Background Polymeric micellar paclitaxel (PM-paclitaxel) is a novel Cremophor EL-free, nanoparticle-encapsulated paclitaxel formulation administered through intravenous injection. The primary objective of this phase I trial was to determine the first cycle dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of PM-paclitaxel. Secondary objectives included the evaluation of the safety, antitumor activity, and pharmacokinetic (PK) profile of PM-paclitaxel in patients with advanced malignancies. Methods The PM-paclitaxel dose was escalated from 175 mg/m2 (level 1) to 435 mg/m2 (level 5). PM-paclitaxel was intravenously administered to patients for 3 h without premedication on day 1 of a 21-day cycle. Results Eighteen patients with confirmed advanced malignancies received PM-paclitaxel. DLT included grade 4 neutropenia (four patients) and grade 3 numbness (one patient), which occurred in one of the six patients who received 300 mg/m2 (level 3) PM-paclitaxel and all three patients who were treated with 435 mg/m2 PM-paclitaxel. Thus, the MTD of PM-paclitaxel was determined as 390 mg/m2 (level 4). Acute hypersensitive reactions were not observed. Partial response was observed in six of 18 patients (33.3%), three of whom had prior exposure to paclitaxel chemotherapy. The peak concentration and area under the curve values of paclitaxel increased with increasing dosage, indicating that PM-paclitaxel exhibits linear PKs. Conclusions PM-paclitaxel showed high MTD without additional toxicity, and exhibited desirable antitumor activity. The recommended dose of PM paclitaxel for phase II study is 300 mg/m2.
Keywords: Nanoparticle; Paclitaxel; Phase I; Polymeric micelle; Solid malignancies.