Sipuleucel-T, an active cellular immunotherapy agent, improves survival in men with asymptomatic, metastatic androgen-independent prostate cancer, according to a presentation at the ECCO 13-European Cancer Conference. The results come from a second phase III study.

"The combined data from the trials of PROVENGE (sipuleucel-T) versus placebo demonstrate that active immunotherapy favorably impacts survival in men with asymptomatic, metastatic, androgen-independent prostate cancer," reported Celestia S. Higano, MD, director and associate professor of the Genitourinary Oncology Clinical Research Group at the University of Washington, Seattle, who presented the data.

"Given the favorable side effect profile, sipuleucel-T may provide a useful alternative for men prior to initiating chemotherapy."

In the current study, the three-year final survival analysis of 98 men with asymptomatic, metastatic, androgen-independent (hormone- refractory) prostate cancer showed that sipuleucel-T patients had a 19.0 month median survival compared with only 15.7 months for placebo patients. This represents a 3.3-month or 21-percent improvement in median survival.

A Cox multivariate regression analysis of overall survival, which adjusts for imbalances in prognostic factors known to influence survival, met the criteria for statistical significance. The hazard ratio observed in this analysis was consistent with that seen in the Company's first Phase 3 study. In addition, at the three- year final follow up, 32 percent of men in the sipuleucel-T group were alive compared with only 21 percent of placebo group patients, a 52-percent improvement in survival rate.

As in previous studies, the investigational agent was well tolerated with the most common adverse events reported being fever and chills lasting for one to two days.
At the conference, Higano also presented an integrated analysis of data from both phase III studies, which showed a statistically significant survival benefit in the overall intent-to-treat population of 225 patients. In this analysis, sipuleucel-T patients had a median survival of 23.2 months compared with 18.9 months for patients in the placebo group, a 4.3-month or 23-percent improvement in median survival.

In addition, at the three-year final follow-up, 33 percent of men who received sipuleucel-T were alive compared with 15 percent of men who received placebo, a greater than 100-percent improvement.

Sipuleucel-T is an investigational product that may represent the first in a new class of active cellular immunotherapy’s that are uniquely designed to stimulate a patient's own immune system. Such agents hold promise because they may provide patients with a meaningful survival benefit with low toxicities. Sipuleucel-T targets the prostate cancer antigen, prostatic acid phosphatase, which is found in approximately 95 percent of prostate cancers.

The agent is in late-stage clinical development for treatment of patients with early-stage and advanced prostate cancer. In clinical studies, patients typically received three infusions over a one-month period as a complete course of therapy.