Inclusion Criteria:

          -  Patients must have histologically confirmed prostate adenocarcinoma that is metastatic
             and castration resistant (mCRPC).

          -  At least 3 metastatic foci avid for PSMA-specific PET agent (CTT1057) uptake on
             Screening PSMA PET.

          -  Has received docetaxol, ineligible for docetaxol, or refused docetaxol for the
             treatment of prostate cancer.

          -  Has progression by the PCWG3 criteria during or after treatment with either
             abiraterone or enzalutamide

          -  Male Age ≥ 18 years.

          -  Has Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 (see
             Appendix 2).

        Demonstrate adequate organ function

        Exclusion Criteria:

          -  Has received previous treatment with radium-223 or another radiopharmaceutical within
             3 months prior to first dose of CTT1403.

          -  Has received cabazitaxel for the treatment of mCRPC.

          -  Has received previous treatment with a therapeutic targeting PSMA.

          -  Has an additional active malignancy requiring therapy that may confound the assessment
             of the study endpoints.

          -  Has clinically significant cardiovascular disease

          -  Has a history of untreated brain metastases

          -  Has a condition requiring systemic treatment with either corticosteroids (> 10 mg
             daily prednisone equivalents) or other immunosuppressive medications within 14 days
             before CTT1403 administration.

          -  Has known positive status for chronic hepatitis B or hepatitis C

          -  Known or suspected myelodysplastic syndrome.

          -  Has any medical condition which in the opinion of the Investigator places the patient
             at an unacceptably high risk for toxicities.