A compound of formula: or a pharmaceutically acceptable salt, solvate or polymorph thereof, including all tautomers and stereoisomers thereof wherein: R 1 represents hydrogen, halogen, -C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, -aryl, -C 1-6 alkylaryl, - cycloalkyl, -C 1-6 alkylcycloalkyl, -heteroaryl, -C 1-6 alkylheteroaryl, -heterocyclyl, -C 1-6 alkylheterocyclyl, -cycloalkyl substituted by phenyl, -cycloalkyl substituted by phenoxy, - phenyl substituted by cycloalkyl, -phenyl substituted by phenoxy, -phenyl substituted by phenyl, heterocyclyl substituted by phenyl, heteroaryl substituted by phenyl, phenyl substituted by heterocyclyl, phenyl substituted by heteroaryl, phenyl substituted by -O-cycloalkyl, phenyl substituted by -heterocyclyl-phenyl or phenyl substituted by -cycloalkyl-heterocyclyl; and in which any of aforesaid aryl, cycloalkyl, heterocyclyl, heteroaryl, phenyl or phenoxy groups may optionally be substituted by one or more R b groups selected from C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl, -SO 2 C 1-4 alkyl, C 1-6 alkoxy-, C 1-6 haloalkoxy, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, =O, -C OH, -NH 2, -NHC 1-4 alkyl,-N(C 1-4 alkyl)(C 1-4 alkyl), -C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and-C NH(C 3-10 cycloalkyl); R 2 represents -O-C 1-6 alkyl, -NR 3 R 4 or -O-C 1-6 haloalkyl; R 3 and R 4 independently represent hydrogen, C 1-6 alkyl or C 3-8 cycloalkyl; or R 3 and R 4 together with the nitrogen atom to which they are attached may form a heterocyclyl group optionally substituted by one or more R b groups; n represents an integer selected from 0 to 3; and R a represents C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl,-SO 2 C 1-4 alkyl, C 1-6 alkoxy-, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, -C OH, -NH 2, -NHC 1-4 alkyl, -N(C 1-4 alkyl)(C 1-4 alkyl),-C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and -C NH(C 3-10 cycloalkyl). R 1 represents hydrogen, halogen, -C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, -aryl, -C 1-6 alkylaryl, - cycloalkyl, -C 1-6 alkylcycloalkyl, -heteroaryl, -C 1-6 alkylheteroaryl, -heterocyclyl, -C 1-6 alkylheterocyclyl, -cycloalkyl substituted by phenyl, -cycloalkyl substituted by phenoxy, - phenyl substituted by cycloalkyl, -phenyl substituted by phenoxy, -phenyl substituted by phenyl, heterocyclyl substituted by phenyl, heteroaryl substituted by phenyl, phenyl substituted by heterocyclyl, phenyl substituted by heteroaryl, phenyl substituted by -O-cycloalkyl, phenyl substituted by -heterocyclyl-phenyl or phenyl substituted by -cycloalkyl-heterocyclyl; and in which any of aforesaid aryl, cycloalkyl, heterocyclyl, heteroaryl, phenyl or phenoxy groups may optionally be substituted by one or more R b groups selected from C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl, -SO 2 C 1-4 alkyl, C 1-6 alkoxy-, C 1-6 haloalkoxy, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, =O, -C OH, -NH 2, -NHC 1-4 alkyl,-N(C 1-4 alkyl)(C 1-4 alkyl), -C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and-C NH(C 3-10 cycloalkyl); R 2 represents -O-C 1-6 alkyl, -NR 3 R 4 or -O-C 1-6 haloalkyl; R 3 and R 4 independently represent hydrogen, C 1-6 alkyl or C 3-8 cycloalkyl; or R 3 and R 4 together with the nitrogen atom to which they are attached may form a heterocyclyl group optionally substituted by one or more R b groups; n represents an integer selected from 0 to 3; and R a represents C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl,-SO 2 C 1-4 alkyl, C 1-6 alkoxy-, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, -C OH, -NH 2, -NHC 1-4 alkyl, -N(C 1-4 alkyl)(C 1-4 alkyl),-C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and -C NH(C 3-10 cycloalkyl).