Targeted Alpha Therapy With 225Actinium-PSMA-I&T of Castration-resISTant Prostate Cancer (TATCIST).

Inclusion Criteria:

Patients must have the ability to understand and sign an approved informed consent (ICF).
Patients must have the ability to understand and comply with all protocol requirements.
Adenocarcinoma of Prostate proven by histopathology.
Life expectancy of 6 months or more.
Unresectable metastases.
Progressive disease, with docetaxel/cabazitaxel or declined taxane therapy by the patient.
If known BRCA mutations or microsatellite instability is present, patients should have received FDA approved therapies such as PARP inhibitors and pembrolizumab, and progressed
Castration resistant disease with confirmed testosterone level ≤50 ng/dL under prior androgen deprivation therapy (ADT)
Positive 68Ga-PSMA-11 PET/CT (or equivalent PSMA-ligand PET/CT) for the majority of measurable disease defined as SUV ≥2.0, including bone-only metastatic disease.
ECOG 0-1.
Hemoglobin concentration ≥ 9.0 g/dL.
Platelet counts ≥100 × 109/L.
White blood cell count ≥ 2.0 × 109/L), ANC>1.5 x109/L
Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) =<3.0 x ULN
Billirubin ≤ 3x ULN.
Albumin ≥ 2.5 g/dL.
Serum/plasma creatinine ≤1.5 × ULN or creatinine clearance ≥50 mL/min based on Cockcroft-Gault formula
Received at least one ARAT in the past.
Patients on anti-androgen therapy are allowed to continue their treatment at the descretion of their oncologists.

Exclusion Criteria:

Less than 6 weeks since last myelosuppressive therapy (including Docetaxel, Cabazitaxel, 223Ra, 153Sm, 177Lu-PSMA-617/other Lu-PSMA RLT ) or other radionuclide therapy permitted (including 223Ra, 153Sm). Patients who received previous treatment with Actinium-225 are excluded.
Urinary tract obstruction as evidenced by Tc-99m DTPA renal scan with diuretics.
Abnormal renal function (eGFR <60 mL/min), baseline Hgb <9g/dL, ANC<1.5 x109/L, platelets <100 x109/L, and PT, INR or PTT ≥1.5xULN
Persistent baseline dry eye or dry mouth from prior RLT.
Persistent prior AEs >Grade 1 from prior anti-cancer therapies.
Administration of an investigational agent ≤60 days or 5 half-lives, whichever is shorter, prior to C1W0.
Known presence of central nervous system metastases or liver metastases.
Active malignancy other than low-grade non-muscle-invasive bladder cancer and non-melanoma skin cancer.
Concurrent illness that may jeopardize the patient's ability to undergo study procedures.
Symptomatic cord compression, or clinical or radiologic findings indicative of impending cordcompression.
Concurrent serious (as determined by the investigator) medical conditions, including, but not limited to, New York Heart Association class III or IV congestive heart failure (see 12.1Appendix 1), unstable ischemia, uncontrolled symptomatic arrhythmia, history of congenital prolonged QT syndrome, uncontrolled infection, known active hepatitis B or C, or other significant co-morbid conditions that in the opinion of the investigator would impair study participation or cooperation.
Major surgery ≤30 days prior to randomization.
Planning to conceive pregnancy during the treatment and up to 6 months after the last treatment.