PHASE-I/II CLINICAL-TRIAL OF DIDEMNIN-B IN NON-SMALL-CELL LUNG-CANCER - NEUROMUSCULAR TOXICITY IS DOSE-LIMITING

Didemnin B (NSC 325 319), a cyclic depsipeptide isolated from a Caribbean tunicate, exhibits potent preclinical antitumor activity. In previous phase I studies, 3.47 mg/m2 was the maximally tolerated dose, with nausea and vomiting being the dose-limiting toxicity. The drug was given in a single bolus infusion over 30 min every 28 days. In the current study, 30 patients presenting with previously treated non-small-cell lung cancer (NSCLC) received 46 courses of the drug at doses ranging from 3.47 to 9.1 mg/m2. Neuromuscular toxicity was dose-limiting. Nausea and vomiting appeared to be correlated with dose levels and were ameliorated by a combination of antiemetics including dexamethasone. Other side effects included a mild rise in hepatic enzymes and an allergic reaction that was preventable by the addition of corticosteroids to the premedication regimen. In all, 2 minor responses were seen among 24 evaluable patients. Because neuromuscular toxicity is dose-limiting, we recommend that routine measurements of creatine kinase and aldolase, a careful neurologic evaluation, and electromyography and muscle biopsy (if indicated) be incorporated into phase II trials. The recommended dose for phase II studies using a single bolus schedule is 6.3 mg/m2, following the premedication of patients with antiemetics.