Treatment of adult T-cell leukemia/lymphoma with MST-16, a new oral antitumor drug and a derivative of bis(2,6-dioxopiperazine). The MST-16 Study Group

MST-16, a new orally administered bis(2,6-dioxopiperazine) analogue and an inhibitor of topoisomerase II, was given to 24 patients with adult T-cell leukemia-lymphoma (ATLL) in a Phase I-II multi-institutional cooperative study. MST-16 was administered orally daily for 7 days, with courses repeated at intervals of 2-3 weeks in 24 patients. Two complete remissions (CR) and eight partial remissions (PR) were obtained in 23 evaluable patients who received 1200-2800 mg/day of MST-16. Among 13 acute-type ATLL, one CR and five PR were obtained. Among eight lymphoma-type ATLL, two PR were detected. Among two chronic-type ATLL, one CR and one PR occurred. Remissions were obtained at 7-232 days (median, 23 days) and lasted 43-374 days (median, 68 days). The major toxic effects were leukopenia (68%), anemia (52%), thrombocytopenia (35%), and gastrointestinal disorders (22%). MST-16 was shown to be effective in ATLL, which has no standard therapy. This drug deserves further clinical trials because it shows little cross resistance to currently available antitumor drugs.