Significant survival benefit seen in phase III study of prostate cancer agent

Administration of sipuleucel-T (Provenge) in men with advanced androgen-independent prostate cancer shows a significant survival benefit and "a very favorable toxicity and safety profile," according to the authors of a double-blind, placebo-controlled, multicenter phase III study published recently in the Journal of Clinical Oncology (2006; 24:3089-94).

Sipuleucel-T is an investigational cellular immunotherapeutic agent that targets prostatic acid phosphatase, an antigen present in 95% of prostate cancers.

In the randomized study, 127 men with asymptomatic, metastatic, androgen-independent prostate cancer who were given three infusions of sipuleucel-T every 2 weeks for 1 month had a median survival time that was 4.5 months longer than that of men who received placebo. Among men in the treatment group, there was a 41% overall reduction in risk of death (p=.010; HR=1.7). One-third (34%) of those who received the drug were alive 36 months after treatment, compared with 11% of men who received placebo, reported lead author Eric J. Small, MD, of the University of California, San Francisco.

In addition, those who received sipuleucel-T had a 31% delay in time to progression compared with those who received placebo, although this improvement did not achieve statistical significance (p=.052; HR=1.45). Men in the treatment arm experienced an eight-fold increase in post-treatment T-cell immunity compared with men in the placebo group (p<.001). The agent was well tolerated; the most common side effect was transient infusion-related low-grade fever and chills.

"This trial is an important milestone in the development of new treatments for prostate cancer patients," Dr. Small said. "The survival benefit that was observed has the potential to offer important benefits to patients, and represents the first time an immunotherapy has provided a survival advantage in prostate cancer."

The drug's manufacturer, Dendreon Corp., said it plans to submit a biologics license application to the FDA in late 2006.