Twice-per-weekSelinexor, 2 Days Melphalan

Inclusion Criteria: * 1\. Patients with high-risk acute myeloid leukemia (excluding acute promyelocytic leukemia). 2\. Recipients of allogeneic hematopoietic stem cell transplantation (including HLA-matched or mismatched allogeneic transplantation as well as unrelated donor transplantation). 3\. Age ≥ 55 years. 4. Disease status prior to allogeneic transplantation must be complete remission (CRc), confirmed by bone marrow analysis within three days prior to randomization. 5\. Karnofsky Performance Score (KPS) of at least 60. 6. Informed consent must be signed prior to the commencement of the study procedures. If the patient's signature would be detrimental to their treatment due to their medical condition, the informed consent may be signed by a legal guardian or an immediate family member of the patient. Note: \*High-risk AML: ① Patients classified as high-risk according to the ELN 2022 grading criteria. ② AML patients with persistent MRD positivity prior to transplantation. ③ Patients with refractory or relapsed AML. Exclusion Criteria: * 1\. Previous history of hematopoietic stem cell transplantation. 2. Active cardiac disease, defined as one or more of the following: 1. History of uncontrolled or symptomatic angina. 2. Myocardial infarction within the last 6 months prior to study enrollment. 3. History of arrhythmias requiring medication or with clinically significant symptoms. 4. Uncontrolled or symptomatic congestive heart failure (NYHA class \> 2). 5. Ejection fraction below the lower limit of the normal range. 3. Respiratory failure (PaO2 ≤ 60 mmHg). 4. Liver dysfunction (total bilirubin ≥ 3 mg/dL, transaminases \> twice the upper limit of normal). 5\. Renal dysfunction (creatinine clearance rate \< 30 mL/min). 6. Presence of psychiatric disorders or other conditions that prevent cooperation with the study treatment and monitoring requirements. 7\. ECOG performance status of ≥ 4. 8. Uncontrolled or active infection. 9. Any condition that impairs the ability to provide informed consent. 10. Any conditions deemed unsuitable for enrollment by the investigator prior to randomization.