This was a multicenter, open-label, phase I/II study to evaluate the safety and tolerability, radiation dosimetry and pharmacokinetic characteristics, and efficacy of [177Lu] Lu-XT033 injection in patients with metastatic prostate cancer, including a phase I study and a phase II extension study.

The study for each participant consisted of a Screening period, a Treatment period and a Follow-up period.

In phase I,Six subjects were enrolled in the 1.11 Gbq (30 mCi) group of [177Lu] Lu-XT033 Injection. The last subject in this group completed the 4-week observation period after the first dose, With the consent of the Safety Monitoring Committee (SRC), 6 subjects were enrolled in the 1.85 Gbq (50 mCi) group. Both groups used 8 ± 1 weeks as the dosing interval for a total of 4 doses.In phase II,Subjects who met the inclusion and exclusion criteria were treated with [177Lu] Lu-XT033 injection at the recommended phase II dose（RP2D）.After Cycle 4 treatment and prior to Cycle 5 treatment, the investigator assessed the following criteria to determine whether:

The patient showed evidence of response (i.e. radiological, PSA, clinical benefit)

The patient had signs of residual disease on CT with contrast/MRI or bone scan

The patient had shown good tolerance to the [177Lu] Lu-XT033 Injection

If the patient met all of the criteria above and agreed to continue with additional treatment of [177Lu] Lu-XT033, the Investigator could administer 2 additional cycles. A maximum of 6 cycles of [177Lu] Lu-XT033 as allowed.

All subjects continued to undergo safety, tolerability, and efficacy assessments until the study-specified visit occurred or the subject was lost to follow-up or death whichever came first.

Inclusion Criteria:

1. Patients must have the ability to understand and sign an approved informed consent form (ICF).
2. Patients must be >= 18 and <＝80 years of age.
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
4. Patients must have a life expectancy >6 months.
5. Patients must have histological, pathological, and/or cytological confirmation of prostate cancer.
6. Patients must be 68Ga-PSMA-11 Positron Emission Tomography (PET)/Computed Tomography (CT) scan positive。
7. Patients must have a castrate level of serum/plasma testosterone (<50 ng/dL or <1.7 nmol/L).
8. Patients must have received at least one NAAD (such as enzalutamide and/or abiraterone)； Patients must have been previously treated with at least 1, but no more than 2 previous taxane regimens.
9. Patients must have progressive mCRPC.
10. Patients must have adequate organ function。
11. Subjects of childbearing potential voluntarily use an effective method of contraception, such as condoms, oral or injectable contraceptives, Intra-uterine device（IUD）,etc., during treatment and within 6 months of the last use of the trial drug.

Exclusion Criteria:

1. Previous treatment with any of the following within 6 months of enrollment: Strontium-89, Samarium-153, Rhenium-186, Rhenium-188, Radium-223, hemi-body irradiation. Previous PSMA-targeted radioligand therapy is not allowed.
2. Known other malignancies.
3. Any systemic anti-cancer therapy (e.g. chemotherapy, immunotherapy or biological therapy within 28 days prior to day of enrollment.
4. Known hypersensitivity to the components of the study therapy or its analogs.
5. A superscan as seen in the baseline bone scan.
6. Patients with a history of Central Nervous System (CNS) metastases.
7. Uncontrolled, intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, cardiac arrhythmia, or other severe complications.