Inhibition of DNA topoisomerases II and/or I by pyrazolo[1,5-a]indole derivatives and their growth inhibitory activities.

DNA topoisomerases (topos) I and II are molecular targets of several potent anticancer agents. Thus inhibitors of these enzymes are potential candidates or model compounds for anticancer drugs. We found some of the totally synthetic pyrazolo[1,5-a]indole derivatives, GS-2, -3, and -4, to be strong inhibitors of topo II, and GS-5 was found to be a dual inhibitor of topos I and II (IC(50) values were in the range of 10-30 microM).