Immunotherapy is cancer treatment designed to stimulate the immune system, the body's natural mechanism for fighting disease, in the hope that it may overcome many of the limitations of traditional cancer therapies such as surgery, radiation, chemotherapy and hormone treatments. A person's immune system is composed of a variety of specialized cells that recognize foreign antigens, the chemical structures that are found on disease-causing agents. In a healthy body, the immune system will treat the agent carrying the unfamiliar antigen as a foreign invader and fight to remove it from the body.

Tumors, however, frequently display characteristics of antigens that are also found on normal cells, perhaps making it difficult for the immune system to distinguish between them and mount a strong anti-cancer response. Tumors may also actively prevent the immune system from working correctly.

Researchers believe that one key to directing the immune system to fight cancers is to modify, or engineer, tumor antigens so that the immune system can recognize and destroy cancer cells. The modified antigen is combined in the laboratory with antigen presenting cells taken from a cancer patient, which then activates the cells. The activated cells are re-administered to the patient to stimulate their T-cells to recognize and attack cancer cells that carry the target antigen.

Provenge® (also known as sipuleucel-T)
Provenge is an investigational product that may represent the first in a new class of active cellular immunotherapies (ACIs) that are uniquely designed to stimulate a patient's own immune system. ACIs hold promise because they may provide patients with a meaningful survival benefit with low toxicity. Provenge targets the prostate cancer antigen, prostatic acid phosphatase (PAP), which is found in approximately 95% of prostate cancers. Provenge is in late-stage clinical development for the 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.

Cell Genesys GVAX® immunotherapy for prostate cancer is a non patient-specific product comprised of two genetically-modified prostate cancer cell lines. Cell Genesys intends to develop and manufacture this immunotherapy as an "off-the-shelf" pharmaceutical for use after hormonal therapy for advanced-stage prostate cancer.

Source: Prostate Health Education Network website. www.prostatehealthed.org