Intravenous infusion of high doses of liposomes containing NSC 251635, a water-insoluble cytostatic agent. A pilot study with pharmacokinetic data.

In patients with resistant malignant tumors, we performed a pilot trial of intravenous infusion of a water-insoluble cytostatic agent, NSC 251635, entrapped in large volumes of liposomes made of egg yolk lecithin, cholesterol, and stearylamine (4:3:1). Forty liposome infusions were given to 14 patients in 38 courses. The volume of liposomes (20 mg of lipids/mL) varied from 205 to 1,000 mL or 124 to 617 mL/m2 of body surface, and amounts of NSC 251635 varied from 82 to 456 mg/m2. Three patients received repeated single courses. Liposomal therapy was very well tolerated. Side effects observed during some infusions were mild sedation, fever, chills, lumbar pain, urticarial rash, and bronchospasm. In all patients investigated, an important activation of the complement system was observed. No objective regression of the tumors was observed. The limiting factor in the phase I study was not toxicity but the volume of liposomes that could be prepared at once because of the long time required for its preparation. Pharmacokinetic data showed that maximal serum phospholipid and NSC 251635 concentrations were obtained at the end of the liposome infusion. The drug's peak was followed by a decreasing phase leading to a kind of plateau and a prolonged presence of the drug in the blood until 120 hours after its administration. Comparison of the pharmacokinetics of phospholipids and NSC 251635 suggests a rather rapid dissociation of the drug from the liposome.