Inclusion Criteria:

          1. One of the following:

             Untreated AML in (de novo or treatment related) patients in the following categories:

               -  Medical conditions that compromise the ability to give cytotoxic chemotherapy as
                  the primary modality.

               -  Patients who decline cytotoxic chemotherapy.

             Patients with AML who have relapsed despite one prior regimen

          2. ECOG performance status 0, 1, or 2

          3. Patients must not have untreated active infections at the time of study entry.

          4. Normal organ function as defined below:

               -  Creatinine < 2 mg/dl.

               -  Total serum bilirubin within institutional limits unless due to hemolysis,
                  Gilbert's syndrome, or ineffective erythropoiesis.

               -  AST(SGOT)/ALT(SGPT) ≤2.5 X institutional upper limit of normal.

          5. Life expectancy of at least three months.

          6. Patients must be informed of the investigational nature of the treatment, results that
             might be expected, and potential toxicities. They must be able to understand and give
             informed written consent according to federal and institutional guidelines.

          7. Declined or ineligible for potentially curative options such as allogeneic stem cell
             transplant.

          8. No chemotherapy or study drugs for >3 weeks prior to starting study.

          9. Women of childbearing potential should be advised to avoid becoming pregnant and men
             should be advised to not father a child while receiving treatment. All men and women
             of childbearing potential must use acceptable methods of birth control throughout the
             study as described below:

               -  Females of childbearing potential: Recommendation is for 2 effective
                  contraceptive methods during the study. Adequate forms of contraception are
                  double-barrier methods (condoms with spermicidal jelly or foam and diaphragm with
                  spermicidal jelly or foam), oral, depo provera, or injectable contraceptives,
                  intrauterine devices, and tubal ligation.

               -  Male patients with female partners who are of childbearing potential:
                  Recommendation is for male and partner to use at least 2 effective contraceptive
                  methods, as described above, during the study or to abstain.

        Exclusion Criteria

          1. Any of the Following:

               -  Treatment for acute myeloid leukemia (AML), including hematopoietic growth
                  factors, < 3 weeks prior to study registration. Exception: Hydroxyurea may be
                  administered to patients with WBC > 30,000/µL

               -  Diagnosis of acute promyelocytic leukemia (APL)

               -  Radiotherapy < 4 weeks prior to study registration

               -  Failure to recover (to < grade 1) from all adverse events associated with prior
                  therapy.

               -  Valproic acid < 2 weeks prior to study registration.

               -  Hypersensitivity to azacytidine, deoxyazacytidine, mannitol, entinostat or
                  components of the entinostat tablet

               -  Any advanced malignant hepatic tumor(s)

          2. Prior therapy with demethylating agents for leukemia treatment within the last four
             months.

          3. Clinical evidence of CNS or pulmonary leukostasis, disseminated intravascular
             coagulation, or central nervous system leukemia.

          4. Serious or uncontrolled medical conditions.

          5. Concurrent use of any other investigational agents.

          6. Known HIV-positive patients.

          7. Pregnancy or breast feeding

          8. Male and female patients who are fertile who do not agree to use an effective barrier
             methods of birth control (i.e. abstinence) to avoid pregnancy during the study and for
             a minimum of 30 days after study treatment.