Sipuleucel‐T is an investigational active cellular immunotherapy product designed to stimulate an immune response against prostate cancer. The safety and efficacy of sipuleucel‐T was evaluated in 2 identically designed, randomized, double‐blind, placebo‐controlled trials (D9901 and D9902A) conducted in men with advanced prostate cancer.

A total of 225 patients were randomized in D9901 or D9902A to sipuleucel‐T (n = 147) or placebo (n = 78), given as 3 intravenous infusions approximately 2 weeks apart. Patients were followed for survival until death or a prespecified cutoff of 36 months after randomization.

In the integrated analysis of D9901 and D9902A, patients randomized to sipuleucel‐T demonstrated a 33% reduction in the risk of death (hazard ratio, 1.50; 95% confidence interval, 1.10‐2.05; P = .011; log‐rank). The treatment effect remained strong after performing adjustments for imbalances in baseline prognostic factors, poststudy treatment chemotherapy use, and non–prostate cancer‐related deaths. Additional support for the activity of sipuleucel‐T is provided by the correlation between a measure of the product's potency, CD54 up‐regulation, and overall survival. The most common adverse events associated with treatment were chills, pyrexia, headache, asthenia, dyspnea, vomiting, and tremor. These events were primarily grade 1 and 2, with durations of 1 to 2 days.

The integrated results of D9901 and D9902A demonstrate a survival benefit for patients treated with sipuleucel‐T compared with those treated with placebo. The generally modest toxicity profile, coupled with the survival benefit, suggests a favorable risk‐benefit ratio for sipuleucel‐T in patients with advanced prostate cancer. Cancer 2009. © 2009 American Cancer Society.