The purpose of this study is to find out whether treatment with pasritamig and docetaxel prolongs radiographic progression free survival (rPFS) (the length of time from start of treatment until disease worsens as determined by scans) when compared to treatment with docetaxel in participants with metastatic castrate-resistant prostate cancer (mCRPC; a cancer of prostate, a male reproductive gland found below the bladder, that grows despite low levels of male hormones).