Prostate cancer can be treated by immunotherapy, and it was the first form of cancer for which a vaccine therapy – a treatment that stimulates the immune system to attack a disease – was approved by the U.S. Food and Drug Administration (FDA).
That vaccine, called Provenge, was cleared by the FDA in 2010 to treat advanced prostate cancer that no longer responds to hormone therapy but is causing few symptoms. The vaccine is made by removing some white blood cells – key components of the immune system – from a patient and sending them to a lab where they’re exposed to a protein that will help them attack prostate cancer cells. They’re then re-infused into the patient. Although the vaccine doesn’t cure or stop prostate cancer from growing, it can help patients live several months longer.
Another therapeutic vaccine for prostate cancer, called PROSTVAC, uses a virus that has been genetically modified to contain prostate-specific antigen (PSA), a protein produced by prostate cells and whose production often increases in men with prostate cancer. If it works as intended, it will spur the immune system to respond to the virus by recognizing and destroying cancer cells containing PSA. Early clinical trials of this vaccine have produced promising results and a larger trial is planned.
A vaccine called GVAX is made of prostate cancer cells that are irradiated and then engineered to produce the protein GM-CSF, which stimulates immune system cells to grow and reproduce. Most clinical trials of GVAX have paired it with other immunotherapy agents or with hormone therapy, and it has shown promising results in men with advanced, hormone-resistant prostate cancer.
Prostate cancer is one of many types of cancer in which researchers are testing agents known as immune checkpoint inhibitors, which are designed to lower cancer cells’ defenses against an immune system attack. Trials are currently under way of the drugs pembrolizumab and nivolumab, which target the checkpoint protein PD-1, and ipilimumab, which inhibits the protein CTLA4, in men with advanced prostate cancer. Dana-Farber investigators are leading several such trials – including one that involves pembrolizumab and one that involves the agent DVCAC – for certain patients with prostate cancer.
Even as these trials are under way, scientists are considering ways of making checkpoint inhibitors more effective. One promising option is pairing such inhibitors with a prostate cancer vaccine.