Enzalutamide With or Without Vaccine Therapy for Advanced Prostate Cancer

Background: \- Enzalutamide is a hormone therapy that is used to treat advanced prostate cancer. It is given after chemotherapy and surgery to help the body destroy the cancer cells. A new possible way of treating prostate cancer is using a vaccine that may help stimulate the immune system. It will help white blood cells recognize and kill the cancer cells in and around the prostate. Researchers want to see whether this vaccine, given with enzalutamide, is more effective at treating advanced prostate cancer than enzalutamide alone. Objectives: \- To compare the safety and effectiveness of enzalutamide with and without vaccine therapy for advanced prostate cancer. Eligibility: \- Men at least 18 years of age who have advanced castration-resistant prostate cancer. Design: * Participants will be screened with a physical exam and medical history. Blood and urine samples will be collected. Imaging studies will be used to monitor the cancer before treatment. * Participants will be separated into two groups. One group will have enzalutamide and the study vaccine. The other group will have enzalutamide alone. * All participants will take enzalutamide once a day. They will take the drug during 4-week cycles of treatment. * Treatment will be monitored with frequent blood tests and imaging studies. Participants will continue to take the study drug for as long as the cancer does not grow, and the side effects are not severe. * The vaccine group of participants will also have the new study vaccine. They will have a single injection on the first day of the first study cycle. There will be regular booster injections afterward. There will be one on day 15 of the first cycle, the first day of the second cycle. The vaccine will then be given every 4 weeks for the next four cycles, and then every 12 weeks (every 3 cycles) thereafter. Participants will continue to have the study vaccine for as long as the cancer does not grow, and the side effects are not severe.