Benzo[alpha]phenazin-11-carboxamide derivatives and their use as joint inhibitors of topomerase I and II

A compound which is a benzo[a]phenazine-11-carboxamide derivative of formula (I) wherein each of R1 to R4, which are the same or different, is selected from hydrogen, halogen, hydroxyl, C1-C6 alkoxy which is unsubstituted or substituted, heteroaryloxy, C1-C6 alkyl which is unsubstituted or substituted, nitro, cyano, azido, amidoxime, CO2R10, CON(R12)2, OCON(R12), SR10, SOR11, SO2(R11), SO2N(R12)2, N(R12)2, NR10SO2R11, N(SO2R11)2, NR10(CH2)nCN, NR10COR11, OCOR11 or COR10; each of R5 to R7, which are the same or different, is selected from hydrogen, halogen, hydroxy, C1-C6 alkoxy, C1-C6 alkyl, SR10 and N(R12)2; Q is C1-C6 alkylene which is unsubstituted or substituted by (i) C1-C6 alkyl which is unsubstituted or substituted, (ii) hydroxy, provided that the hydroxy group is not a to either of the N atoms adjacent to Q in formula (I), (iii) CO2R10, or (iv) CON(R12); R8 and R9, which are the same or different, are each hydrogen or C1-C6 alkyl, or R8 and R9 together with the nitrogen atom to which they are attached form a saturated 5- or 6-membered N-containing heterocyclic ring which may include one additional heteroatom selected from O, N and S, or one of R8 and R9 is an alkylene chain optionally interrupted by O, N or S, which is attached to a carbon atom on the alkylene chain represented by Q to complete a saturated 5- or 6-membered N-containing heterocyclic ring as defined above; or a pharmaceutically acceptable salt thereof; with the proviso that at least one R1 to R4 is other than hydrogen. These compounds are inhibitors of topoisomerase I and/or topoisomerase II and can be used to treat tumours, including tumours which express MDR.