Venetoclax in Combination With ASTX727 for the Treatment of Chronic Myelomonocytic Leukemia and Other Myelodysplastic Syndrome/Myeloproliferative Neoplasm

PRIMARY OBJECTIVE: I. To evaluate the complete remission rates of ASTX727 and ASTX727 plus venetoclax in subjects with CMML and non-CMML MDS/MPN with excess (\>= 5%) blasts. SECONDARY OBJECTIVES: I. To evaluate the overall response rate (complete response \[CR\] + partial response \[PR\] + marrow response with erythroid response) of ASTX727 versus ASTX727 + venetoclax in this patient population. II. To determine the overall survival, progression-free survival, allogeneic hematopoietic stem cell transplantation rate, clearance of the malignant clone, clonality at time of hematologic remission, number of red cell and platelet transfusions required and toxicity of ASTX727 versus ASTX727 + venetoclax. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I (COMBINATION THERAPY): Patients receive ASTX727 orally (PO) once daily (QD) on days 1-5 of each cycle and venetoclax PO QD on days 1-14 of each cycle. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients also undergo bone marrow biopsy and aspiration and collection of blood samples throughout the study and undergo buccal swab sample collection at screening. ARM II (MONO THERAPY): Patients receive ASTX727 PO QD on days 1-5 of each cycle. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients who do not have response to treatment may cross over to Arm I. Patients also undergo bone marrow biopsy and aspiration and collection of blood samples throughout the study and undergo buccal swab sample collection at screening. After completion of study treatment, patients are followed up every 6 months for 5 years or until death, whichever occurs first.