NEW PERSPECTIVES IN COLON-CANCER CHEMOTHERAPY

Camptothecin and some of its derivatives, all inhibitors of topoisomer ase I, have been found to inhibit growth and induce regression of huma n colon carcinoma xenografts in nude mice. Some clinical trials of the se compounds have been already completed, many more are being held. Th e mother compound, camptothecin, which is water insoluble, has been ad ministered orally in a Phase I clinical trial. Main toxicity encounter ed has been diarrhea with minimal leukocytopenia. Camptothecin is now in Phase 2 clinical trials. 9-Aminocamptothecin, a water-insoluble der ivative, is now in Phase I trials. Topotecan and iridotecan, two water -soluble derivatives, have undergone Phase I trials, showing mostly in testinal toxicity, followed by bone marrow depression.