Provenge Prostate Cancer Vaccine passes FDA milestone

The Food and Drug Administration approved the first therapeutic cancer vaccine in mid 2010. Sipuleucel-T, known by the trade name Provenge, was developed by Dendreon, a company based in Seattle, Washington, and has shown in clinical trials to improve median survival by more than four months in men with metastatic prostate cancer that has become resistant to hormone therapy. Is it a true vaccine? It is a "novel immunotherapeutic cellular product" and could essentially function as a vaccine for prostate cancer. It has been tried on men with androgen-dependent biochemically relapsed prostate cancer and found to be effective enough to gain regulatory approval.

The vaccine works by boosting the body’s immune system to generate an attack on the cancer cells. What is unique about Sipuleucel-T is that it is customized for each patient. A sample of the patient’s blood is taken and the antigen-presenting cells (APC’s) are isolated. These cells are sent to the manufacturer where they are cultured with a proprietary protein and sent back as a supercharged immune system boosting vaccine that is then injected into the patient. This process is done three times over the four-to-six week course of treatment.

The FDA was resistant in the past to approve the drug because while it does improve survival, it does not completely stop the cancer from growing. The vaccine only boosts the immune system in a way that makes it much more difficult for the tumor to grow. This slows down the tumor’s progression, but does not stop it completely.

Initially, availability of the vaccine will be an issue. Currently, there is only one manufacturing facility approved to make it, with two others pending approval by the FDA. Demand will certainly exceed supply until at least mid-2011. Since immunotherapy treatment for cancer is such a new field, another challenge is determining the point at which treatment should move on to something else like the chemotherapy drug docetaxel. This was not determined before trials began. Variations in the path of treatment after administration of sepuleucel-T can cloud the results.

An exciting next step is the beginning of trials on men with prostate cancer in the earlier stages, which may turn out to be the most beneficial time for this immunotherapy, according to researchers. In the earlier stages, immunotherapy can be used in combination with other treatments, possibly producing a cumulative positive effect.

Provenge will be delivered intraveneously, probably over a one-month period.