Initial clinical trial of the macrophage activator muramyl tripeptide-phosphatidylethanolamine encapsulated in liposomes in patients with advanced cancer.

A phase I clinical trial of the macrophage activator, muramyl tripeptide-phosphatidylethanolamine has been carried out in 37 patients (47 courses) at doses of 0.01-6.0 mg/m2 intravenously twice weekly for 4 weeks. Activation of peripheral blood monocytes and drug toxicity were used as the parameters to monitor the trial. Toxicity was acute systemic responses of fever, chills, and hypertension without a clear dose response. No major organ-related toxicity was seen. A dose of 4.0 mg/m2 biweekly produced activation of blood monocytes; a dose of 6.0 mg/m2 produced inhibition. There was one complete response of 3 months duration in a patient with renal cell carcinoma with pulmonary metastases. The optimum dose for phase II studies is in the range of 1-4 mg/m2 twice weekly for 4 weeks, a dose that is well tolerated.