkyl, halo, halo(C 1 -C 4)alkyl, cyano, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, (R 6) 2 NC (C 1 -C 4)alkyl- or R 6 OC (C 1 -C 4)alkyl-; X represents O, NH or NMe; or X represents -CH 2 -O-, wherein the O atom is attached to the -C(R 4)(R 4') atom of the ring; each R 3 independently represents methyl or ethyl; R 4 represents hydrogen, (C 1 -C 4)alkyl, halo(C 1 -C 4)alkyl, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, amino(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, phenyl, Het 1 (C 1 -C 4)alkyl-, Het 2 (C 1 C 4)alkyl-, (C 1 -C 4)alkylS 2 NH(C 1 -C 4)alkyl-, or R 7 C NH(C 1 -C 4)alkyl-; R 4' represents H or methyl; R 4a represents hydrogen, (C 1 -C 4)alkyl, halo(C 1 -C 4)alkyl, amino(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, Het 1 (C 1 -C 4)alkyl-, Het 2 (C 1 -C 4)alkyl-, or R 6 OC -; R 6 represents hydrogen, (C 1 -C 4)alkyl; R 7 represents (C 1 -C 2)alkyl, (C 1 -C 2)alkoxy, (C 1 -C 2)alkoxy(C 1 -C 2)alkyl or phenyl; Het 1 represents a 5- or 6-membered heteroaryl ring comprising a) one oxygen or sulphur atom and optionally one or two nitrogen atoms; or b) from one to four nitrogen atoms; and Het 2 represents a 4- to 7-membered heterocyclic ring comprising a) 1 or 2 heteroatoms selected from N, O and S; or b) -C - and 1 or 2 heteroatoms selected from N and O. wherein R 1 represents phenyl, (C 4 -C 7)cycloalkenyl or Het 1, which R 1 group may be unsubstituted or substituted on one or two carbon atoms by substituents R a, and may further be substituted on a nitrogen atom with a substituent R a1; each R a independently represents (C 1 -C 4)alkyl, halo, halo(C 1 -C 4)alkyl, cyano, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy, halo(C 1 -C 4)alkoxy, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, R 6 OC -, or R 6 OC (C 1 -C 4)alkyl-; R a1 represents (C 1 -C 4)alkyl, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, aryl(C 1 -C 4)alkyl- or R 6 OC (C 1 -C 4)alkyl-; R 2 represents (C 1 -C 6)alkyl, (C 3 -C 7)cycloalkyl, (C 4 -C 7)cycloalkenyl, phenyl, furanyl, thiazolyl, thienyl or pyrazolyl, which R 2 may be unsubstituted or substituted on from one to three carbon atoms with substituents R b, and may further be substituted on a nitrogen atom with (C 1 -C 4)aikyl; each R b independently represents (C 1 -C 4)alkyl, halo, halo(C 1 -C 4)alkyl, cyano, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, (R 6) 2 NC (C 1 -C 4)alkyl- or R 6 OC (C 1 -C 4)alkyl-; X represents O, NH or NMe; or X represents -CH 2 -O-, wherein the O atom is attached to the -C(R 4)(R 4') atom of the ring; each R 3 independently represents methyl or ethyl; R 4 represents hydrogen, (C 1 -C 4)alkyl, halo(C 1 -C 4)alkyl, hydroxy(C 1 -C 4)alkyl, (C 1 -C 4)alkoxy(C 1 -C 4)alkyl-, amino(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, phenyl, Het 1 (C 1 -C 4)alkyl-, Het 2 (C 1 C 4)alkyl-, (C 1 -C 4)alkylS 2 NH(C 1 -C 4)alkyl-, or R 7 C NH(C 1 -C 4)alkyl-; R 4' represents H or methyl; R 4a represents hydrogen, (C 1 -C 4)alkyl, halo(C 1 -C 4)alkyl, amino(C 1 -C 4)alkyl-, (C 1 -C 4)alkylamino(C 1 -C 4)alkyl-, di[(C 1 -C 4)alkyl]amino(C 1 -C 4)alkyl-, Het 1 (C 1 -C 4)alkyl-, Het 2 (C 1 -C 4)alkyl-, or R 6 OC -; R 6 represents hydrogen, (C 1 -C 4)alkyl; R 7 represents (C 1 -C 2)alkyl, (C 1 -C 2)alkoxy, (C 1 -C 2)alkoxy(C 1 -C 2)alkyl or phenyl; Het 1 represents a 5- or 6-membered heteroaryl ring comprising a) one oxygen or sulphur atom and optionally one or two nitrogen atoms; or b) from one to four nitrogen atoms; and Het 2 represents a 4- to 7-membered heterocyclic ring comprising a) 1 or 2 heteroatoms selected from N, O and S; or b) -C - and 1 or 2 heteroatoms selected from N and O.