• Eligible subjects must meet all of the following criteria:

‣ Subject must have confirmation of diagnosis of AML (except for acute promyelocytic leukemia \[APL\]) or MDS per 2016 World Health Organization (WHO) criteria.

⁃ For AML (except for APL) cohort:

• Previously treated relapsed/refractory AML subjects

∙ Treatment-naïve AML subjects should be:

⁃ 60 years of age OR ≥18 years and \<60 years will be eligible if the subject has at least one of the following co-morbidities, which make the subject unfit for intensive chemotherapy

⁃ For MDS cohort:

‣ Adult TN MDS and R/R MDS: revised International Prognostic Scoring System (IPSS-R) score \> 3 and bone marrow blasts ≥ 5%.

⁃ Subject must have a projected life expectancy of at least 12 weeks.

⁃ Subject must have adequate renal function as demonstrated by a creatinine clearance ≥ 30 mL/min; determined via urine collection for 24-hour creatinine clearance or by the Cockcroft-Gault formula.

⁃ Subject must have adequate liver function