ASTX727, Venetoclax, and Gilteritinib for the Treatment of Newly Diagnosed, Relapsed or Refractory FLT3-Mutated Acute Myeloid Leukemia or High-Risk Myelodysplastic Syndrome

PRIMARY OBJECTIVES: I. To establish the maximum tolerated dose (MTD) of the combination of decitabine and cedazuridine (ASTX727), venetoclax and gilteritinib in patients with relapsed/refractory FLT3- mutated acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). (Phase I) II. To determine the complete response (CR)/incomplete hematologic recovery (CRi) rate of the regimen in patients with newly diagnosed or relapsed/refractory FLT3-mutated AML or high-risk MDS. (Phase II) SECONDARY OBJECTIVES: I. To assess other efficacy endpoints (CR rate, minimal residual disease negativity by flow cytometry, relapse-free survival, overall survival). II. To assess proportion of patients proceeding to hematopoietic stem cell transplantation (HSCT). III. To determine the safety of the combination regimen. EXPLORATORY OBJECTIVES: I. To evaluate the impact of baseline genomic alterations on response and survival of the combination regimen. II. To determine the impact of baseline FLT3 allelic ratio on response and survival. III. To evaluate clonal evolution from diagnosis to relapse using single-cell sequencing. IV. To evaluate potential role of minimal residual disease (MRD) detection by sensitive polymerase chain reaction (PCR)/next generation sequencing (NGS) assays for FLT3 mutations. V. To evaluate leukemia stem cell populations over the course of treatment with the combination regimen. VI. To determine the impact of baseline apoptotic protein levels as assessed by mass cytometry (CyTOF) on response and resistance to the regimen. OUTLINE: This is a phase I, dose-escalation study of gilteritinib followed by a phase II study. INDUCTION (CYCLE 1): Patients receive decitabine and cedazuridine orally (PO) once daily (QD) on days 1-5, venetoclax PO QD on days 1-28, and gilteritinib PO QD on days 1-28 in the absence of disease progression or unacceptable toxicity CONSOLIDATION (CYCLES 2-24): Patients receive decitabine and cedazuridine PO QD on days 1-5, gilteritinib PO QD on days 1-28, and venetoclax PO QD on days 1-21. Treatment repeats every 28 days for up to 23 cycles in the absence of disease progression or unacceptable toxicity. MAINTENANCE (CYCLES 24+): Patients receive gilteritinib PO QD on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days, then every 6 months thereafter.