More data from the PREVAIL trial of enzalutamide

Data about the results of the Phase III PREVAIL trial of enzalutamide in men with chemotherapy-naive, metastatic, castration-resistant prostate cancer (mCRPC) continue to dribble out ahead of the formal presentation (which is to be given later this week at the Genitourinary Cancers Symposium in San Francisco).

We have previously provided the base information about the key results of the trial (see here). However, at a pre-meeting media briefing coordinated yesterday by the American Society of Clinical Oncology, the following additional information was also released:

  • The overall survival and radiographic progression-free survival benefits demonstrated by enzalutamide as compared to placebo therapy occurred even though 40 percent of enzalutamide patients and 70 percent of the placebo patients went on to receive subsequent therapies that can help to extend survival.
  • On average, patients taking enzalutamide went 17 months longer than those in the placebo group before requiring chemotherapy.

The prinicipal investigator for the PREVAIL trial, Dr. Tomaz Beer, is quoted as having said that these results tell us that “controlling the disease at this point in its course can have a long-term impact.”

Other results reported yesterday focused on the side effect profile of enzalutamide compared to placebo therapy in this trial:

  • Discontinuation rates due to side effects were about 6 percent in the enzalutamide patients and in the placebo patients.
  • Enzalutamide therapy appears to have induced hypertension in 13.4 percent of patients compared to 4.1 percent on placebo.
  • Serious cardiac events were reported in 2.8 percent of enzalutamide patients and in 2.1 percent of placebo patients.

Apparently, based on the results of the PREVAIL study, the drug’s developers are aiming to submit applications for approval of enzalutamide to treat men with chemotherapy-naive, mCRPC to the U.S. Food and Drug Administration and to the European Medicines Agency in “early 2014.”

Some industry analysts have started to suggest that the results of the PREVAIL trial may lead to enzalutamide use preferentially, prior to abiraterone acetate, in men with chemotherapy-naive mCRPC. For context on that opinion, it is worth remembering that the study of abiraterone acetate + prednisone compared to a placebo + prednisone in chemotherapy-naive mCRPC was stopped prior to evidence of any overall survival benefit, and that the radiographic progression-free survival benefit demonstrated by abiraterone + predisone was about 57 percent (as opposed to 81 percent for enzalutamide in the PREVAIL trial).

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