Inclusion Criteria:

• Understand and voluntarily sign an informed consent form.
• Age >/= to 16 years at the time of signing the informed consent form.
• Diagnosis of AML [other than acute promyelocytic leukemia (APL)] with refractory/relapsed disease. Patients with newly diagnosed AML will be eligible if not a candidate for intensive chemotherapy. Patients with high-risk (intermediate-2 or high by IPSS or >/= 10% blasts) MDS will also be eligible. All non-hematological toxicity of previous cancer therapy should have resolved to </= grade 1 (except alopecia or other toxicities not involving major organs).
• ECOG performance status of </=3 at study entry.
• Laboratory test results within these ranges (unless due to leukemia): Serum creatinine </= 2 mg/dL Total bilirubin </= 2 mg/dL AST (SGOT) and/or ALT (SGPT) </= 2.5 x ULN or </= 5 x ULN if related to disease
• Women of childbearing potential (WCBP) must have a negative urine pregnancy test within 7 days and must either commit to continued abstinence from heterosexual intercourse or adopting at least one highly effective method of contraception. These methods include intra-uterine device, tubal ligation, partner's vasectomy, hormonal birth control pills. Men must agree not to father a child and agree to use a condom if his partner is of child bearing potential.

Exclusion Criteria:

• Pregnant or breastfeeding females.
• Any condition, including the presence of laboratory abnormalities, which places the patient at unacceptable risk.
• Use of any other experimental drug or therapy for leukemia within 14 days unless there is clear evidence of rapid disease progression.
• Use of hydrea to control proliferative disease will be allowed prior to starting therapy on study and for up to 7 days each during cycle 1-3 (Maximum daily dose of 7gm).