Enzalutamide in the Context of Nonmetastatic CRPC

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Judd W. Moul, MD: Enzalutamide is also being studied intently in M0 CRPC. The trial that was recently completed is called the PROSPER trial, and that was a large phase III randomized trial looking at men with this nonmetastatic castration-resistant prostate cancer, randomizing those men 2-to-1 to the oral antiandrogen enzalutamide versus placebo. We don’t know the official results of the trial, but in mid-September 2017, Pfizer, which now owns the rights to the drug, reported in a press release that enzalutamide met the criteria for success and they would be submitting an application to the FDA for expansion of the label.

Remember, enzalutamide has been FDA approved for a number of years to treat metastatic castrate-resistant prostate cancer, but the current label does not include M0 CRPC. What I don’t know is this: Will the FDA act more quickly on this request for label expansion and open the doors to using it in M0 prostate cancer fairly soon? As of late 2017, as we’re talking now, enzalutamide is not yet FDA approved for M0 CRPC.

Charles J. Ryan, MD: Enzalutamide is an FDA-approved orally available therapy that has been approved in 2 contexts for metastatic castration-resistant prostate cancer. One indication is in patients with metastatic disease who have progressed after docetaxel chemotherapy. And in the other setting, it’s approved for patients who have asymptomatic or minimally symptomatic metastatic castration-resistant disease. In both settings, in studies in both of those contexts, enzalutamide demonstrated a significant improvement in progression-free survival compared to a placebo. It also demonstrated a significant improvement compared to placebo in overall survival.

It’s a well-tolerated orally available therapy. Many patients are able to take it without significant problems for months or even years. As we’ve been able to give more and more of it, there have been a few toxicities that have emerged that are of concern. One is cognitive changes that can occur in patients. Fatigue and even falls have been reported related to this drug. So, that is something that’s being explored and is probably affecting a subset of the patients. My own personal feeling is that this might be more of an effect on elderly patients as opposed to younger patients.

Transcript Edited for Clarity