A compound of formula I: in which: Yi is selected from N, NH and CH; Y 2 is selected from N, NH and CH; Y 3 is selected from N and C; Y 4 is selected from N and CH; R 1 is selected from R 1a and -SR 1a; wherein R 1a is selected from phenyl, pyridinyl, pyrazine, pyridazine, 2,3-dihydrobenzofuran and pyrimidine; wherein said phenyl, pyridinyl, pyrazine, pyridazine or pyrimidine is unsubstituted or substituted with 1 to 3 R 4 groups; wherein each R 4 group is independently selected from halo, amino, -NH(C 1-4 alkyl), -N(C 1-4 alkyl) 2, -NH(C 0-1 alkyl-C 3-5 cycloalkyl), morpholino, pyrrolidinyl, hydroxyl, C 1-3 alkyl, C 1-3 alkoxy and halo-substituted-C 1-3 alkyl; wherein said pyrrolidinyl of R 4 can be unsubstituted or substituted with hydroxy; R 2 is selected from H, CH 3 and halo-substituted-C 1-2 alkyl; R 4a and R 4b are each independently selected from hydrogen, hydroxy and fluoro; with proviso that R 4a and R 4b cannot both be OH; R 5a is selected from amino and amino-methyl; R 5b is selected from C 1-6 alkyl, methoxy-carbonyl, C 3-6 cycloalkyl-C 1-3 alkyl, hydroxy-substituted C 1-3 alkyl, C 1-2 alkoxy-substituted C 1-3 alkyl and a 5 to 6 member heteroaryl ring containing 1 to 4 heteroatoms selected from O, S and N; wherein said C 1-6 alkyl or C 1-2 alkoxy-substituted C 1-3 alkyl of R 5b is unsubstituted or substituted with 1-3 fluorines; or R 5a and R 5b, together with the carbon atom to which R 5a and R 5b are attached, form a group selected from: wherein *C represents the carbon atom to which R 5a and R 5b are attached; R 10 is amino; R 11a is selected from hydrogen, hydroxy, fluoro, C 1-2 alkyl and hydroxy-methyl; R 11b is selected from fluoro, methyl and hydrogen; R 11c is selected from hydrogen, C 1-2 alkyl and hydroxy-methyl; R 12 is selected from hydrogen, halo, hydroxy, C 1-3 alkyl, halo-substituted-C 1-3 alkyl, halo-substituted-C 1-3 alkoxy and C 1-3 alkoxy; and R 13 is selected from hydrogen, halo and C 1-2 alkyl; and R 6a and R 6b are each independently selected from hydrogen, hydroxy and fluoro; with proviso that R 6a and R 6b cannot both be OH; or the pharmaceutically acceptable salts thereof. Yi is selected from N, NH and CH; Y 2 is selected from N, NH and CH; Y 3 is selected from N and C; Y 4 is selected from N and CH; R 1 is selected from R 1a and -SR 1a; wherein R 1a is selected from phenyl, pyridinyl, pyrazine, pyridazine, 2,3-dihydrobenzofuran and pyrimidine; wherein said phenyl, pyridinyl, pyrazine, pyridazine or pyrimidine is unsubstituted or substituted with 1 to 3 R 4 groups; wherein each R 4 group is independently selected from halo, amino, -NH(C 1-4 alkyl), -N(C 1-4 alkyl) 2, -NH(C 0-1 alkyl-C 3-5 cycloalkyl), morpholino, pyrrolidinyl, hydroxyl, C 1-3 alkyl, C 1-3 alkoxy and halo-substituted-C 1-3 alkyl; wherein said pyrrolidinyl of R 4 can be unsubstituted or substituted with hydroxy; R 2 is selected from H, CH 3 and halo-substituted-C 1-2 alkyl; R 4a and R 4b are each independently selected from hydrogen, hydroxy and fluoro; with proviso that R 4a and R 4b cannot both be OH; R 5a is selected from amino and amino-methyl; R 5b is selected from C 1-6 alkyl, methoxy-carbonyl, C 3-6 cycloalkyl-C 1-3 alkyl, hydroxy-substituted C 1-3 alkyl, C 1-2 alkoxy-substituted C 1-3 alkyl and a 5 to 6 member heteroaryl ring containing 1 to 4 heteroatoms selected from O, S and N; wherein said C 1-6 alkyl or C 1-2 alkoxy-substituted C 1-3 alkyl of R 5b is unsubstituted or substituted with 1-3 fluorines; or R 5a and R 5b, together with the carbon atom to which R 5a and R 5b are attached, form a group selected from: wherein *C represents the carbon atom to which R 5a and R 5b are attached; R 10 is amino; R 11a is selected from hydrogen, hydroxy, fluoro, C 1-2 alkyl and hydroxy-methyl; R 11b is selected from fluoro, methyl and hydrogen; R 11c is selected from hydrogen, C 1-2 alkyl and hydroxy-methyl; R 12 is selected from hydrogen, halo, hydroxy, C 1-3 alkyl, halo-substituted-C 1-3 alkyl, halo-substituted-C 1-3 alkoxy and C 1-3 alkoxy; and R 13 is selected from hydrogen, halo and C 1-2 alkyl; and R 6a and R 6b are each independently selected from hydrogen, hydroxy and fluoro; with proviso that R 6a and R 6b cannot both be OH; or the pharmaceutically acceptable salts thereof. wherein *C represents the carbon atom to which R 5a and R 5b are attached; R 10 is amino; R 11a is selected from hydrogen, hydroxy, fluoro, C 1-2 alkyl and hydroxy-methyl; R 11b is selected from fluoro, methyl and hydrogen; R 11c is selected from hydrogen, C 1-2 alkyl and hydroxy-methyl; R 12 is selected from hydrogen, halo, hydroxy, C 1-3 alkyl, halo-substituted-C 1-3 alkyl, halo-substituted-C 1-3 alkoxy and C 1-3 alkoxy; and R 13 is selected from hydrogen, halo and C 1-2 alkyl; and R 6a and R 6b are each independently selected from hydrogen, hydroxy and fluoro; with proviso that R 6a and R 6b cannot both be OH; or the pharmaceutically acceptable salts thereof.