Antitumor effect of CPT-11, a new derivative of camptothecin, against pleiotropic drug-resistant tumors in vitro and in vivo.

CPT-11, a new derivative of camptothecin, was effective against tumor cells, especially vincristine (VCR)-and adriamycin (ADM)-resistant P388 leukemia, compared to either VCR or ADM. The drug showed superior chemotherapeutic effects over VCR and ADM in sensitive P388 leukemia-bearing mice, and was also effective in VCR- and ADM-resistant P388 leukemia-bearing mice. These latter survival advantages with CPT-11 were almost equal to those obtained by CPT-11 against sensitive P388 leukemia. CPT-11 was found to be effective against human tumor cells, especially various pleiotropically drug-resistant human tumor lines, compared to VCR and ADM. CPT-11 should be considered for further development as a new chemotherapeutic agent potentially effective against pleiotropically drug-resistant tumors.