It is open-label, dose escalation study designed to characterize the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of orally administered MRX2843 as a single agent given daily for 28 days.~The study includes two parts, Phase I and Phase II, and is carried out in three phases. The Phase I clinical study is divided into two phases: the dose escalation study (Ia) and the expanded enrollment study (Ib). The third phase is the phase II research phase, which is designed based on phase I clinical results.~Phase Ia：Cohorts of 3 patients receive MRX2843 until dose limiting toxicity is noted (DLT). At that point cohorts will expand to 6 patients until MTD is determined.~Phase Ib/ II：According to the relevant data on safety and effectiveness, expand the enrollment of FLT3 mutation relapsed/refractory AML patients at the appropriate dose
Patients will receive oral MRX2843 for 28 days to study the side effects, tolerability and best dose for treating relapsed or refractory acute myeloid leukemia With FLT3 Mutations.