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.

Based on the dosing schedule of PROSTVAC, all men would have completed their course of therapy no later than June 2015. 

Study design

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

5 Months Treatment

Interim analysis plan

The PROSPECT trial is designed to detect a difference in survival between active treatment and placebo at final analysis, which will occur at 534 events (deaths) in each comparison of the two treatment arms versus placebo. However, 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.

The efficacy and futility hurdles for these interim analysis are, what the Company considers to be, high, and it is the Company’s continued belief that the study will continue to the final OS analysis. The first two interim analyses occurred at 214 and 321 events respectively, both confirming that the study should continue without modification as recommended by the  independent Data Monitoring Committee (DMC). The results of the third interim analysis (427 events) will be reviewed by an independent Data Monitoring Committee (DMC) and the DMC plans to convene for this analysis in September 2017. Final results are expected in the fourth quarter of 2017. The Company remains blinded to all data.

Additional details of the study can be found on