This will be a Phase 1, open-label study of DS-3032b to assess its safety and tolerability and identify a Maximum Tolerated Dose (MTD)/tentative Recommended Phase II Dose (RP2D) in subjects with refractory or relapsed Acute Myelogenous Leukemia (AML), Acute Lymphocytic Leukemia (ALL), Chronic Myelogenous Leukemia (CML) in blast phase, or high risk MDS in Part 1-Dose Escalation and refractory or relapsed AML or high risk Myelodysplastic Syndrome (MDS) in Part 2-Dose Expansion.