|Inclusion Criteria:||1) Male or female subjects >/=55 years of age at the time of signing the ICD|
2) Newly diagnosed, histologically confirmed de novo AML or AML secondary to prior myelodysplastic disease
3) Should have undergone induction therapy with intensive chemotherapy with or without consolidation therapy
4) Should have achieved first CR/CRi status within 3 months prior to randomization, as evidenced by the following: Complete Remission (CR) -- < 5% blasts in bone marrow, absence of blasts with Auer rods, absence of extramedullary disease, independence on blood transfusions, peripheral neutrophil count > 1.0 x 10^9/L, platelet count >/=100 x 109/L; or Complete Remission with Incomplete Blood Count Recovery (CRi) -- < 5% blasts in bone marrow, absence of blasts with Auer rods, absence of extramedullary disease, independence on blood transfusions, peripheral neutrophil count < 1.0 x 10^9/L or platelet count < 100 x 10^9/L.
5) ECOG performance status of 0, 1, 2 or 3
6) Adequate bone marrow function based on ANCs >/= 0.5 x 10^9/L and platelet counts >/= 20,000 x 10^9/L
7) Adequate organ function, defined as: Serum bilirubin </=1.5 times the upper limit of normal (ULN); Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) </=2.5 times the ULN; Serum creatinine </=2.5 times the ULN
8) Females of child bearing potential (FCBP)* may participate, providing they meet the following conditions: Agree to practice abstinence; or Agree to use at least two effective contraceptive methods (oral, injectable, or implantable hormonal contraceptive; tubal ligation; intra-uterine device; barrier contraceptive with spermicide; or vasectomized partner) throughout the study, and for 3 months following the last dose of oral azacitidine; and Have a negative serum pregnancy test (sensitivity of at least 25 mIU/mL) at screening; and Have a negative serum or urine pregnancy test (Investigator's discretion) within 72 hours prior to starting study therapy in the double-blind treatment phase (note that the screening serum pregnancy test can be used as the test prior to starting study therapy in the double-blind treatment phase if it is performed within the 72-hour timeframe).
9) Male subjects with a female partner of childbearing potential must agree to practice abstinence or to the use of a physician-approved contraceptive method throughout the course of the study and avoid fathering a child during the course of the study and for 3 months following the last dose of azacitidine
10) Understand and voluntarily sign an ICD prior to any study related assessments/procedures are conducted
11) Able to adhere to the study visit schedule and other protocol requirements
12) Ability to swallow study medication