Topoisomerase I inhibitors. An overview of the camptothecin analogs.

The topoisomerase I inhibitors are an exciting new class of antineoplastic agents currently under clinical development. Analogues of camptothecin with improved toxicity profiles and antitumor activity included CPT-11 and topotecan. CPT-11 has demonstrated activity against a variety of tumor types, particularly colon and lung cancer. Early results with topotecan against ovarian and lung cancer are also encouraging. Combination trials with other antineoplastic agents including cisplatin and etoposide, and early clinical trials with new topoisomerase I inhibitors, such as 9-aminocamptothecin, are underway.