Sipuleucel-T in Metastatic Castration-Resistant Prostate Cancer†

Abstract

Sipuleucel-T is an autologous active cellular immunotherapy used in the treatment of men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (CRPC). It is the first therapeutic cancer vaccine to receive US FDA approval. Approximately 3 days prior to each infusion of sipuleucel-T, patients undergo a leukapheresis procedure for collection of autologous peripheral blood mononuclear cells. Preparation of sipuleucel-T involves enrichment for antigen-presenting cells from the leukapheresis product and activation ex vivo with a recombinant fusion protein (PA2024). In the randomized, double-blind, placebo-controlled IMPACT study in patients with metastatic CRPC, sipuleucel-T was associated with a 22% relative reduction in the risk of death (hazard ratio 0.78; p = 0.03), which was the primary endpoint of the trial. After a median follow-up period of 34.1 months, median survival was 4.1 months longer with sipuleucel-T than placebo (25.8 vs 21.7 months). There was no significant between-group difference for the median time to objective disease progression (a secondary endpoint). Almost all patients treated with sipuleucel-T in clinical trials reported an adverse event, although these were mild or moderate in severity (grade 1 or 2) in most patients. The most common adverse events (e.g. infusion-related events, such as chills and fever) generally occurred within the first day after administration of sipuleucel-T and resolved within 2 days.