Background:Patients with relapsed/ refractory (R/R) FLT3-internal tandem duplication positive (FLT3-ITD+) acute myeloid leukemia (AML) have limited treatment options and poor prognosis. Clifutinib is a novel, highly selective, oral FLT-3 inhibitor with potent activity against FLT3-ITD(+) leukemic models both in vitroand in vivo. This study is a first-in-human study of clifutinib, with the purpose of evaluating the safety, tolerability, efficacy, and pharmacokinetic (PK) profile in Chinese patients with R/R FLT3-mutated AML (NCT04827069).