Provenge is designed to stimulate a patient's immune system against prostate cancer. A midstage trial of the vaccine in 127 patients with late-stage prostate cancer failed to reach its stated goal of slowing the disease's spread, usually a death knell for a new drug facing the FDA (see BusinessWeek, 4/30/07, "Teaching The Body To Fix Itself"). But when Dendreon dug into the data it discovered patients on Provenge lived an average of 4 1/2 months longer than those receiving the standard chemotherapy, Taxotere.
But since the trial wasn't meant to prove survival, it was possible something else could be prolonging these patients' lives. The trial wasn't well-designed, "so it leaves plenty of ambiguities," according to Dr. Howard I. Scher, an expert in prostate cancer at Memorial Sloan-Kettering Cancer Center in New York. "It doesn't mean the drug isn't working, but it needs more study."