Population pharmacokinetics of PM00104 (Zalypsis^®) in cancer patients

The aim of this study was to characterize the population pharmacokinetics of PM00104 (Zalypsis^®) in cancer patients.

A total of 135 patients included in four phase I clinical trials who receive intravenous PM00104 at doses ranging from 53 to 5,000 μg/m² and administered as 1-, 3-, or 24-h infusion every 3 weeks or as 1-h infusion on days 1, 8, and 15 of a 28-day cycle, or 1-h infusion daily during 5 consecutive days every 3 weeks were included in the analysis. Pharmacokinetic data were analyzed with non-linear mixed effect model using NONMEM VI software. The effect of selected patient covariates on PM00104 pharmacokinetics was investigated. Model evaluation was performed using predictive checks and non-parametric bootstrap.

An open four-compartment catenary linear model with first-order elimination was developed to best describe the data. Plasma clearance and its between-subject variability was 43.7 L/h (34%). Volume of distribution at steady state was 822 L (117%). Within the range of covariates studied, age, sex, body size variables, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin, lactate dehydrogenase, creatinine clearance, albumin, total protein, hemoglobin, performance status, liver metastases, dose-limiting toxicity, and stable disease for 3 months were not statistically related to PM00104 pharmacokinetic parameters. Bootstrap and posterior predictive check evidenced the model was deemed appropriate to describe the time course of PM00104 plasma concentrations in cancer patients.

The integration of phase I pharmacokinetic data demonstrated PM00104 linear elimination from plasma, dose proportionality up to 5,000 μg/m², and time-independent pharmacokinetics. No clinically relevant covariates were identified as predictors of PM00104 pharmacokinetics.