Efficacy and Safety of Enzalutamide in a Real-World Cohort of Japanese Patients With Castration-resistant Prostate Cancer.

BACKGROUND/AIM: It has been reported that some adverse events (AEs) of enzalutamide (ENZ) occur more frequently in Japanese patients with castration-resistant prostate cancer (CRPC) due to higher steady-state trough plasma concentrations of ENZ (CSS, ENZ) and its active metabolite (NDE), (CSS, NDE). Thus, we investigated the efficacy, safety, and pharmacokinetics of ENZ in Japanese patients with CRPC. PATIENTS AND METHODS: Fourteen patients were administered ENZ at a standard dose (160 mg/day) or reduced doses (80 or 120 mg/day). Prostate-specific antigen (PSA), AEs, CSS, ENZ, and CSS, NDE were examined. RESULTS: A maximum PSA decrement of ≥50% from baseline was achieved in 92% of patients. AEs were few (>20%) and mild. No differences in CSS, ENZ and CSS, NDE between other ethnic groups in previous literature and our subjects was observed. CONCLUSION: ENZ shows adequate efficacy and safety in Japanese patients with CRPC, even if administered at reduced doses in real-world conditions.