A compound of formula (I) ** Formula ** in which: R1 is alkyl of 1-6 carbon atoms, cycloalkyl of 3-6 carbon atoms, or heterocyclyl, all of which are optionally substituted with 1, 2, 3 or 4 substituents selected from halo, oxo, alkyl of 1-6 carbon atoms, cycloalkyl of 3-8 carbon atoms, heterocyclyl, phenyl, phenoxy, -CN, -O-R6, -C (O) -R6, - OC (O) -R6, -C (O) -O-R6, - N (R6) -C (O) -O-R7, -N (R6) -C (O) -R7, -N (R6 ) -C (O) -N (R6) (R7) and - C (O) -N (R6) (R7), wherein alkyl, cycloalkyl, heterocyclyl, phenyl and phenoxy are optionally substituted with 1, 2 or 3 substituents selected from alkyl of 1-6 carbon atoms, cycloalkyl of 3-8 carbon atoms, alkoxy of 1-6 carbon atoms, hydroxyl, and halo； wherein R6 and R7 are independently selected from the group consisting of hydrogen, alkyl of 1-6 carbon atoms and cycloalkyl of 3-8 carbon atoms； or R6 and R7 when taken together with the nitrogen to which they are attached form a heterocycle； R2 is aryl, heteroaryl or heterocyclyl, all of which are optionally substituted with 1, 2 or 3 substituents selected from alkyl of 1-6 carbon atoms, alkoxy of 1-6 carbon atoms, cycloalkyl of 3-8 carbon atoms, cycloalkylalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, heterocyclyl, heterocyclylalkyl, halo, haloalkoxy, oxo, -CN, -O-R6, -OC (O) -R6, -OC (O) -N (R6) (R7), -S-R6, -N (R6) (R7), - S (>； = O) - R6, -S (>； = O) 2R6, -S (>； = O) 2-N (R6) (R7), -S (>； = O) 2-O-R6, -N (R6) -C (O) -R7, -N (R6) -C (O) -O-R7, -N (R6) -C (O ) -N (R6) (R7), - C (O) -R6, -C (O) -O-R6, -C (O) -N (R6) (R7) and -N (R6) -S ( >； = O) 2-R7, wherein the alkyl, alkoxy, cycloalkyl, aryl, heteroaryl or heterocyclyl are also optionally substituted with one or more substituents selected from halo, hydroxyl, oxo, -CN and -O-R6； with the proviso that the heteroaryl or heterocyclyl moiety includes at least one atom of nitrogen in the ring； R4 and R5 are independently hydrogen, halo, cyano, alkyl of 1-6 carbon atoms, alkoxy of 1-6 carbon atoms or cycloalky
