This research study is about treating advanced prostate cancer with two medicines called pembrolizumab and lenvatinib. Prostate cancer is a disease where cells in the prostate gland grow uncontrollably. If this cancer spreads to other parts of the body, it is called metastatic prostate cancer. In this study, treatment cycles are 21 days long, and you can have up to 35 cycles. You will continue treatment until the cancer progresses, side effects are too severe, or you decide to stop.

To join, you must be at least 18 years old, have a certain type of prostate cancer, and be in good health overall. You cannot join if you've had certain treatments or have specific health issues. You also need to agree to use birth control and not donate sperm during the study and for 120 days after.

• The study could last up to 35 cycles (around 2 years).
• You must visit the doctor regularly for checkups.
• Check with your doctor about any possible side effects.