A compound of formula: wherein: R 1a is H or methyl; R 1b is H or fluoro; A is group (Ab), (Ac) or (Ad): wherein group (Ab) is: wherein: R 4 is H, C 1-4 alkyl or C 1-4 alkylene(aryl); wherein said aryl is optionally substituted by 1, 2 or 3 substituents each independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 4a R 4b, SO 2 R 4c and NHSO 2 R 4c; R 4a is selected from H and C 1-4 alkyl; R 4b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 4c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 5 is H or C 1-4 alkyl; each R 6 is independently C 1-4 alkyl or halo; n is 0, 1, 2 or 3; wherein group (Ac) is: wherein: R 7 is C 1-4 alkyl, C 1-4 alkylene or C 1-4 alkyleneOC 1-4 alkyl; o is 1 or 2; wherein group (Ad) is: wherein: X is a bond, O or CH 2; each R 8 is independently halo, C 1-4 alkyl, C 1-4 alkoxy OC 1-4 haloalkyl, OC 1-4 alkylene(C 3-6 cycloalkyl), OC 1-4 alkylene(4-7 membered heterocycloalkyl) or OH; wherein said heterocycloalkyl and cycloalkyl are optionally substituted by 1, 2 or 3 substituents independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 8a R 8b, SO 2 R 8c and NHSO 2 R 8c; R 8a is selected from H and C 1-4 alkyl; R 8b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 8c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; each R 9 is independently halo or C 1-4 alkyl; p is 0, 1 or 2; q is 0, 1, 2, 3 or 4; wherein B is: wherein: R 10 is H, halo or C 1-4 alkyl; D, E and F are each independently C(R 10); or one of D, E and F is N and the two remaining D, E and F groups are independently C(R 10); or a pharmaceutically acceptable salt and/or solvate thereof. R 1a is H or methyl; R 1b is H or fluoro; A is group (Ab), (Ac) or (Ad): wherein group (Ab) is: wherein: R 4 is H, C 1-4 alkyl or C 1-4 alkylene(aryl); wherein said aryl is optionally substituted by 1, 2 or 3 substituents each independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 4a R 4b, SO 2 R 4c and NHSO 2 R 4c; R 4a is selected from H and C 1-4 alkyl; R 4b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 4c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 5 is H or C 1-4 alkyl; each R 6 is independently C 1-4 alkyl or halo; n is 0, 1, 2 or 3; R 4 is H, C 1-4 alkyl or C 1-4 alkylene(aryl); wherein said aryl is optionally substituted by 1, 2 or 3 substituents each independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 4a R 4b, SO 2 R 4c and NHSO 2 R 4c; R 4a is selected from H and C 1-4 alkyl; R 4b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 4c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 5 is H or C 1-4 alkyl; each R 6 is independently C 1-4 alkyl or halo; n is 0, 1, 2 or 3; wherein group (Ac) is: wherein: R 7 is C 1-4 alkyl, C 1-4 alkylene or C 1-4 alkyleneOC 1-4 alkyl; o is 1 or 2; R 7 is C 1-4 alkyl, C 1-4 alkylene or C 1-4 alkyleneOC 1-4 alkyl; o is 1 or 2; wherein group (Ad) is: wherein: X is a bond, O or CH 2; each R 8 is independently halo, C 1-4 alkyl, C 1-4 alkoxy OC 1-4 haloalkyl, OC 1-4 alkylene(C 3-6 cycloalkyl), OC 1-4 alkylene(4-7 membered heterocycloalkyl) or OH; wherein said heterocycloalkyl and cycloalkyl are optionally substituted by 1, 2 or 3 substituents independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 8a R 8b, SO 2 R 8c and NHSO 2 R 8c; R 8a is selected from H and C 1-4 alkyl; R 8b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 8c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; each R 9 is independently halo or C 1-4 alkyl; p is 0, 1 or 2; q is 0, 1, 2, 3 or 4; X is a bond, O or CH 2; each R 8 is independently halo, C 1-4 alkyl, C 1-4 alkoxy OC 1-4 haloalkyl, OC 1-4 alkylene(C 3-6 cycloalkyl), OC 1-4 alkylene(4-7 membered heterocycloalkyl) or OH; wherein said heterocycloalkyl and cycloalkyl are optionally substituted by 1, 2 or 3 substituents independently selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, halo, CN, OH, NR 8a R 8b, SO 2 R 8c and NHSO 2 R 8c; R 8a is selected from H and C 1-4 alkyl; R 8b is selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; R 8c is selected from C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 alkoxy, C 1-4 haloalkyl, aryl and 4-7 membered heterocycloalkyl; each R 9 is independently halo or C 1-4 alkyl; p is 0, 1 or 2; q is 0, 1, 2, 3 or 4; wherein B is: wherein: R 10 is H, halo or C 1-4 alkyl; D, E and F are each independently C(R 10); or one of D, E and F is N and the two remaining D, E and F groups are independently C(R 10); R 10 is H, halo or C 1-4 alkyl; D, E and F are each independently C(R 10); or one of D, E and F is N and the two remaining D, E and F groups are independently C(R 10); or a pharmaceutically acceptable salt and/or solvate thereof.