Phase II evaluation of didemnin B in hormonally refractory metastatic prostate cancer. A Southwest Oncology Group study.

Didemnin B, a dipsipeptide isolated from the Caribbean tunicate Trididemnum with antitumor and antiviral activity was evaluated in a phase II trial in the treatment of metastatic, hormonally refractory adenocarcinoma of the prostate. Thirteen patients were treated with didemnin B at 3.5 mg/m2 and 20 patients were treated at 6.3 mg/m2 intravenously every 28 days. Response was assessed every 8 weeks. Of 32 evaluable patients there was one partial response for an overall response rate of 3% (95% confidence interval of 0.1-16%). The most common toxicities were nausea, vomiting, and diarrhea. Serious cardiac and pulmonary toxicities were also noted. This drug does not appear to warrant further evaluation in this disease as a single agent.