A compound of formula Ia, or Ib wherein Z is O or S; R 1 and R 2 are independently selected from the group consisting of H, halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5-to 7-membered heteroaryl, -OR 6, -CN, -NO 2, -C R 6, -CO 2 R 6, -C NR 6 R 7, -OS R 6, -OS 2 R 6, -SR 6, -S R 6, -S 2 R 6, -S NR 6 R 7, -S 2 NR 6 R 7, -OS NR 6 R 7, -OS 2 NR 6 R 7, and -NR 6 R 7; wherein each hydrogen atom in C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl or C 3 -C 6 cycloalkyl is independently optionally substituted with halogen; R 3 is H, halogen, or C 1 -C 6 alkyl, wherein each hydrogen atom in C 1 -C 6 alkyl, is independently optionally substituted with halogen; R 4 and R 5 are each independently selected from the group consisting of H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl), -C 1 -C 6 alkyl-(C 6 -C 10 aryl), 3- to 7-membered heterocycloalkyl, C 6 -C 10 aryl and 5- to 7-membered heteroaryl, wherein each hydrogen atom in C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl) or -C 1 -C 6 alkyl-(C 6 -C 10 aryl) is independently optionally substituted with halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5- to 7-membered heteroaryl, -OR 8, -CN, - NO 2, -C R 8, -CO 2 R 8, -C NR 8 R 9, -OS R 8, -OS 2 R 8, -SR 8, -S R 8, -S 2 R 8, -S NR 8 R 9, -S 2 NR 8 R 9, -OS NR 8 R 9, -OS 2 NR 8 R 9, and -NR 8 R 9; each of R 6, R 7, R 8, R 9, R 11 and R 12 is independently selected from the group consisting of H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl), -C 1 -C 6 alkyl-(C 6 -C 10 aryl), 3- to 7-membered heterocycloalkyl and C 6 -C 10 aryl R 10 is selected from the group consisting of halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5- to 7-membered heteroaryl, -OR 11, -CN, -NO 2, -C R 11, -CO 2 R 11, -C NR 11 R 12, -OS R 11, -OS 2 R 11, -SR 11, -S R 11, -S 2 R 11, -S NR 11 R 12, -S 2 NR 11 R 12, -OS NR 11 R 12, -OS 2 NR 11 R 12, and -NR 11 R 12; and - - - - - is either a single bond or a pi-bond; or a pharmaceutically acceptable salt thereof for use in a method of treating cancer in a patient, wherein at least one additional cancer therapy is administered. Z is O or S; R 1 and R 2 are independently selected from the group consisting of H, halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5-to 7-membered heteroaryl, -OR 6, -CN, -NO 2, -C R 6, -CO 2 R 6, -C NR 6 R 7, -OS R 6, -OS 2 R 6, -SR 6, -S R 6, -S 2 R 6, -S NR 6 R 7, -S 2 NR 6 R 7, -OS NR 6 R 7, -OS 2 NR 6 R 7, and -NR 6 R 7; wherein each hydrogen atom in C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl or C 3 -C 6 cycloalkyl is independently optionally substituted with halogen; R 3 is H, halogen, or C 1 -C 6 alkyl, wherein each hydrogen atom in C 1 -C 6 alkyl, is independently optionally substituted with halogen; R 4 and R 5 are each independently selected from the group consisting of H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl), -C 1 -C 6 alkyl-(C 6 -C 10 aryl), 3- to 7-membered heterocycloalkyl, C 6 -C 10 aryl and 5- to 7-membered heteroaryl, wherein each hydrogen atom in C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl) or -C 1 -C 6 alkyl-(C 6 -C 10 aryl) is independently optionally substituted with halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5- to 7-membered heteroaryl, -OR 8, -CN, - NO 2, -C R 8, -CO 2 R 8, -C NR 8 R 9, -OS R 8, -OS 2 R 8, -SR 8, -S R 8, -S 2 R 8, -S NR 8 R 9, -S 2 NR 8 R 9, -OS NR 8 R 9, -OS 2 NR 8 R 9, and -NR 8 R 9; each of R 6, R 7, R 8, R 9, R 11 and R 12 is independently selected from the group consisting of H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, -C 1 -C 6 alkyl-(C 3 -C 6 cycloalkyl), -C 1 -C 6 alkyl-(C 6 -C 10 aryl), 3- to 7-membered heterocycloalkyl and C 6 -C 10 aryl R 10 is selected from the group consisting of halogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 3- to 7-membered heterocycloalkyl, 5- to 7-membered heteroaryl, -OR 11, -CN, -NO 2, -C R 11, -CO 2 R 11, -C NR 11 R 12, -OS R 11, -OS 2 R 11, -SR 11, -S R 11, -S 2 R 11, -S NR 11 R 12, -S 2 NR 11 R 12, -OS NR 11 R 12, -OS 2 NR 11 R 12, and -NR 11 R 12; and - - - - - is either a single bond or a pi-bond; or a pharmaceutically acceptable salt thereof for use in a method of treating cancer in a patient, wherein at least one additional cancer therapy is administered.