Enzalutamide Approved for Late-Stage Prostate Cancer

Howard Scher, MD

The FDA has approved enzalutamide (Xtandi) for use in patients with metastatic castration-resistant prostate cancer (mCRPC) who have been previously treated with docetaxel and hormonal therapy.

Enzalutamide was reviewed through the FDA’s priority review program. The federal agency approved the drug nearly a full three months before the original action date of November 22, 2012.

"Enzalutamide provides an exciting new option for physicians that can prolong the lives of patients with metastatic prostate cancer who have received chemotherapy," Howard I. Scher, MD, chief of the Genitourinary Oncology Service at Memorial-Sloan Kettering Cancer Center in New York, said in a statement.

The approval was based largely on data from the phase III AFFIRM study published in the New England Journal of Medicine earlier this month. In that study, 1199 men were randomized in a 2:1 ratio to receive either once-daily, oral enzalutamide monotherapy or placebo. Patients in the enzalutamide arm of the study had a median overall survival of 18.4 months (95% confidence interval [CI], 17.3 to not yet reached), compared to 13.6 months in the placebo arm (95% CI, 11.3 -15.8; hazard ratio = 0.63; 95% CI, 0.53-0.75; P < .0001).

Richard Pazdur, MD

In the study, men in the enzalutamide group had higher rates of fatigue, diarrhea, joint pain, and other side effects. Additionally, seizures were reported in five patients receiving enzalutamide. However, the time to the first serious adverse events was extended in the experimental arm, when compared to the placebo.

“The need for additional treatment options for advanced prostate cancer continues to be important for patients,” said Richard Pazdur, MD, director of the Office of Hematology and Oncology Products in FDA’s Center for Drug Evaluation and Research, in a statement. “Xtandi is the latest treatment for this disease to demonstrate its ability to extend a patient’s life.”

An additional study was required by the FDA to further assess the safety profile of enzalutamide, specifically in men who are at high risk for seizure.

Scher HI, Fizazi K, Saad F, et al. Increased Survival with Enzalutamide in Prostate Cancer after Chemotherapy [Published online ahead of print August 15, 2012]. N Engl J Med. 2012. DOI: 10.1056/NEJMoa1207506.