Inclusion Criteria:

          -  Patients with a diagnosis of relapsed or refractory acute myeloid leukemia (AML) (or
             biphenotypic or bilineage leukemia including a myeloid component) or myelodysplastic
             syndrome

          -  For myelodysplastic syndrome (MDS) patients, patients must have no response,
             progression, or relapse following at least 4 cycles of azacytidine or decitabine;
             and/or intolerance defined as grade >= 3 drug-related toxicity precluding continued
             therapy

          -  Age >= 18 years

          -  Subjects must have documented RUNX1 gene mutation

          -  Eastern Cooperative Oncology Group (ECOG) performance status =< 2

          -  Creatinine < 2 unless related to the disease

          -  Direct bilirubin < 2x upper limit of normal (ULN) unless increase is due to Gilbert's
             disease or leukemic involvement

          -  Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) < 3x ULN unless
             considered due to leukemic involvement

          -  In the absence of rapidly proliferative disease, the interval from prior treatment to
             time of initiation will be at least 7 days for cytotoxic or non-cytotoxic (i.e.
             immunotherapy) agents. Oral hydroxyurea and/or cytarabine (up to 2 g/m^2) for patients
             with rapidly proliferative disease is allowed before the start of study therapy, as
             needed, for clinical benefit and after discussion with the principal investigator (PI)

          -  Male subjects must agree to refrain from unprotected sex and sperm donation from
             initial study drug administration until 90 days after the last dose of study drug

          -  Willing and able to provide informed consent

        Exclusion Criteria:

          -  Patients with t(15;17) karyotypic abnormality or acute promyelocytic leukemia
             (French-American-British [FAB] class M3-AML)

          -  Patients with any concurrent uncontrolled clinically significant medical condition
             including active infection or psychiatric illness, which could place the patient at
             unacceptable risk of study treatment

          -  Patients with active graft-versus-host-disease (GVHD) status post stem cell transplant
             (patients without active GVHD on chronic suppressive immunosuppression and/or
             phototherapy for chronic skin GVHD are permitted after discussion with the PI)

          -  Patients with any severe gastrointestinal or metabolic condition which could interfere
             with the absorption of oral study medications

          -  Known active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection or known
             human immunodeficiency virus (HIV) infection

          -  Subject has a white blood cell count > 25 x 10^9/L. (Note: Hydroxyurea is permitted to
             meet this criterion.)

          -  Nursing women, women of childbearing potential (WOCBP) with positive urine pregnancy
             test, or women of childbearing potential who are not willing to maintain adequate
             contraception

               -  Appropriate highly effective method(s) of contraception include oral or
                  injectable hormonal birth control, intrauterine device (IUD), and double barrier
                  methods (for example a condom in combination with a spermicide)