Inclusion Criteria:

          1. Histologically or pathologically confirmed diagnosis of AML based on WHO
             classification that has relapsed after, or is refractory to, two, three, or four prior
             induction regimens that may have included intensive chemotherapy (e.g., "7+3"
             cytarabine and daunorubicin), epigenetic therapy (i.e., azacitidine or decitabine), or
             targeted therapy (e.g., FLT-3, IDH-1/2, BCL-2, monoclonal antibody).

             (Relapse is defined as reemergence of ≥5% leukemia blasts in bone marrow or ≥1% blasts
             in peripheral blood ≥90 days after first CR or CR without complete platelet recovery
             (CRp). Refractory AML is defined as persistent disease ≥28 days after initiation of
             intensive induction therapy (up to two induction cycles) or relapse <90 days after
             first CR or CRp. Refractory disease for patients undergoing hypomethylating agent
             induction is defined as lack of remission following at least 2 cycles of epigenetic
             therapy without reduction in bone marrow blast status.)

             Patients with a history of IPSS-R high or very high risk MDS that transformed to AML
             during treatment with hypomethylating drugs and then relapse following or are
             refractory to a subsequent AML induction regimen may be enrolled as Second Salvage AML
             patients. Additionally, patients with a history of MPN in accelerated phase (MPN-AP)
             or high-risk primary myelofibrosis (PMF) that transformed to AML during treatment with
             hypomethylating drugs and then relapse following or are refractory to a subsequent AML
             induction regimen may be enrolled as Second Salvage AML patients.

          2. Aged ≥ 18 years.

          3. ECOG Performance Status of 0, 1 or 2.

          4. Adequate clinical laboratory values (i.e., plasma creatinine <2.5 x upper limit of
             normal (ULN) for the institution, bilirubin <2.5 x ULN, alanine transaminase (ALT) and
             aspartate transaminase (AST) ≤2.5 x ULN).

          5. Absence of active central nervous system (CNS) involvement by leukemia. Patients with
             previously diagnosed CNS leukemia are eligible if the CNS leukemia is under control
             and intrathecal treatment may continue throughout the study.

          6. Absence of uncontrolled intercurrent illnesses, including uncontrolled infections,
             cardiac conditions, or other organ dysfunctions.

          7. Signed informed consent prior to the start of any study specific procedures.

          8. Women of child-bearing potential must have a negative serum or urine pregnancy test.

          9. Male and female patients must agree to use acceptable contraceptive methods for the
             duration of the study and for at least one month after the last drug administration.

        Exclusion Criteria:

          1. The interval from prior treatment to time of study drug administration is < 2 weeks
             for cytotoxic agents or < 5 half-lives for noncytotoxic agents. Exceptions: Use of
             hydroxyurea is allowed before the start of study and is to be discontinued prior to
             the initiation of study treatment. At the investigator's discretion, for patients with
             significant leukocytosis that develops during the early treatment cycles, hydroxyurea
             may be administered. The hydroxyurea should be discontinued as soon as clinically
             appropriate.

          2. Any >grade 1 persistent clinically significant toxicities from prior chemotherapy.

          3. Inadequate Cardiac (left ventricular ejection fraction ≤40%) function.

          4. White blood cell (WBC) count >15,000/μL (Note: Patients considered for possible
             venetoclax-containing regimen must have WBC ≤10k/μL prior to initiating venetoclax
             treatment).

          5. For patients with prior hematopoietic stem cell transplant (HSCT):

               1. Less than 3 months since HSCT

               2. Acute Graft versus Host Disease (GvHD) >Grade 1

               3. Chronic GvHD >Grade 1

          6. Any concomitant condition that in the opinion of the investigator could compromise the
             objectives of this study and the patient's compliance.

          7. A pregnant or lactating woman.

          8. Current malignancies of another type. Exceptions: Patients may participate if they
             have previously treated and currently controlled prostate cancer, or adequately
             treated in situ cervical cancer or basal cell skin cancer, or other malignancies with
             no evidence of disease for 2 years or more.

          9. Patient has acute promyelocytic leukemia (APL).

         10. Patients with known HIV, active HBV or active HCV infection (note: testing for these
             infections is not required). For patients with evidence of chronic hepatitis B virus
             (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if
             indicated. Patients with a history of hepatitis C virus (HCV) infection must have been
             treated and cured. For patients with HCV infection who are currently on treatment,
             they are eligible if they have an undetectable HCV viral load.

         11. Documented or known clinically significant bleeding disorder.