Inclusion Criteria:

          1. Patients must have pathologically-confirmed acute leukemia, refractory or relapsed
             after standard therapy for the disease or for which conventional systemic chemotherapy
             is not reliably effective or no effective therapy is available Phase II Only: Patient
             must have histologically or pathologically confirmed diagnosis of AML based on WHO
             classification that is refractory after standard therapy, or for which conventional
             systemic chemotherapy is not reliably effective, or no effective therapy is available.
             Patients aged 60 years or older with newly diagnosed AML who are not eligible for, or
             who refuse, standard care are also eligible.

          2. Aged ≥ 18 years.

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

          4. Adequate clinical laboratory values (i.e., plasma creatinine <= 1.5 x upper limit of
             normal (ULN) for the institution, bilirubin <=1.5 x ULN, alanine transaminase (ALT)
             and aspartate transaminase (AST) <= 2.5 x ULN).

          5. Absence of CNS involvement by leukemia.

          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.
             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 may be administered up to day 5
             of the first cycle.

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

          3. Extensive prior radiotherapy to more than 30% of bone marrow reserves, or prior bone
             marrow/stem cell transplantation.

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

          5. A pregnant or lactating woman.

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

          7. Patient has acute promyelocytic leukemia (APL).

          8. Patients with known HIV, HBV or HCV infection (note: testing for these infections is
             not required).

          9. Documented or known clinically significant bleeding disorder.