Testing an Anti-cancer Radio-Active Immunotherapy Called Lintuzumab Ac225 in Patients With High-Risk Myelodysplastic Syndrome That Has Not Responded to Other Treatment

Inclusion Criteria: * Patients must have histologically or cytologically confirmed diagnosis of MDS by bone marrow biopsy by World Health Organization (2016) guidelines * Patients with MDS who have progressed or had no response after 6 cycles of azacitidine or 4 cycles of decitabine * For the expansion phase, we will be enrolling 12 more patients at the maximum tolerated dose: 6 patients with prior azacitidine or decitabine treatment and 6 patients with prior treatment with azacitidine or decitabine in combination with venetoclax * Patients with MDS must have ≥ 5% myeloblasts * Patients with demonstration of CD33 positive myeloblasts on flow cytometry using Phycoerythrin (PE) labeled anti-CD33 antibody, done as standard of care testing by every participating site * Age ≥ 18 years. Because no dosing or adverse event data are currently available on the use of lintuzumab-Ac225 in patients \< 18 years of age, children are excluded from this study * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Karnofsky ≥ 60%) * Serum direct bilirubin ≤ 1.5 × institutional upper limit of normal (ULN) * Aspartate aminotransferase (AST)(serum glutamic oxaloacetic transaminase \[SGOT\])/ alanine aminotransferase (ALT) (serum glutamic pyruvic transaminase \[SGPT\]) ≤ 3 × institutional ULN * Creatinine clearance ≥ 50mL/min (Cockcroft-Gault equation) * HIV-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this tr…