Last week the US Food and Drug Administration approved Provenge (sipuleucel-T), an autologous cellular immunotherapy for treating advanced prostate cancer, developed by the biotechnology company Dendreon (Seattle). If commercially successful, the approval of this cancer immunotherapy, a cancer vaccine, which uses a patient’s own immune system to combat the disease, may offer a new treatment paradigm for cancer. Key questions going forward, however, are how the product will fare commercially against existing anticancer therapies and the long-term financial viability of producing a personalized medicine.

Provenge is an autologous cellular immunotherapy indicated for treating asymptomatic or minimally symptomatic metastatic, castrate resistant (hormone-refractory) prostate cancer. Provenge is designed to induce an immune response against prostatic acid phosphatase, an antigen expressed in most prostate cancers, according to a company press release. Dendreon intends to make Provenge available through approximately 50 centers, all of which were approved clinical-trial sites for the product, and expects to increase capacity over the next year. The increased capacity will be a result of the anticipated licensure of expanded facilities in New Jersey, Atlanta, and Orange County, California, in mid-2011, according to the company release.

For producing Provenge and other immunotherapies, Dendreon relies on techniques in processing antigen-presenting cells and identifying and engineering antigens. The company’s Antigen Delivery Cassette technology is designed to enhance antigen binding and entry into antigen-presenting cells. The Antigen Delivery Cassette targets each engineered antigen to a receptor on antigen-presenting cells and provides a common key to unlock the potential of these cells to process antigen. The antigen-presenting cells process antigen along pathways that stimulate cell-mediated immunity, according to the company.

The company’s manufacturing process for immunotherapy products incorporates two elements: the fusion protein created using the Antigen Delivery Cassette technology and antigen-presenting cells. To obtain antigen-presenting cells, the company arranges to have white blood cells removed from a patient through a standard blood-collection process called leukapheresis. Antigen-presenting cells are collected using the company’s proprietary cell-separation technology. These antigen-presenting cells are incubated with the required concentration of the engineered protein under controlled conditions. In general, after approximately 40 hours, the antigen-presenting cells are ready to be used. Each dose is subject to quality-control testing, including identity, purity, potency, sterility, and other safety testing. In general, the process requires less than three days from white-blood-cell collection to the administration of the active immunotherapy product candidate.

FDA approval of Provenge is a significant milestone in meeting the clinical, quality, and supply requirements for producing an immunotherapy. It will be important to observe the commercial and clinical success of the product to consider the potential of other immunotherapy products as possible approaches for treating cancer.