Subjects will take crenolanib 200mg/m2/day divided in three doses daily (preferably every eight hours), taken orally at least 30 minutes pre or post meal until disease progression, death, or the patient discontinues treatment for adverse events, investigator's judgment, or other reasons. Patients who are able to proceed to allogeneic stem cell transplant will be able to resume crenolanib therapy post-transplant in an attempt to maintain remission.

To determine the response rate to crenolanib.Complete remission (CR) response criteria include a post-baseline bone marrow (BM) biopsy or aspiration % blasts <5%, absolute neutrophil count (ANC) >1×10^9/L and platelet count >100×10^9/L. CRi response included all CR criteria met, except participant did not experience either platelet recovery or ANC recovery. Partial Response (PR) response included a decrease of ≥50% in % blasts in the BM aspirate or biopsy from baseline but >5%. Hematologic improvement (HI) response included erythroid response where Hgb increased ≥ 1.5 g/dL, platelet response where platelets increased ≥ 30 x 10^9/L for patient starting with >20 x 10^9/L platelets or increase from <20 x 10^9/L to >20 x 10^9/L and by at least 100% and neutrophil response where at least 100% increase and an increase >0.5 x 10^9/L. Resistant Disease (RD) was defined as the absence of CR, CRi, CRp, PR or HI.

Participants who had relapsed/refractory AML with FLT3 activating mutations whose leukemia progressed and have a history of prior therapy with one or more FLT3 TKIs received either 200mg/m2 /day crenolanib divided in three doses daily or 100mg TID depending on the version of the protocol at the time of their enrolment. (preferably every eight hours), taken orally at least 30 minutes pre or post meal. Crenolanib was taken orally at the abovementioned doses at least 30 minutes pre or post meal until disease progression, death, or the patient discontinues treatment for adverse events, investigator's judgment, or other reasons. Patients who were able to proceed to allogeneic stem cell transplant were able to resume crenolanib therapy post-transplant in an attempt to maintain remission.

To determine the response rate to crenolanib.Complete remission (CR) response criteria include a post-baseline bone marrow (BM) biopsy or aspiration % blasts <5%, absolute neutrophil count (ANC) >1×10^9/L and platelet count >100×10^9/L. CRi response included all CR criteria met, except participant did not experience either platelet recovery or ANC recovery. Partial Response (PR) response included a decrease of ≥50% in % blasts in the BM aspirate or biopsy from baseline but >5%. Hematologic improvement (HI) response included erythroid response where Hgb increased ≥ 1.5 g/dL, platelet response where platelets increased ≥ 30 x 10^9/L for patient starting with >20 x 10^9/L platelets or increase from <20 x 10^9/L to >20 x 10^9/L and by at least 100% and neutrophil response where at least 100% increase and an increase >0.5 x 10^9/L. Resistant Disease (RD) was defined as the absence of CR, CRi, CRp, PR or HI.

Participants who had relapsed/refractory AML with FLT3 activating mutations who progressed on one or more prior chemotherapy regimens received either 200mg/m2 /day crenolanib divided in three doses daily or 100mg TID depending on the version of the protocol at the time of their enrolment. (preferably every eight hours), taken orally at least 30 minutes pre or post meal. Crenolanib was taken orally at the abovementioned doses at least 30 minutes pre or post meal until disease progression, death, or the patient discontinues treatment for adverse events, investigator's judgment, or other reasons. Patients who were able to proceed to allogeneic stem cell transplant were able to resume crenolanib therapy post-transplant in an attempt to maintain remission.