A compound of formula, or a pharmaceutically acceptable salt thereof: wherein A represents C-R 1 or N; E represents C-R 2; R 1 represents fluoro; R 2 represents hydrogen; R 3 represents -NR 3a R 3b; or R 3 represents a group of formula (Wa): in which the asterisk (*) represents the point of attachment to the remainder of the molecule; and the group of formula (Wa) represents azetidin-1-yl, pyrrolidin-1-yl or morpholin-4-yl, any of which rings may be optionally substituted by one to six substituents independently selected from halogen; R 3a represents hydrogen or C 1-6 alkyl; R 3b represents C 1-6 alkyl or C 3-7 cycloalkyl(C 1-6)alkyl, either of which groups may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkyl, trifluoromethyl, C 1-6 alkylaminocarbonyl and di(C 1-6)alkylaminocarbonyl; R 4a represents C 1-6 alkyl, which group may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkoxy and C 1-6 alkylsulfonyl; and R 4b represents hydrogen, fluoro or C 1-6 alkyl; or R 4a and R 4b, when taken together with the carbon atom to which they are both attached, represent cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, oxetanyl, pyrrolidinyl, tetrahydropyranyl or piperidinyl, any of which groups may be optionally substituted by one or two substituents independently selected from C 1-6 alkyl, halogen, trifluoroethyl and C 2-6 alkoxycarbonyl; and R 6 represents C 3-9 cycloalkyl, aryl or heteroaryl, any of which groups may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkyl and cyclopropyl. A represents C-R 1 or N; E represents C-R 2; R 1 represents fluoro; R 2 represents hydrogen; R 3 represents -NR 3a R 3b; or R 3 represents a group of formula (Wa): in which the asterisk (*) represents the point of attachment to the remainder of the molecule; and the group of formula (Wa) represents azetidin-1-yl, pyrrolidin-1-yl or morpholin-4-yl, any of which rings may be optionally substituted by one to six substituents independently selected from halogen; R 3a represents hydrogen or C 1-6 alkyl; R 3b represents C 1-6 alkyl or C 3-7 cycloalkyl(C 1-6)alkyl, either of which groups may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkyl, trifluoromethyl, C 1-6 alkylaminocarbonyl and di(C 1-6)alkylaminocarbonyl; R 4a represents C 1-6 alkyl, which group may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkoxy and C 1-6 alkylsulfonyl; and R 4b represents hydrogen, fluoro or C 1-6 alkyl; or R 4a and R 4b, when taken together with the carbon atom to which they are both attached, represent cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, oxetanyl, pyrrolidinyl, tetrahydropyranyl or piperidinyl, any of which groups may be optionally substituted by one or two substituents independently selected from C 1-6 alkyl, halogen, trifluoroethyl and C 2-6 alkoxycarbonyl; and R 6 represents C 3-9 cycloalkyl, aryl or heteroaryl, any of which groups may be optionally substituted by one, two or three substituents independently selected from halogen, C 1-6 alkyl and cyclopropyl.