A Study of ASP2215 Versus Salvage Chemotherapy in Patients With Relapsed or Refractory Acute Myeloid Leukemia (AML) With FMS-like Tyrosine Kinase (FLT3) Mutation

Subjects considered an adult according to local regulations at the time of signing informed
consent may participate in this study. Subjects will be randomized in a 2:1 ratio to receive
ASP2215 or salvage chemotherapy. Subjects will enter the screening period up to 14 days prior
to the start of treatment. Prior to randomization, a salvage chemotherapy regimen will be
pre-selected for each subject; options will include low-dose cytarabine (LoDAC), azacitidine,
mitoxantrone, etoposide, and intermediate-dose cytarabine (MEC), or fludarabine, cytarabine,
and granulocyte colony-stimulating factor (G-CSF) with idarubicin (FLAG-IDA). The
randomization will be stratified by response to first-line therapy and pre-selected salvage
chemotherapy. Subjects will be administered treatment over continuous 28-day cycles.

After treatment discontinuation, subjects will have a pre-hematopoietic stem cell transplant
(HSCT)/end-of-treatment visit within 7 days after treatment discontinuation, followed by a
30-day follow-up for safety, in which a telephone contact with the subject is sufficient
unless any assessment must be repeated for resolution of treatment-related adverse events
(AEs). After that, long term follow-up will be done every 3 months up to 3 years from the
subject's end-of-treatment visit.

Inclusion Criteria:

- Subject has a diagnosis of primary acute myeloid leukemia (AML) or AML secondary to
myelodysplastic syndrome (MDS) according to WHO classification (2008) as determined by
pathology review at the treating institute.

- Subject is refractory to or relapsed after first-line AML therapy (with or without
hematopoietic stem cell transplant (HSCT)).

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

1. Subject did not achieve complete remission/complete remission with incomplete
hematologic recovery/complete remission with incomplete platelet recovery
(CR/CRi/CRp) under initial therapy. A subject eligible for standard therapy must
receive at least one 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 one 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 (criteria as defined by [Cheson et
al, 2003], see Section 5.3) 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 they 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 pre-selected salvage chemotherapy.

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

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

- Serum total bilirubin ≤ 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.

- Female subject must either:

- Be of non-child bearing potential:

1. post-menopausal (defined as at least 1 year without any menses) prior to
Screening, or

2. documented as surgically sterile (at least 1 month prior to Screening)

- Or, if of childbearing potential,

1. Agree not to try to become pregnant during the study and for 180 days after
the final study administration

2. And have a negative urine pregnancy test at Screening

3. And, if heterosexually active, agree to consistently use highly effective
contraception per locally accepted standards in addition to a barrier method
starting at Screening and throughout the study period and for 180 days after
the final study drug administration.

- Female subject must agree not to breastfeed 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 and their female partners who are of childbearing potential must be using
highly effective contraception per locally accepted standards in addition to a barrier
method 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 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 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 (DIC).

- 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 performed within 3 months prior to study entry
results in a left ventricular ejection fraction that is ≥ 45%.

- Subject requires treatment with concomitant drugs that are strong inducers of
cytochrome P450 (CYP)3A.

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

- Subjects with Long QT Syndrome at Screening.

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

- Subject requires treatment with concomitant drugs that are strong inhibitors or
inducers of P glycoprotein (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) 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 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.