SN-398 is a derivative of Camptothecin , which is an antitumor drug. Acting by inhibiting mammalian DNA topoisomerase I ( Topo I ), stabilizing the Topo I-DNA complex prevents DNA rewiring to induce Topo I mediated DNA breaks. In Hela cell tests, SN-398 shows stronger antitumor activity than SN-38 ( IC 50 =1.562 μM). SN-398 can be used to study the anti-proliferation and growth inhibition of Topo I in cancer cells.