Ten patients with previously untreated stage III/IV low grade histology non-Hodgkin's lymphoma received a 1-hour intravenous infusion of Didemnin B 2.3 mg/m2 weekly for 4 weeks repeated every 6 weeks. 40% of patients experienced significant hypersensitivity reactions, one of which was life-threatening, despite premedication with diphenhydramine and cimetidine. Other toxicities included nausea, vomiting, fatigue, diarrhea and skin rashes. No objective responses were seen. Given the serious toxicity and lack of activity in a non-pretreated group of patients, the study was closed early. Further investigation of Didemnin B at this dose and schedule is not recommended.