A Clinical Study to Evaluate the Safety, Tolerability and Preliminary Efficacy of [225Ac]Ac-PSMA-XT Injection in Patients With Metastatic Castration-resistant Prostate Cancer

Inclusion Criteria: 1. have the ability to understand and sign an approved informed consent form (ICF). 2. \>= 18 years old. 3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 4. have a life expectancy \>6 months. 5. have histological, pathological, and/or cytological confirmation of prostate cancer. 6. PSMA Positron Emission Tomography (PET)/Computed Tomography (CT) scan positive 7. have a castrate level of serum/plasma testosterone (\<50 ng/dL or \<1.7 nmol/L). 8. have received at least one NAAD (such as enzalutamide and/or abiraterone)； patients must have been previously treated undergone at least 1-2 prior taxane-based chemotherapy regimens or be unsuitable for taxane therapy (unsuitability includes contraindications, investigator-determined ineligibility, or patient refusal) in mCRPC stage. 9. progressive mCRPC. 10. 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. Known other malignancies. 2. Any systemic anti-cancer therapy (e.g. chemotherapy, immunotherapy or biological therapy within 28 days prior to day of enrollment. 3. Known hypersensitivity to the components of the study therapy or its analogs. 4. A superscan as seen in the baseline bone scan. 5. Patients with a history of Central Nervous System (CNS) metastases. 6. Uncontrolled, intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, cardiac arrhythmia, or other severe complications.