[A novel antitumor agent, sobuzoxane (MST-16)]

Sobuzoxane (MST-16) is an analogue of ICRF-159 which was once evaluated on the clinical efficacies in England. Zenyaku Pharm. Ind. in Japan synthesized many derivatives of bis (2,6-dioxopiperazine) and sobuzoxane was selected from the antitumor efficacies, the results of the toxicity tests and pharmacological profiles from these derivative. The compound was a new type topoisomerase II inhibitor, and G2M phase of the cell cycle was most sensitive. The clinical phase studies proved that sobuzoxane was quite effective for the treatment of malignant lymphoma (overall response rate in phase II study 29.7%) and adult T cell leukemia (response rate for acute type: 46.2%). The dose-limiting factor was leukopenia.