A vaccine designed to treat advanced prostate cancer that doesn't respond to hormone therapy was ruled safe and effective by an FDA advisory panel last spring. But in an unusual move, the FDA has delayed approval until the manufacturer, Dendreon Corporation, completes a study to measure overall survival. The company anticipates that interim survival results will be available in 2008.

The vaccine, sipuleucel-T (Provenge), is the first of a new class of drugs that stimulates the immune system to kill cancer cells. It contains a protein found in most prostate cancers and an agent that helps disease-fighting cells recognize the cancer cells as a threat. If approved, it would be the first therapeutic vaccine marketed for cancer. Previously approved vaccines for liver and cervical cancers are solely preventive.

Studies of Provenge indicate that it could lengthen the lives of patients with advanced prostate cancer by 41/2 months, compared with those who receive a placebo. Only one other prostate cancer drug, docetaxel, has been shown to prolong life, but it has many adverse effects. Adverse reactions to Provenge, such as infusion-related fever and chills, were generally mild and self-limiting.

For more information, visit http://www.dendreon.com.