REGN21353 Alone or in Combination With Nezastomig for Metastatic Castration-Resistant Prostate Cancer in Adult Participants

This study will test an experimental Regeneron drug called REGN21353 ("study drug") to see if it can help treat previously treated prostate cancer that has spread (also called metastatic castration-resistant prostate cancer or mCRPC). Some participants may get additional experimental drugs in combination with REGN21353. These additional drugs are nezastomig and sarilumab. "Experimental" means that the drugs are being tested and have not been approved for use in prostate cancer by a country's national health agency that gives approval for new medicines to be prescribed. The study is looking at: * What is the best dose of REGN21353 alone and together with nezastomig for treating prostate cancer * What side effects REGN21353 alone and together with nezastomig might cause * How well REGN21353 alone and together with nezastomig works * How much REGN21353 alone and together with nezastomig is in the blood at different times * If the body reacts to REGN21353 alone or together with nezastomig, in a way that may cause them to not work as well * How REGN21353 alone and together with nezastomig could affect prostate cancer, which can help researchers understand why REGN21353 alone or together with nezastomig work better in some than others