PROSTVAC Phase 3 Clinical Study

PROSPECT is a global, randomized, double-blind, placebo-controlled phase 3 study being conducted under a Special Protocol Assessment (SPA) from the FDA. The objective of the study is to determine whether PROSTVAC® alone or in combination with GM-CSF is effective in prolonging overall survival in men with few or no symptoms from metastatic, castration-resistant prostate cancer (mCRPC). 

By January 2015, the study had been fully enrolled with 1,297 asymptomatic or minimally symptomatic mCRPC patients. Patients were enrolled at more than 200 sites in 15 countries, including Australia, Belgium, Canada, Denmark, Estonia, France, Germany, Iceland, Israel, Netherlands, Poland, Russia, Spain, United Kingdom and the United States.

Study design

Men with non/minimally symptomatic mCRPC (n=1297)  PROSTVAC  Long-term follow up  SURVIVAL 

5 Months Treatment

Interim analysis plan

Although the trial is powered to detect a difference in survival between active treatment and placebo at final analysis, three pre-specified interim analyses of data have been integrated into the statistical plan to evaluate whether the trial should continue as planned or potentially be stopped early for efficacy or futility. These interim analyses will occur after a certain number of events (deaths) have occurred in both comparisons of treatment arms versus placebo.

The first interim analysis took place in February 2016 based upon the occurrence of 214 events, and the second interim analysis took place in July 2016 based upon the occurrence of 321 events. Both analyses confirmed that the study will continue as planned. While the final study data are anticipated in 2017 and requires 534 events in both comparisons, a third interim analysis will occur at 427 events. Should the PROSPECT trial prove successful, applications for approval will be made in the United States, the European Union and other territories.

Additional details of the study can be found on