Inclusion Criteria:

          -  Subject is considered an adult according to local regulation at the time of obtaining
             informed consent.

          -  Subject has a diagnosis of previously-untreated AML according to World Health
             Organization (WHO) classification [Swerdlow et al, 2008] as determined by pathology
             review at the treating institution.

          -  Subject is positive for FLT3 mutation (internal tandem duplication [ITD] or tyrosine
             kinase domain [TKD] [D835/I836] mutation) (or for Korea only: ITD alone or ITD with
             concurrent TKD activating mutation) in bone marrow or whole blood as determined by
             central laboratory. Note: Only requirement of FLT3 mutation assessment by central
             laboratory is only applicable to the randomization portion of the study.

          -  Subject is ineligible for intensive induction chemotherapy by meeting at least 1 of
             the following criteria:

               -  Subject is ≥ 65 years of age and ineligible for intensive induction chemotherapy.

               -  Subject is ≥ 18 to 64 years of age and has any of the following comorbidities:
                  [Ex-US Only]: Congestive heart failure (New York Heart Association {NYHA} class ≤
                  3) or ejection fraction (Ef) ≤ 50%; [US Only]: Severe cardiac disorder e.g.
                  congestive heart failure (New York Heart Association [NYHA] class ≤ 3) requiring
                  treatment, ejection fraction ≤ 50%, or chronic stable angina; [Ex-US Only]:
                  Creatinine > 2 mg/dL (177 µmol/L), dialysis or prior renal transplant; [US Only]:
                  Creatinine clearance < 45 mL/min; ECOG performance status ≥ 2;

               -  [Ex-US Only]: Known pulmonary disease with decreased diffusion capacity of lung
                  for carbon monoxide (DLCO) and/or requiring oxygen ≤ 2 liters per minute; [US
                  Only] Severe pulmonary disorder (e.g., diffusion capacity of lung for carbon
                  monoxide [DLCO] ≤ 65% or forced expiratory volume in the first second [FEV1] ≤
                  65%); Prior or current malignancy that does not require concurrent treatment;
                  Subject has received a cumulative anthracycline dose above 400 mg/m2 of
                  doxorubicin (or cumulative maximum dose of another anthracycline). Any other
                  comorbidity incompatible with intensive chemotherapy must be reviewed and
                  approved by the Medical Monitor during screening and before randomization.

          -  Subject must meet the following criteria as indicated on the clinical laboratory
             tests:

               -  Serum AST and ALT ≤ 3.0 x Institutional upper limit of normal (ULN)

               -  Serum total bilirubin ≤ 1.5 x Institutional ULN

               -  Serum potassium ≥ Institutional lower limit of normal (LLN)

               -  Serum magnesium ≥ Institutional LLN Repletion of potassium and magnesium levels
                  during the screening period is allowed.

          -  Subject is suitable for oral administration of study drug.

          -  Female subject is eligible to participate if female subject is not pregnant and at
             least one of the following conditions applies:

               -  Not a woman of childbearing potential (WOCBP); OR

               -  WOCBP agrees to follow the contraceptive guidance starting at screening and
                  continue throughout the study period, and for at least 180 days after the final
                  study drug administration.

          -  Female subject must agree not to breastfeed starting at screening and throughout the
             study period, and for 60 days after the final study drug administration.

          -  Female subject must not donate ova starting at screening and throughout the study
             period, and for 180 days after the final study drug administration.

          -  Male subject with female partners of childbearing potential must agree to use
             contraception as detailed in Contraception Requirements, starting at screening and
             continue throughout the study period, and for 120 days after the final study drug
             administration.

          -  Male subject must not donate sperm starting at screening and throughout the study
             period and for 120 days after the final study drug administration.

          -  Subject agrees not to participate in another interventional study while on treatment.

        Exclusion Criteria:

          -  Subject was diagnosed as acute promyelocytic leukemia (APL).

          -  Subject has BCR-ABL-positive leukemia (chronic myelogenous leukemia in blast crisis).

          -  Subject has received previous therapy for AML, with the exception of the following:

               -  Emergency leukapheresis

               -  Hydroxyurea

               -  Preemptive treatment with retinoic acid prior to exclusion of APL ≤ 7 days

               -  Growth factor or cytokine support

               -  Steroids

          -  Subject has clinically active central nervous system leukemia.

          -  Subject has been diagnosed with another malignancy that requires concurrent treatment
             (with the exception of hormone therapy limited to those therapies that prevent
             recurrence and/or spread of cancer) or hepatic malignancy regardless of need for
             treatment.

          -  Subject requires treatment with concomitant drugs that are strong inducers of
             cytochrome P450 CYP3A/P-glycoprotein (P-gp).

          -  Subject requires treatment with concomitant drugs that are strong inhibitors or
             inducers of P-gp with the exception of drugs that are considered absolutely essential
             for the care of the subject.

          -  Subject requires treatment with concomitant drugs that target serotonin
             5-hydroxytryptamine receptor 2B (5HT2BR) or sigma nonspecific receptor with the
             exception of drugs that are considered absolutely essential for the care of the
             subject.

          -  Subject has congestive heart failure classified as New York Heart Association Class
             IV.

          -  Subject with mean Fridericia-corrected QT interval (QTcF) > 480 ms at screening based
             on central reading.

          -  Subject with a history of Long QT Syndrome at screening.

          -  [Ex-US Only]: Subject has known pulmonary function tests with diffusion capacity of
             lung for carbon monoxide (DLCO) ≤ 50%, forced expiratory volume in the first second
             (FEV1) ≤ 60%, dyspnea at rest or requiring oxygen or any pleural neoplasm (Transient
             use of supplemental oxygen is allowed.)

          -  Subject has active hepatitis B or C or other active hepatic disorder.

               -  Subjects with positive hepatitis B surface antigen (HBsAg) or detectable
                  hepatitis B DNA are not eligible.

               -  Subjects with negative HBsAg, positive hepatitis B core antibody and negative
                  hepatitis B surface antibody will be eligible if hepatitis B DNA is undetectable.

               -  Subjects with antibodies to hepatitis C virus will be eligible if hepatitis C RNA
                  is undetectable

          -  Subject has any condition which makes the subject unsuitable for study participation,
             including any contraindications of azacitidine.

          -  Subject has a known or suspected hypersensitivity to ASP2215, azacitidine or any
             components of the formulations used.

          -  [US Only]: Subject is ≥ 65 to 74 years of age, suitable for and willing to receive
             intensive induction chemotherapy.