Dr. Charles G. Drake of New York-Presbyterian/ Columbia University Medical Center spoke with Prostatepedia about new prostate cancer vaccines under investigation.
Dr. Charles Drake: Hopefully before the end of the year, a trial called PROSPECT will read out. (Though it’s hard to tell nowadays when trials are going to read out because we already have a reasonable number of options: six FDA-approved drugs for men with metastatic castration-resistant disease.) PROSPECT is an international randomized Phase III trial of about 1,200 men that looks at Prostvac, an off-the-shelf PSA-targeted vaccine. The trial’s primary endpoint is overall survival.
Unlike the Provenge (sipuleucel-T) trials, which were sometimes a little complicated to interpret because we had crossover, patients on PROSPECT didn’t crossover. That means that patients on the placebo arm who progressed were not eligible for Prostvac, instead, they went on to standard treatments. The lack of crossover means we expect a fairly clean set of survival data to come out from this large PROSPECT trial. There are a lot of folks in the prostate cancer community looking forward to seeing whether or not PROSPECT will have a survival benefit.
So then we’d have two vaccines for prostate cancer?
Dr. Drake: Provenge (sipuleucel-T) is an active drug with clear utility. The challenge with Provenge (sipuleucel-T) is that patients need to undergo leukapheresis to prepare this personalized vaccine. Prostvac is more like the vaccinia vaccine that was used for smallpox. It will be a bit easier to distribute widely.
Is inconvenience the only factor limiting Provenge (sipuleucel-T) use?
Dr. Drake: The prostate cancer field is like all other fields in that we tend to be trendy at times. When Provenge (sipuleucel-T) was first approved, there was a ton of enthusiasm about it and lots of people were using it. In fact, there was a bit of controversy over whether or not we could make enough of it.
With all the new drugs coming out, Provenge (sipuleucel-T) is probably used less than it once was. But this is something that has been FDA approved and has a clear survival benefit.