This post hoc analysis evaluated treatment effects, safety, and pharmacokinetics of enzalutamide in Korean patients in the phase 3, double-blind, placebo-controlled PREVAIL trial.
Asymptomatic or mildly symptomatic chemotherapy-naive men with metastatic castration-resistant prostate cancer that progressed on androgen deprivation therapy received 160 mg/d oral enzalutamide or placebo (1:1) until death or discontinuation due to radiographic progression or skeletal-related event and initiation of subsequent therapy. Coprimary end points were centrally assessed radiographic progression-free survival (rPFS) and overall survival (OS). Secondary end points included investigator-assessed rPFS, time to initiation of chemotherapy, time to prostate-specific antigen (PSA) progression, PSA response (≥50% decline), and time to skeletal-related event.
Of 1,717 total patients, 78 patients were enrolled in Korea (enzalutamide, n=40; placebo, n=38). Hazard ratios (95% confidence interval) for enzalutamide versus placebo were 0.23 (0.02-2.24) for centrally assessed rPFS, 0.77 (0.28-2.15) for OS, 0.21 (0.08-0.51) for time to chemotherapy, and 0.31 (0.17-0.56) for time to PSA progression. A PSA response was observed in 70.0% of enzalutamide-treated and 10.5% of placebo-treated Korean patients. Adverse events of grade ≥3 occurred in 33% of enzalutamide-treated and 11% of placebo-treated Korean patients, with median treatment durations of 13.0 and 5.1 months, respectively. At 13 weeks, the plasma concentration of enzalutamide plus N-desmethyl enzalutamide was similar in Korean and non-Korean patients (geometric mean ratio, 1.04; 90% confidence interval, 0.97-1.10).
In Korean patients, treatment effects and safety of enzalutamide were consistent with those observed in the overall PREVAIL study population (ClinicalTrials.gov Identifier: NCT01212991).
Investigative and clinical urology. 2016 May 10 [Epub]
Choung-Soo Kim, Ad Theeuwes, Dong Deuk Kwon, Young Deuk Choi, Byung Ha Chung, Hyun Moo Lee, Kang Hyun Lee, Sang Eun Lee
Department of Urology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea., Biostatistics, Astellas Pharma Europe B.V., Leiden, The Netherlands., Department of Urology, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Gwangju, Korea., Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea., Department of Urology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea., Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea., Department of Urology, Center for Prostate Cancer, National Cancer Center, Goyang, Korea., Department of Urology, Seoul National University Bundang Hospital, Seongnam, Korea.