There is a critical need to find new chemotherapeutic agents that are active in platinum-refractory ovarian cancer. A phase II trial of zeniplatin (CL 286,558), a third-generation platinum compound, was conducted in 31 patients with advanced ovarian cancer to examine the safety and activity of the agent when used as a salvage treatment in individuals previously exposed to organoplatinum-based therapy. In general the drug was well tolerated, with moderate emesis and bone marrow suppression being observed in most patients. An unexpected side-effect was significant fever, of unknown etiology, which was noted in 16% of patients. Out of 20 patients, 2 (10%; 95% confidence intervals: 1%-32%) with clinically defined platinum-refractory disease achieved a partial response. Unfortunately, although we have defined definite but modest activity for zeniplatin in platinum-refractory ovarian cancer, further development of this drug has been discontinued because of the severe renal toxicity observed in other clinical trials of this cytotoxic agent.