Safety and effectiveness of enzalutamide in men with metastatic, castration-resistant prostate cancer

Introduction: Enzalutamide (MDV3100) is a second-generation androgen receptor antagonist that improves survival in metastatic, castration-resistant prostate cancer (mCRPC). Alternatives include chemotherapy, radiation, immunotherapy and abiraterone. Areas covered: The Phase I/II study showed early evidence of efficacy and determined that fatigue is the dose-limiting toxicity. Two randomized, placebo-controlled trials have demonstrated superiority of enzalutamide 160 mg by mouth daily over placebo in terms of overall survival, radiographic progression-free survival as well as a broad range of secondary and exploratory end points in men who had received previous chemotherapy (AFFIRM) and in those who were chemotherapy naive (PREVAIL). Common side effects include fatigue, arthralgias and constipation. A post hoc analysis from AFFIRM found that enzalutamide is safe and effective in men aged ≥ 75 years. The Phase I/II studies as well as AFFIRM and PREVAIL are described in this review. Expert opinion: Enzalutamide extends overall and progression-free survival and is associated with robust response rates and quality of life benefits in men with mCRPC. Enzalutamide has not been proven to be effective in biochemically relapsed disease or in castration-sensitive prostate cancer. It should not be used in men at high risk for seizure, and patients should be counseled about the increased risk of falls.