This study looks at a new treatment for men with a type of prostate cancer known as *progressive metastatic castrate resistant prostate cancer (mCRPC)*. This means the cancer has spread and doesn’t respond to treatments that lower testosterone, a male hormone. The study has two parts. The first part (Phase I) checks if the combination of two drugs, **tulmimetostat (DZR123)** and **JSB462 (luxdegalutamide)**, is safe and how much people can take. The second part (Phase II) compares this combo to regular treatment to see which works better. Participants must be adult men with mCRPC, have had certain previous treatments, and meet specific medical criteria. The study will not include anyone who has had certain previous treatments or has allergies to study drugs. **Key Points:** - The study includes two parts: Phase I to find safe doses and Phase II to compare treatments. - Participants must have specific medical history and conditions related to mCRPC. - Certain previous treatments or health conditions might disqualify participation. For more details on specific criteria, contact the study team.