Camptothecins selectively target topoisomerase I (Top1) by trapping the catalytic
intermediate of the Top1-DNA reaction, the cleavage complex. Hence, camptothecins
represent a paradigm for targeting macromolecular interactions. Instead of preventing the
binding of the two macromolecules they target (Top1 and DNA), camptothecins slow
down the dissociation of these macromolecules.