PET Positive

Background: Prostate cancer may return after treatment in 30,000 to 50,000 people each year. There is no clear best way to treat these people. Better treatments are needed. Objective: To test a study drug (enzalutamide), both alone and combined with a second drug (PDS01ADC), in people with prostate cancer that returned after treatment. Eligibility: People aged 18 years and older with prostate cancer that returned after treatment. Design: Participants will be screened. They will have a physical exam, with blood tests. All their urine will be collected for 24 hours. They will have imaging scans of their chest, abdomen, pelvis, and bones. Their ability to perform everyday activities will be assessed. They may opt to give a stool sample. Participants will be treated in 4-week cycles. Enzalutamide is a pill taken by mouth once a day, every day. All participants will be given a supply of this drug to take at home. PDS01ADC is injected under the skin once a month, on the first day of each cycle. Half of the participants will receive both drugs. All participants will visit the clinic once a month. Each visit should last no more than 8 hours. Blood and urine tests will be repeated. All participants will receive the study treatment for 3 cycles. Some participants may need 3 more cycles of treatment with enzalutamide only. This re-treatment can be done only once. Participants will have a follow-up visit 1 month after they finish treatment. After that, they will have visits every 6 weeks for up to 5 years. Imaging scans and blood tests will be repeated. ...