Population Pharmacokinetics of Apalutamide and its Active Metabolite N-Desmethyl-Apalutamide in Healthy and Castration-Resistant Prostate Cancer Subjects

• Published in: Clinical pharmacokinetics Vol. 59; no. 2; pp. 229 - 244
• Main Authors: Pérez-Ruixo, Carlos, Pérez-Blanco, Jonás Samuel, Chien, Caly, Yu, Margaret, Ouellet, Daniele, Pérez-Ruixo, Juan-José, Ackaert, Oliver
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.02.2020; Springer Nature B.V
• Subjects: Androgens; Cancer therapies; FDA approval; Health sciences; Internal Medicine; Laboratories; Medicine; Medicine & Public Health; Metastasis; Original Research Article; Pharmacokinetics; Pharmacology/Toxicology; Pharmacotherapy; Population; Prostate cancer; Studies; United States > US
• ISSN: 0312-5963; 1179-1926; 1179-1926
• DOI: 10.1007/s40262-019-00808-7

Background Apalutamide is a next-generation androgen receptor inhibitor approved for treatment of subjects with high-risk, non-metastatic, castration-resistant prostate cancer (NM-CRPC). Objective The objective of this study was to characterize the population pharmacokinetics of apalutamide and its metabolite N -desmethyl-apalutamide in healthy male and castration-resistant prostate cancer subjects. Methods Plasma concentration data for apalutamide and N-desmethyl-apalutamide from 1092 subjects (seven clinical studies) receiving oral apalutamide (30–480 mg) once daily were pooled for a population pharmacokinetic analysis using a non-linear mixed-effect modelling approach. The impact of clinically relevant covariates was also assessed. Results Apalutamide absorption was rapid, and the apparent steady-state volume of distribution was large (276 L), reflecting a wide body distribution. Apalutamide was eliminated slowly, with its apparent clearance increasing from 1.31 L/h after the first dose to 2.04 L/h at steady state. No evidence of time-dependent disposition was observed for N -desmethyl-apalutamide, which was also widely distributed and slowly cleared (1.5 L/h). After 4 weeks of treatment, more than 95% of steady-state exposure of apalutamide and N-desmethyl-apalutamide was reached. At a dose of apalutamide 240 mg/day, apalutamide and N -desmethyl-apalutamide exposure exhibited 5.3- and 85.2-fold accumulation in plasma, respectively. Inter-individual variability in apalutamide apparent clearance is low (< 20%). Among the covariates evaluated, apalutamide and N -desmethyl-apalutamide exposure were statistically associated only with health status, body weight, and albumin concentration, and the effect was low (< 25%). Conclusions A population pharmacokinetic modelling approach was successfully applied to describe the pharmacokinetics of apalutamide and N -desmethyl-apalutamide. No clinically relevant covariates were identified as predictors of apalutamide and N -desmethyl-apalutamide pharmacokinetics.