Inclusion Criteria:

          -  Confirmed advanced hematologic malignancies;

        Phase 1:

          -  High-risk MDS/CMML (defined as ≥ 10% peripheral blood or marrow blasts and/or IPSS
             score ≥ 1.5) and relapsed or refractory to prior therapy

          -  AML relapsed or refractory to prior therapy, or ≥ 60 years of age and not a candidate
             for other therapies

        Phase 2a:

          -  MDS/CMML, relapsed from, or refractory to, prior HMA therapy; the latter defined as
             failure to achieve clinical remission (CR), partial remission (PR) or hematologic
             improvement (HI) after previous HMA therapy (≥ 4 cycles of azacitidine or decitabine),
             or progression during, or toxicity to previous HMA therapy precluding further HMA
             treatment, and,

          -  Bone marrow blast count ≥ 10% or peripheral blast count ≥ 5%, or IPSS-R score ≥ 3.5.

               -  At least 3 weeks beyond the last chemotherapy, targeted anticancer agent, major
                  surgery or experimental treatment and recovered from all acute toxicities (≤
                  Grade 1). Hydroxyurea used to control peripheral blast counts is permitted up to
                  Day 7 of treatment on study.

               -  Adequate performance status: ECOG ≤ 2;

               -  Adequate renal and hepatic function:

          -  creatinine ≤ 2.0 mg/dL, or calculated creatinine clearance ≥ 45 mL/min

          -  total bilirubin ≤ 2 times the upper limit of normal (ULN)

          -  ALT/AST ≤ 2 times ULN

               -  Negative serum pregnancy test

               -  Ability to provide written informed consent

        Exclusion Criteria:

          -  Known history of coronary artery disease, angina, myocardial infarction, congestive
             heart failure, cardiac arrhythmia or any other type of heart disease present within
             the last 6 months

          -  Known family history of hereditary heart disease

          -  QT interval corrected for rate (QTc) > 450 msec on the electrocardiogram (ECG)
             obtained at Screening

          -  Concomitant medication(s) that may cause QTc prolongation or induce Torsades de
             Pointes, with the exception of anti-microbials that are used as standard of care to
             prevent or treat infections and other such drugs that are considered by the
             Investigator to be essential for the care of the patient.

          -  Presence of active central nervous system (CNS) leukemia. Subjects adequately treated
             for CNS leukemia documented by 2 consecutive cerebrospinal fluid samples negative for
             leukemia cells are eligible. Subjects with no history of CNS leukemia will not be
             required to undergo cerebrospinal fluid sampling for eligibility.

          -  Known positive for HIV, hepatitis B virus surface antigen (HBsAg), or hepatitis C
             virus (HCV).

          -  Active infection requiring IV anti-infective usage within the last 7 days prior to
             study treatment.

          -  Any other medical intervention or condition which could compromise adherence to study
             requirements or confound the interpretation of study results.

          -  Pregnant or breast-feeding.

          -  Treatment with any investigational product within 28 days prior to Screening.