Enzalutamide Granted Priority Review for Expanded Use in Prostate Cancer

Clinicians soon may have a new treatment option to offer men with nonmetastatic castration-resistant prostate cancer (CRPC). The US Food and Drug Administration (FDA) is granting Priority Review for a supplemental new drug application for enzalutamide (XTANDI) in nonmetastatic CRPC. This androgen receptor inhibitor is currently approved for men with metastatic CRPC.

There is a great unmet need to delay development of metastases in this patient population, according to the researchers. Under Priority Review, the FDA is expected to take action on an application within 6 months of receipt compared with 10 months under standard review.

The FDA approved enzalutamide in 2012 for the treatment of patients with metastatic CRPC who had previously received docetaxel. In 2014, the FDA approved it to treat all patients with metastatic CRPC. Mace Rothenberg, MD, chief development officer, oncology at Pfizer Global Product Development, said enzalutamide is already established as a standard of care for men with metastatic CRPC. However, this milestone marks an important step toward bringing this agent to CRPC patients in an earlier setting.

The FDA announcement comes on the heels of the latest results from the PROSPER trial, which evaluated enzalutamide plus androgen deprivation therapy (ADT) vs ADT alone in 1,401 men with nonmetastatic CRPC. The study showed that the use of enzalutamide plus ADT significantly reduced the risk of developing metastases or death by 71% compared with ADT alone. The median metastasis-free survival (MFS) was 36.6 months for men who received enzalutamide compared with 14.7 months with ADT alone.

“Preventing metastatic disease development is a big deal. The results of this trial showed more than 3 years of MFS compared to just over a year for standard ADT. The results of this trial are quite similar to the trial examining apalutamide in this clinical setting,” said Sam S. Chang, MD, endowed chair of urologic surgery and professor of urologic surgery and oncology at Vanderbilt University Medical Center in Nashville.

Adverse events in the PROSPER trial were generally consistent with those reported in prior enzalutamide clinical trials in patients with metastatic CRPC. The study showed that grade 3 or higher adverse event rates were higher in the enzalutamide arm (31% vs 23% for ADT alone). The most common (≥ 2%) grade 3 or higher adverse events were hypertension (5% vs 2% for ADT alone) and fatigue (3% vs 1% for ADT alone). Major adverse cardiovascular events were reported in 5% of patients in the enzalutamide arm compared with 3% in the ADT-only arm.

“The difficult part will be balancing the clear effectiveness of this agent with its side effects and cost in a population of men who do not have symptoms,” Chang told Cancer Network.