RC48 Monotherapy or Combination With Envafolimab for CDK12 Alterations mCRPC With Standard Treatment Failure

This study is testing a targeted antibody-drug therapy (RC48, which delivers chemotherapy directly to cancer cells that overexpress HER2) alone or combined with an immunotherapy drug (envafolimab, which helps the immune system attack cancer), in men with prostate cancer that is no longer responding to hormone therapy and has a specific gene change called a CDK12 mutation. **You may be eligible if...** - You are 18 or older - You have prostate cancer that has spread and is no longer responding to hormone-lowering treatments (castration-resistant) - Your tumor has been confirmed to be HER2-positive on a lab test - Your tumor has a CDK12 gene change combined with HER2 amplification or overexpression - You have already tried at least one newer hormone therapy (like abiraterone or enzalutamide) - You have never received HER2-targeted drugs before **You may NOT be eligible if...** - You have not received the required prior treatments - Your organ function (blood, liver, kidneys) does not meet the minimum requirements - You have previously received HER2-targeted therapy (antibodies, pills, or antibody-drug conjugates) - Your general health or performance status is too low to tolerate treatment Talk to your doctor to see if this trial is right for you.