A Study to Learn How Safe AZD6621 is, How Well it Works, and How it Moves Throughout the Body Over Time, in Adult Male Participants With Metastatic Prostate Cancer

This trial is testing a new drug called AZD6621 to evaluate its safety, effectiveness, and how the body processes it in men with metastatic prostate cancer that has stopped responding to hormone therapy (called castration-resistant prostate cancer). **You may be eligible if...** - You are a male aged 18 or older - You have been diagnosed with metastatic prostate cancer that has spread and is no longer controlled by hormone therapy - Your testosterone levels are very low (at or below 50 ng/dL) from surgical or medical castration - Your prostate cancer has progressed despite castrate levels of testosterone - Your general health and organ function meet study requirements **You may NOT be eligible if...** - You have not had prior hormone therapy for prostate cancer - Your organ function (liver, kidneys, blood counts) does not meet required thresholds - You have other conditions that prevent safe study participation Talk to your doctor to see if this trial is right for you.