This open-label clinical study investigates 3D1015 Injection (Lu 177-PSMA-3D1015) in adult males with prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer (mCRPC). Participants will receive intravenous infusions of 3D1015, with treatment regimens dynamically individualized to optimize patient safety and outcomes. The primary objectives are to assess the safety, tolerability, and dosimetry of the injection. Secondary objectives include evaluating preliminary anti-tumor efficacy and exploring the optimal dosing regimen.