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.

Inclusion Criteria:

1. Capable of understanding and providing written informed consent. Willing and able to comply with all study requirements, treatments, and scheduled visits.
2. Male, aged 18 years or older.
3. Histologically or cytologically confirmed prostate adenocarcinoma.
4. Castrate levels of serum/plasma testosterone (< 50 ng/dL or < 1.7 nmol/L).
5. Must be 68Ga-PSMA PET/CT scan positive.
6. ECOG performance status of 0 to 2.
7. Confirmed progressive metastatic castration-resistant prostate cancer (mCRPC) that is refractory to or has progressed following prior treatments.
8. Presence of at least one metastatic lesion at baseline.
9. Adequate Organ Function.
10. Resolution of all prior treatment-related toxicities to Grade ≤ 2 (excluding alopecia).

Exclusion Criteria:

1. Receipt of other systemic anti-cancer therapies within 4 weeks prior to study entry.
2. Life expectancy of < 6 months, as assessed by the investigator.
3. A superscan as seen in the baseline bone scan.
4. Presence of clinically significant, uncontrolled, or unstable concurrent medical conditions that may compromise patient safety or study assessments.
5. Known hypersensitivity or severe intolerance to the study drug, its excipients, or structurally related compounds.
6. Any medical, psychiatric, or logistical condition that, per investigator judgment, would preclude protocol compliance or compromise patient safety.