Therapeutic agents

A compound of formula (I)

• or a pharmaceutically acceptable salt thereof wherein HET represents a group selected from:
• a) a group of formula A
• b) a group of formula B
• c) a group of formula C
• d) a group of formula D
• e) a group of formula E
• f) a group of formula F
• and
• g) a group of formula G
• wherein
• R1 represents a) a C1-10alkoxy group optionally substituted by one or more fluoro b) a group of formula phenyl(CH2)pO— in which p is 1, 2 or 3 and the phenyl ring is optionally substituted by 1, 2 or 3 groups represented by Z, c) a group R5S(O)2O in which R5 represents a C1-10alkyl group optionally substituted by one or more fluoro or d) halo or e) a C1-4alkyl group;
• m is 0, 1, 2 or 3;
• R2 represents a C1-3alkyl group, a C1-3alkoxy group, hydroxy, nitro, cyano or halo;
• n is 0, 1, 2 or 3;
• R3 represents a) cyclohexyl optionally substituted by one or more of the following:
• hydroxy, fluoro, amino, mono or di C1-3alkylamino b) piperidino optionally substituted by one or more hydroxy c) phenyl optionally substituted by one or more of the following:
• hydroxy, halo or a C1-4alkyl group d) pyridyl optionally substituted by a C1-4alkyl group or e) a C4-9alkyl group;
• and
• R4 represents H, a C1-6alkyl group, a C1-6alkoxy group or a C1-6alkoxyC1-6alkylene group which contains a maximum of 6 carbon atoms, each of which groups is optionally substituted by one or more hydroxy, fluoro, amino, monoC1-4alkylamino, diC1-4alkylamino or cyano.