Prospect: A Randomized, Double-Blind, Phase Iii Efficacy Trial Of Prostvac.

TPS4699 Background: PROSTVAC is a candidate cancer vaccine comprised of two recombinant poxviral vectors: vaccinia (V) and fowlpox (F), each with insertions of four human genes: PSA and three costimulatory molecules (TRICOM) - LFA-3, B7.1 and ICAM-1. This off the shelf vaccine demonstrated a statistically significant overall survival (OS) benefit of 8.5 months while displaying a favorable side effect profile in patients (pts) with asymptomatic to minimally symptomatic prostate cancer (mCRPC) in a randomized, placebo –controlled 122-pt Phase II trial. Data from this Phase II trial supported the design of a Phase III protocol that will rigorously test the hypothesis of OS benefit, as well as expand our understanding of immune system response to cancer vaccines. Methods: 1200 pts will be randomized in a double-blind fashion to three arms: PROSTVAC, PROSTVAC+GM-CSF, or Placebo, at 1:1:1 ratio. A five-month treatment regimen will include a priming vaccination with PROSTVAC-V, and six booster vaccinations with ...