A compound of formula (I): ** Formula ** or a pharmaceutically acceptable salt, solvate or polymorph thereof, including all tautomers and stereoisomers thereof, wherein: R 1 represents -C 1-6 alkyl, -aryl, - C 1-6 alkyl-aryl, -cycloalkyl, -C 1-6 alkyl-cycloalkyl, -heteroaryl, -C 1-6 alkyl-heteroaryl, -heterocyclyl, -C 1-6 alkyl-heterocyclyl, -cycloalkyl substituted with phenyl, -cycloalkyl substituted with phenoxy, -phenyl substituted with cycloalkyl, -phenyl substituted with phenyl, -phenyl substituted with phenyl, heterocyclyl substituted with phenyl, heteroaryl substituted with phenyl, phenyl substituted with heterocyclyl, phenyl substituted with heteroaryl, phenyl substituted with -O-cycloalkyl or substituted phenyl with -cycloalkyl-heterocyclyl； and wherein any of the aforementioned aryl, cycloalkyl, heterocyclyl, heteroaryl, phenyl or phenoxy groups may be optionally substituted with one or more groups selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl, -C1-6thioalkyl, -SO-C1-4alkyl, -SO2-C1-4alkyl, C1-6alkoxy-, -C3-8cycloalkyl, C3-8cycloalkyl, -SO2-C3-8cycloalkyl, -SO- C3-6 cycloalkyl, C3-6 alkenyloxy, C3-6- alkynyloxy, -C (O) -C1-6 alkyl, -C (O) O-C1-6 alkyl, C1-6 alkoxy-C1-6 alkyl- , nitro, halogen, cyano, hydroxyl, -C (O) OH, - NH2, -NH-C1-4 alkyl, -N (C1-4 alkyl) (C1-4 alkyl), -C (O) N (alkyl C1-4) (C1-4 alkyl), -C (O) NH2, -C (O) NH (C1-4 alkyl) and -C (O) NH (C3-10 cycloalkyl)； R 2 represents -C 1-6 alkyl, C 1-6 haloalkyl, -aryl, -C 1-6 alkyl-aryl, -cycloalkyl, -C 1-6 alkyl-cycloalkyl, -heteroaryl, -C 1-6 alkyl-heteroaryl, -heterocyclyl or - C1-6 alkyl heterocyclyl； and wherein any of the aforementioned aryl, heteroaryl or heterocyclyl groups may be optionally substituted with one or more groups selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl, C1-6 thioalkyl, -SO-C1-4 alkyl, -SO2-C1-4 alkyl, C1-6 alkoxy, -O-C3-8 cycloalkyl, C3-8 cycloalkyl, -SO2-C3-8 cycloalkyl, -SO-C3-6 cycloalkyl , C3-6- alkenyloxy, C3-6- alkynyl
