A Study of Terbium 161 (161Tb)-RAD402 in Participants With CRPC

This study is testing a new radioactive drug called 161Tb-RAD402 in men with castration-resistant prostate cancer (CRPC) — a form of prostate cancer that has stopped responding to hormone-lowering therapy. **You may be eligible if...** - You are a male aged 18 or older - You have confirmed advanced or metastatic prostate cancer that has progressed despite hormone therapy (castrate testosterone levels) - Your PSA (a prostate cancer marker) is rising, or your cancer has spread or grown on imaging - You have received prior standard treatments including certain hormone-blocking drugs **You may NOT be eligible if...** - You have poor kidney, liver, or bone marrow function - You have had certain prior radioactive treatments - You have significant other medical conditions that would make participation unsafe Talk to your doctor to see if this trial is right for you.