A compound of formula wherein, R 1 is selected from -H or -C 1-3 alkyl and R 2 is -C 1-3 alkyl; or R 1 is -C 1-3 alkyl and R 2 is selected from -H, -C 1-3 alkyl, -C 1-3 haloalkyl, -NH 2, - NH-C 1-3 alkyl, halogen; R 3 is -C 1-4 alkyl substituted with one or more groups independently selected from halogen, -C 1-2 haloalkyl, -O-C 1-3 alkyl, -O-C 1-3 haloalkyl, 4-7 membered heterocycloalkyl, -C 3-7 cycloalkyl, phenyl and 5-6 membered heteroaryl, wherein the phenyl and the 5-6 membered heteroaryl groups can be optionally substituted with one or more groups independently selected from halogen and -C 1-2 alkyl; X 1 is -CH= or -N= X 2 is --CR 7 = or -N=, wherein X 1 is -CH= and X 2 is -N=, or X 1 is -N= and X 2 is -CH=, or X 1 is - CH= and X 2 is -CR 7 = X 3 is --CR 8 = or -N=; X 4 is -CR 4 = or -N=; X 5 is -CR 5 = or -N=; X 6 is -CH= or -N=; with the proviso that none or only one or two among X 3, X 4, X 5 and X 6 are - N=; R 4 is selected from -H, halogen, -CN, -NH 2, -O-R 6, -N(C 1-3 alkyl) 2, - C N(C 1-3 alkyl) 2 and -C 1-5 alkyl, wherein the -C 1-5 alkyl group can be optionally and independently substituted with one or more groups independently selected from halogen or -CN, or R 4 is selected from 5-6 membered heteroaryl and 4-7 membered heterocycloalkyl, wherein the heteroaryl groups can be optionally and independently substituted with one or more groups independently selected from -C 1-3 alkyl, and the heterocycloalkyl group can be optionally and independently substituted with one or more groups independently selected from -C 1-3 alkyl or =O, or R 4 is a -C 3-6 cycloalkyl wherein the cycloalkyl group can be optionally and independently substituted with one or more groups independently selected from C 1-3 alkyl, -C 1-3 haloalkyl and halogen; R 5 is selected from -H, halogen, -NH 2, -C 1-3 alkyl, -SO 2 N(C 1-3 alkyl) 2 and 5-6 membered heterocycloalkyl, which heterocycloalkyl can be optionally substituted with one or more groups independently selected from =O, - C 1-3 alkyl, and -C 1-5 haloalkyl; R 6 is selected from 4-7 membered heterocycloalkyl, -C 3-7 cycloalkyl and -C 1-5 alkyl, wherein the -C 1-5 alkyl group can be optionally substituted with-C 3-7 cycloalkyl, R 7 is selected from -H, -C 1-5 alkyl and -O-C 1-5 alkyl; R 8 is -H or -C 1-3 alkyl; wherein the compounds of formula may be optionally be present in the form of salts. R 1 is selected from -H or -C 1-3 alkyl and R 2 is -C 1-3 alkyl; or R 1 is -C 1-3 alkyl and R 2 is selected from -H, -C 1-3 alkyl, -C 1-3 haloalkyl, -NH 2, - NH-C 1-3 alkyl, halogen; R 3 is -C 1-4 alkyl substituted with one or more groups independently selected from halogen, -C 1-2 haloalkyl, -O-C 1-3 alkyl, -O-C 1-3 haloalkyl, 4-7 membered heterocycloalkyl, -C 3-7 cycloalkyl, phenyl and 5-6 membered heteroaryl, wherein the phenyl and the 5-6 membered heteroaryl groups can be optionally substituted with one or more groups independently selected from halogen and -C 1-2 alkyl; X 1 is -CH= or -N= X 2 is --CR 7 = or -N=, wherein X 1 is -CH= and X 2 is -N=, or X 1 is -N= and X 2 is -CH=, or X 1 is - CH= and X 2 is -CR 7 = X 3 is --CR 8 = or -N=; X 4 is -CR 4 = or -N=; X 5 is -CR 5 = or -N=; X 6 is -CH= or -N=; with the proviso that none or only one or two among X 3, X 4, X 5 and X 6 are - N=; R 4 is selected from -H, halogen, -CN, -NH 2, -O-R 6, -N(C 1-3 alkyl) 2, - C N(C 1-3 alkyl) 2 and -C 1-5 alkyl, wherein the -C 1-5 alkyl group can be optionally and independently substituted with one or more groups independently selected from halogen or -CN, or R 4 is selected from 5-6 membered heteroaryl and 4-7 membered heterocycloalkyl, wherein the heteroaryl groups can be optionally and independently substituted with one or more groups independently selected from -C 1-3 alkyl, and the heterocycloalkyl group can be optionally and independently substituted with one or more groups independently selected from -C 1-3 alkyl or =O, or R 4 is a -C 3-6 cycloalkyl wherein the cycloalkyl group can be optionally and independently substituted with one or more groups independently selected from C 1-3 alkyl, -C 1-3 haloalkyl and halogen; R 5 is selected from -H, halogen, -NH 2, -C 1-3 alkyl, -SO 2 N(C 1-3 alkyl) 2 and 5-6 membered heterocycloalkyl, which heterocycloalkyl can be optionally substituted with one or more groups independently selected from =O, - C 1-3 alkyl, and -C 1-5 haloalkyl; R 6 is selected from 4-7 membered heterocycloalkyl, -C 3-7 cycloalkyl and -C 1-5 alkyl, wherein the -C 1-5 alkyl group can be optionally substituted with-C 3-7 cycloalkyl, R 7 is selected from -H, -C 1-5 alkyl and -O-C 1-5 alkyl; R 8 is -H or -C 1-3 alkyl;