ACTIVITY OF CPT-11 (IRINOTECAN HYDROCHLORIDE), A TOPOISOMERASE-I INHIBITOR, AGAINST HUMAN TUMOR COLONY-FORMING-UNITS

CPT-11 (irinotecan hydrochloride, 7-ethyl-10-[4-(piperidino)-1-piperid ino] carbonyloxy-camptothecin) is a semisynthetic camptothecin derivat ive developed in Japan. The inhibitory activity of CPT-11 against huma n tumor colony-forming units from freshly explanted human tumors was e xplored using a soft agar cloning system. Final CPT-11 concentrations of 0.3-3.0 mu g/ml were used for a 1 h exposure. At a concentration of 3.0 mu g/ml antitumor activity was seen against colorectal, ovarian, nonsmall-cell lung, breast cancer and mesothelioma colony-forming unit s. CPT-11 should have activity against a broad spectrum of tumors in p atients.