This is an extremely important study,” said Daniel Petrylak, MD, Professor of Medicine and Urology at the Yale School of Medicine in New Haven, Connecticut. “This work needs to be replicated prospectively in a larger group of patients. Right now we have no way to select appropriate first-line therapy for these patients other than clinical parameters,” Dr. Petrylak continued.

“None of the patients with the AR-V7 variant responded to enzalutamide. This blood test, if replicated, will give us a way to differentiate patients for therapy.”

Possible FDA Approval

Dr. Petrylak said that enzalutamide may be approved by the U.S. Food and Drug Administration (FDA) within the next year for the prechemotherapy setting based on results of the PREVAIL trial, which means that the clinician would have four options for treatment in this clinical state (including abiraterone [Zytiga]/prednisone, radium-223 [Xofigo], and sipuleucel-T [Provenge]) in addition to enzalutamide (Xtandi).

“Although the data will not help select for the latter three agents, it would seem as if a positive AR-V7 test would exclude enzalutamide as a therapeutic option. This has the potential to save resources and prevent delay of other therapies, which are potentially more effective. It makes no sense to give a drug that you know is not going to work,” Dr. Petrylak commented.

Dr. Petrylak said there are several hurdles to obtaining approval for this test, but if approved, “it will be very useful.” This study is a first step. ■

Disclosure: Dr. Petrylak reported no potential conflicts of interest.