 This is a phase II, multicenter, single-arm study to assess the safety and feasibility of combining crenolanib with fludarabine and cytarabine chemotherapy in pediatric patients with relapsedrefractory FLT3-mutated AML. Patients will receive up to two courses of salvage chemotherapy with fludarabine, cytarabine, and crenolanib. Response will be assessed between day 29-43 of each course. 