This is a randomized, multi-center, double-blind, placebo-controlled study designed to evaluate the efficacy of crenolanib administered following salvage chemotherapy, consolidation chemotherapy, post bone marrow transplantation and as maintenance in relapsed/refractory AML subjects with FLT3 activating mutation.

Inclusion Criteria:

1. Confirmed diagnosis of AML according to World Health Organization (WHO) 2016 classification
2. Presence of FLT3-ITD and/or D835 mutation(s)
3. Subjects must be primary refractory or relapsed to 1st line intensive treatment for AML or refractory or relapsed after second line of treatment for AML
4. Age ≥ 18 years and ≤ 75 years
5. Adequate hepatic function
6. Adequate renal functions
7. ECOG performance status ≤ 3

Exclusion Criteria:

1. Known clinically active central nervous system(CNS) leukemia
2. Severe liver disease
3. Known, active infection with hepatitis B virus (HBV) or hepatitis C virus (HCV)
4. Prior anti-leukemia therapy within the 14 days prior to randomization. Prior use of quizartinib or gilteritinib must be discontinued 21 days prior to randomization. Prior use of hydroxyurea or other palliative treatment for leukocytosis is allowed.
5. Previous treatment with crenolanib or prior participation in clinical trial involving crenolanib.