Overall survival and rPFS data from the PREVAIL trial expected later this year

According to a media release issued by Astellas Pharma and Medivation, the companies now expect to conduct an interim analysis of the PREVAIL trial of enzalutamide (a.k.a. MDV3100 or Xtandi) for overall survival some time later this year.

The PREVAIL study is an international, multi-center, randomized, plaecebo-controlled Phase III trial of enzalutamide versus a placebo in men withe chemotherapy-naive, metastatic, castration-resistant prostate cancer (mCRPC). It was initiated in late 2010.

In the media release issued earlier today, the companies stated the following key points:

  • The trial enrolled 1,717 patients who had progressed on treatment with either an LHRH receptor analog alone or an LHRH receptor analog and an antiandrogen (such as bicalutamide or flutamide).
  • The trial has co-primary endpoints of overall survival and radographic progression-free survival (rPFS).
  • The trial was fully enrolled as of May 2012.
  • The protocol-specified number of rPFS events has already been exceeded.
  • The primary analysis of the rPFS data will occur at the same time as the interim analysis for overall survival.

What this means if that although the company could, in fact, stop this trial now and analyze the available data for the effect of enzalutamide compared to a placebo on rPFS, they want to follow the trial long enough to be able to establish a true overall survival benefit for enzalutamide in men with chemotherapy-naive mCRPC.

Readers may be aware that the developers of abiraterone acetate (Zytiga) stopped their comparable trial in men with chemotherapy-naive mCSPC early and announced results only on the basis only of rPFS. WE do not know the impact of abiraterone acetate + prednisone on the overall survival of this group of patients compared to a placebo + prednisone.

It is not clear from the media release exactly when in 2013 that Astellas and Medivation will be able t0 conduct this interim analysis and report the available data. We can be reasonably confident that it will not occur in time for presentation at ASCO (which in now just a month away). It seems much more likely that we are looking at a date nearer to the end of the year.

Quoted in the media release, the chief medical officer of Medivation stated only that, “We’ve shared our updated plan with the U.S. Food and Drug Administration who are in agreement with our approach. We plan to conduct the PREVAIL interim analysis in 2013.”

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