The US Food and Drug Administration (FDA) has approved enzalutamide (Xtandi, Astellas/Pfizer) for the treatment of men with castration-resistant prostate cancer (CRPC), according to a joint company press statement. The approval extends the indication for the oral therapy, which was previously approved for men with metastatic CRPC

Enzalutamide becomes the second androgen receptor-targeting therapy to be approved for use in this earlier setting. Apalutamide (Erleada, Janssen) was similarly approved in February.

"With today's approval, there is now a new option for men with non-metastatic CRPC, who are in between the failure of androgen deprivation therapy resulting in CRPC and the onset of metastatic disease," said Jonathan Simons, MD, president of the Prostate Cancer Foundation, in the joint company press statement.

Comparision between enzalutamide plus androgen deprivation therapy and  ADT plus placebo

The extended indication is based on results from the PROSPER trial, in which enzalutamide plus androgen deprivation therapy (ADT) was compared with ADT plus placebo.

In the 1401-patient trial, enzalutamide decreased the risk for distant metastasis or death by 71% (hazard ratio, 0.29; 95% confidence interval, 0.24 – 0.35; P < .0001), with a median metastasis-free survival of 36.6 vs 14.7 months in the placebo group (an improvement of 21.9 months).

The most common adverse reactions (≥ 10%) that occurred more frequently in the enzalutamide arm compared with the placebo arm were asthenic conditions (40% vs 20%), hot flush (13% vs 7.7%), hypertension (12% vs 5.2%), dizziness (12% vs 5.2%), nausea (11% vs 8.6%), and fall (11% vs 4.1%). Overall, adverse events were higher in the enzalutamide arm than in the placebo arm (any grade: 87% vs 77%; grades ≥ 3: 31% vs 23%).

Also, 3.4% of patients in the enzalutamide arm and 0.6% in the ADT-alone arm died from adverse events. Discontinuations with an adverse event as the primary reason were reported for 9.4% of patients in the enzalutamide arm vs 6% in the placebo arm.

Data from the PROSPER study were first presented at the 2018 Genitourinary Cancers Symposium (ASCO GU) in February, as reported by Medscape Medical News.