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 study is being conducted to learn more about the safety, tolerability, and effectiveness of an experimental treatment for metastatic prostate cancer called AZD6621. The study is split into different modules which will look at AZD6621 delivered by different methods. The study is also further split into 2 parts, Part A which will test different dose levels of AZD6621 to determine which doses are the best in terms of safety and side effects (dose escalation), and Part B will further test at least two AZD6621 doses in a larger group of participants (dose expansion).