Inclusion Criteria:

          -  Subject has a diagnosis of primary AML or AML secondary to myelodysplastic syndrome
             (MDS) according to World Health Organization (WHO) classification as determined by
             pathology review at the treating institution.

          -  Subject is refractory to or relapsed after first-line AML therapy (with or without
             HSCT)

               -  Refractory to first-line AML therapy is defined as:

                  a. Subject did not achieve CR/CRi/CRp under initial therapy. A subject eligible
                  for standard therapy must receive at least 1 cycle of an anthracycline containing
                  induction block in standard dose for the selected induction regimen. A subject
                  not eligible for standard therapy must have received at least 1 complete block of
                  induction therapy seen as the optimum choice of therapy to induce remission for
                  this subject.

               -  Untreated first hematologic relapse is defined as:

                    1. Subject must have achieved a CR/CRi/CRp with first-line treatment and has
                       hematologic relapse.

          -  Subject is positive for FLT3 mutation in bone marrow or whole blood as determined by
             the central lab. A subject with rapidly proliferative disease and unable to wait for
             the central lab results can be enrolled based on a local test performed after
             completion of the last interventional treatment. Subjects can be enrolled from a local
             test result if the subjects have any of the following FLT3 mutations: FLT3-internal
             tandem duplication (ITD), FLT3-tyrosine kinase domain (TKD)/D835 or FLT3-TKD/I836.

          -  Subject has an Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2.

          -  Subject is eligible for preselected salvage chemotherapy.

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

               -  Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 x
                  upper limit of normal (ULN)

               -  Serum total bilirubin (TBL) ≤ 1.5 x ULN

               -  Serum creatinine ≤ 1.5 x ULN or an estimated glomerular filtration rate of > 50
                  mL/min as calculated by the Modification of Diet in Renal Disease equation.

          -  Subject is suitable for oral administration of study drug.

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

        Inclusion Criteria for COE:

        Subject is eligible for the COE if they continue to meet all inclusion criteria from the
        main protocol in addition to the following when the subject is evaluated for eligibility to
        participate in the COE portion of the study:

          -  Subject has received study treatment of either LoDAC, MEC or FLAG and has no response
             or progressive disease.

          -  Subject haven't received other antileukemic therapy after EoT (hydroxyurea is allowed
             for the control of peripheral leukemic blasts in subjects with leukocytosis).

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

        Exclusion Criteria:

          -  Subject was diagnosed as acute promyelocytic leukemia.

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

          -  Subject has AML secondary to prior chemotherapy for other neoplasms (except for MDS).

          -  Subject is in second or later hematologic relapse or has received salvage therapy for
             refractory disease.

          -  Subject has clinically active central nervous system leukemia..

          -  Subject has been diagnosed with another malignancy, unless disease-free for at least 5
             years. Subjects with treated nonmelanoma skin cancer, in situ carcinoma or cervical
             intraepithelial neoplasia, regardless of the disease-free duration, are eligible for
             this study if definitive treatment for the condition has been completed. Subjects with
             organ-confined prostate cancer with no evidence of recurrent or progressive disease
             are eligible if hormonal therapy has been initiated or the malignancy has been
             surgically removed or treated with definitive radiotherapy.

          -  Subject has received prior treatment with ASP2215 or other FLT3 inhibitors (with the
             exception of sorafenib and midostaurin used in first-line therapy regimen as part of
             induction, consolidation and/or maintenance).

          -  Subject has clinically significant abnormality of coagulation profile, such as
             disseminated intravascular coagulation.

          -  Subject has had major surgery within 4 weeks prior to the first study dose.

          -  Subject has radiation therapy within 4 weeks prior to the first study dose.

          -  Subject has congestive heart failure New York Heart Association (NYHA) class 3 or 4 or
             subject with a history of congestive heart failure NYHA class 3 or 4 in the past,
             unless a screening echocardiogram (ECHO) performed within 1 month prior to study entry
             results in a left ventricular ejection fraction (LVEF) that is ≥ 45%.

          -  Subject with mean of triplicate Fridericia-corrected QT interval (QTcF) > 450 ms at
             Screening based on central reading.

          -  Subject with Long QT Syndrome at Screening.

          -  Subject with hypokalemia and hypomagnesemia at Screening (defined as values below
             lower limit of normal [LLN]).

          -  Subject requires treatment with concomitant drugs that are strong inducers of CYP3A.

          -  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 1 (5HT1R) or 5-hydroxytryptamine receptor 2B (5HT2BR)
             receptors or sigma nonspecific receptor with the exception of drugs that are
             considered absolutely essential for the care of the subject.

          -  Subject has an active uncontrolled infection.

          -  Subject is known to have human immunodeficiency virus infection.

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

          -  Subject has any condition which makes the subject unsuitable for study participation.

          -  Subject has active clinically significant (graft-versus-host disease) GVHD or is on
             treatment with systemic corticosteroids for GVHD.

          -  Subject has an FLT3 mutation other than the following: FLT3-ITD, FLT3-TKD/D835 or
             FLT3-TKD/I836.

        Exclusion Criteria for COE:

        Subject will be excluded from participation in the COE if they meet any of the exclusion
        criteria listed in the main protocol or when the subject is evaluated for eligibility to
        participate in the COE portion of the study.