[Early phase II study of MST-16 (sobuzoxane) for breast cancer]

An early phase II study of MST-16 for breast cancer was conducted with the participation of 9 hospitals. MST-16 was administered at three doses; 1) 1,600 mg/body for 5 consecutive days repeating every 4 weeks, 2) 1,200 mg/body for 10-14 consecutive days every 5 weeks, and 3) 1,200 mg/body daily for at least 4 weeks. A total of 28 patients were entered, and 27 cases were eligible. Twenty-five cases were evaluated for efficacy and 27 cases for safety. One patient achieved complete response, 2 patients attained partial response, and the response rate thus obtained was 12.0%. Major side effects observed were myelosuppression represented by leukopenia (69.2%) followed by gastrointestinal disorders. These symptoms, however, were reversible by the cessation of administration.