Homoharringtonine: a phase I evaluation.

Homoharringtonine is one of several Cephalotaxine esters which have shown experimental antineoplastic activity as well as anti-leukemia effects in patients in China. In a Phase I trial of homoharringtonine administered daily X 5 by bolus intravenous injection, the dose limiting toxicity was hypotension and the maximum tolerated dose was 3.5 mg/m2/d X 5. Evidence of drug induced cardiac irritability with resulting ventricular and atrial dysrhythmias was seen. Minimal myelosuppression was seen at this dose. Treatment of patients by 5 day continuous intravenous (rather than bolus) infusion resulted in more pronounced myelosuppression and clinically significant but tolerable hypotension. Significant reduction of white blood cell and platelet counts occurred at a dose of 3.5 mg/m2/day. Further investigations of the hypotensive and cardiac effects of homoharringtonine and Phase II trials using continuous infusion are indicated.