Dendreon's prostate cancer vaccine significantly prolonged the overall survival among 500 men with advanced, metastic prostate cancer compared to a placebo, the company said Tuesday.
Results were "robust" and "unambiguous," a spokesman said during today's (Tues April 14) company broadcast conference call with biotech investment analysts.
"The successful outcome from the Phase 3 IMPACT study provides validation of the long-pursued goal of harnessing the human immune system against a patient's own cancer," Dendreon Chief Executive Mitchell Gold said in a statement.
"Survival is the gold standard outcome for oncology clinical trials, and overall survival was the primary endpoint of the IMPACT trial. The positive results from this landmark study provide confirmatory evidence demonstrating that treatment with PROVENGE may prolong survival," Dendreon CEO Mitch Gold said.
The Seattle-based drugmaker said the phase III study of Provenge, known as IMPACT, met its primary endpoint with statistical significance. Details of the study are being withheld so that they can be presented at the American Urological Association's Annual Meeting in Chicago on April 28.
The company said the successful trial means Provenge may represent the first in a new class of active cellular immunotherapies designed to engage the patient's own immune system against cancer. Because the data meet the criteria and specifications outlined in Dendreon's Special Protocol Assessment (SPA) agreement with the U.S. Food and Drug Administration, the company intends to move forward in the fourth quarter of this year to gain licensure of Provenge.
The IMPACT study enrolled 512 men with advanced prostate cancer who no longer responded to hormone therapy. The primary endpoint of the study was to determine if treatment with Provenge prolonged overall survival of patients compared to a placebo.
Provenge is a cancer immunotherapy designed to prime a patient's immune system to zero in on prostate cancer cells by recognizing Prostatic Acid Phosphatase (PAP). Normally produced in trace amounts by the healthy prostate, PAP levels shoot up in men with active prostate cancer as the cancer cells start churning it out. The highest levels of acid phosphatase are found in metastasized prostate cancer. Provenge trains T-cells in the immune system to recognize PAP as foreign and attack.
In March 2007, and advisory committee of outside experts convened by the FDA recommended the approval of Provenge as a treatment for prostate cancer based on clinical data from a prior phase III study. But in May of that year, the FDA rejected the panel's recommendation and refused to approve Provenge until additional survival data could be compiled from the IMPACT study.
Data on overall survival is key to finding out whether therapies actually extend lives rather than merely lowering symptoms or treating one disease and causing speedier death from other causes.
Everything now depends on the data to be presented during a plenary session at the AUA meeting in Chicago on Tues., Apr. 28 and on FDA's final approval process.
LINKS
Press release Tue April 14 2009 PROVENGE Significantly Prolongs Survival in Men with Advanced Prostate Cancer in Pivotal Phase 3 IMPACT Study
Dendreon Conference Call with investment analyists -- listen online 
Dendreon Wins | Forbes April 14, 2009
A victory for the company's controversial prostate cancer treatment, but more debate lies ahead.
Wall Street Journal | APRIL 14, 2009, 12:57 P.M. ET Dendreon Says Prostate-Cancer Treatment Prolonged Survival; Shares Surge
FDA PROVENGE HEARING 2007 -- Testimony from Prostate Cancer Patients & Caregivers