Pharmacokinetics and Safety of Enzalutamide in Healthy Chinese Male Volunteers.

PURPOSE: This open-label, single-dose study evaluated the pharmacokinetic profiles of enzalutamide and its major metabolites and the safety of enzalutamide in healthy, Chinese male volunteers.

METHODS: Fourteen volunteers (median age, 28.5 years) received a single oral dose of enzalutamide (160 mg) under fasting conditions on day 1 and were followed for 50 days. Pharmacokinetic profiles were obtained for enzalutamide and its major metabolites, carboxylic acid metabolite (M1; inactive metabolite) and N-desmethyl enzalutamide (M2; active metabolite), on day 1 up to 1176 hours (49 days). Safety data were also collected.

FINDINGS: Enzalutamide plasma concentration rapidly increased (median Tmax , 1.5 hours) followed by a slow decrease (mean t½ , 90.7 hours). M1 and M2 plasma concentrations increased gradually with a median Tmax of 72.0 and 121 hours, respectively. M1 and M2 mean metabolite-to-parent ratios were 0.2 and 1.3, respectively. Mean AUC0-∞ of enzalutamide plus M2 was 828 μg h/mL versus 368 μg h/mL for enzalutamide alone. Mean t½ , maximum concentration, and Tmax of enzalutamide plus M2 were comparable with those of enzalutamide. Drug-related treatment-emergent adverse events were reported in 4 men (28.6%): 1 each of upper respiratory tract infection, chest discomfort, increased blood bilirubin, and decreased white blood cell count. No deaths or serious treatment-emergent adverse events were observed.

IMPLICATIONS: The pharmacokinetic profiles of enzalutamide, M1, M2, and enzalutamide plus M2 in healthy Chinese men were generally consistent with those in white men. No new safety concerns were found. Chinese Clinical Trial Registration identifier: CTR20150635.