As part of a phase 3 trial, Howard I. Scher, M.D., from the Memorial Sloan-Kettering Cancer Center in New York City, and colleagues randomly assigned 1,199 men with castration-resistant prostate cancer after chemotherapy to receive placebo (399 patients) or 160 mg oral enzalutamide (targets multiple steps in the androgen-receptor-signaling pathway) per day (800 patients).

After an interim analysis performed after 520 deaths had occurred, the researchers stopped the study. The median overall survival for the enzalutamide group was significantly longer (18.4 versus 13.6 months; hazard ratio for death, 0.63). Enzalutamide treatment was also significantly better in terms of secondary end points, including the proportion of patients whose prostate-specific antigen levels fell by at least 50 percent, the soft-tissue response rate, the quality-of-life response rate, and time to the first skeletal-related event. The enzalutamide group had higher rates of fatigue, diarrhea, and hot flashes, and 0.6 percent of enzalutamide patients reported seizures.

"Enzalutamide significantly prolonged the survival of men with metastatic castration-resistant prostate cancer after chemotherapy," Scher and colleagues conclude.

The study was funded by Medivation and Astellas Pharma Global Development, the developers of enzalutamide; several authors disclosed financial ties to pharmaceutical and biotechnology companies, including Medivation and Astellas.

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