- Enzalutamide is a well tolerated hormone therapy that is used to treat advanced prostate cancer. It is given to help kill cancer cells and limit cancer cell growth. A new possible way of treating prostate cancer is using a therapeutic cancer vaccine (immune stimulating therapy) that may help activate the immune system against the cancer. The immune stimulating vaccine will help white blood cells recognize and kill the cancer cells throughout the body. This vaccine therapy has been tested in hundreds of patients and is very well tolerated. Researchers want to see whether this vaccine, given with enzalutamide, is more effective at treating advanced prostate cancer than enzalutamide alone.