Progression-free survival (PFS) is not improved in patients with metastatic castration-resistant prostate cancer (mCRPC) when enzalutamide is added to abiraterone acetate with prednisone, compared with abiraterone with prednisone alone, according to findings from a new trial.
The US Food and Drug Administration (FDA) initially approved enzalutamide, an androgen receptor inhibitor, in 2012 as a treatment option for patients with mCRPC previously treated with docetaxel and hormonal therapy. After further trials validated survival outcomes for patients treated with the drug, the FDA expanded approval for enzalutamide to treat men with chemotherapy-naïve mCRPC. Similarly, the FDA granted approval for abiraterone in 2011 as a treatment option for patients with mCRPC previously treated with docetaxel, and their approval was expanded in 2012 to include men with chemotherapy-naïve mCRPC.
In a randomized, placebo-controlled, phase IV study, researchers from Medivation, Inc, a subsidiary of Pfizer, compared the effects of enzalutamide with the combination therapy abiraterone and prednisone to abiraterone and prednisone alone for men with mCRPC who were chemotherapy-naïve and had progressed on single-agent enzalutamide. Researchers subjected 509 chemotherapy-naïve patients with mCRPC to initial treatment with enzalutamide (160 mg/day) until their prostate-specific antigen level increased, followed by a randomized treatment course of either enzalutamide (160 mg/day) plus abiraterone (1000 mg/day) and prednisone (10 mg/day) or placebo plus abiraterone and prednisone at the same doses. The primary outcome was PFS.
Topline results from the study showed that enzalutamide failed to improve PFS in the patients evaluated. Full results of the study have not yet been released. Nonetheless, the researchers contend that studies such as the one they have conducted are essential to furthering treatment advances of mCRPC.
“It is critical that we continue to focus on addressing the unmet needs of men with metastatic CRPC, who have a poor prognosis despite treatment advances,” said Mohammad Hirmand, MD, Interim Chief Medical Officer at Medivation. “We will continue to analyze these data to better understand the results with the goal of further helping these patients.”
