This is a multicenter, open-label, Phase Ia/b dose escalation study of safety, pharmacodynamics, and pharmacokinetics of APTO-253 in ascending cohorts (3+3 design) to determine the MTD or recommended dose in patients with relapsed or refractory acute myelogenous leukemia (AML) or high-risk MDS patients. This is to be followed by a cohort expansion phase at the MTD or recommended dose.
