Efficacy and Safety of VAH as a Bridging Regimen to Allo-HCT in Relapsed/Refractory AML

Inclusion Criteria: * Aged 14 to 70 years (inclusive), regardless of gender; * The diagnosis of AML was confirmed on the basis of bone marrow cytomorphology, immunophenotyping and chromosomal and molecular biology tests; * Relapsed AML: After achieving complete remission (CR), the reappearance of leukemic cells in peripheral blood, or ≥5% blasts in bone marrow (excluding other causes such as bone marrow regeneration after consolidation chemotherapy), or extramedullary infiltration by leukemic cells. Refractory AML: Newly diagnosed cases that are unresponsive after two courses of standard induction therapy; patients who relapse within 12 months after consolidation/intensification therapy post-CR; patients who relapse after 12 months but fail to respond to conventional chemotherapy; patients with two or more relapses; or those with persistent extramedullary leukemia. * With RUNX1::RUNX1T1 AML: Positive measurable residual disease (MRD) on bone marrow flow evaluation after the second consolidation therapy and/or less than a 3-log decrease in the RUNX1::RUNX1T1 fusion gene and diagnostic baseline values; * ECOG score ≤2; HCT-CI score \<3; Aspartate aminotransferase (AST) ≤ 3 times ULN (upper limit of normal, ULN); Alanine aminotransferase (ALT) ≤ 3x ULN; Total serum bilirubin ≤ 1.5 times the upper limit of normal ULN unless the patient has documented Gilbert syndrome; patients with Gilbert-Meulengracht syndrome with bilirubin ≤ 3.0 times the upper limit of normal and direct bilirubin ≤ 1.5 times the upper limit of normal may be included; Serum creatinine ≤ 1.5 times ULN or creatinine clearance ≥ 60 mL/min; Coagulation function: International Normalised Ratio (INR) ≤ 1.5 x ULN, Activated Partial Thromboplastin Time (APTT) ≤ 1.5 x ULN; * Left ventricular ejection fraction (LVEF) ≥50%; Exclusion Criteria: * Allergies or contraindications to any of the drugs in the protocol; * Currently have clinically significant active cardiovascular disease such as uncontrolled arrhythmias, uncontrolled hypertension, congestive heart failure, any grade 3 or 4 heart disease as determined by the New York Heart Association (NYHA) functional class, or a history of myocardial infarction within the 6 months prior to screening; * Serious medical conditions that may limit the patient's participation in this trial (e.g., progressive infection, uncontrolled diabetes); * Active autoimmune diseases such as SLE, rheumatoid arthritis, etc; * Patients with neurological or psychiatric disorders; * The patient is pregnant or breastfeeding; * Those who are unable to understand or comply with the study protocol or are unable to sign the informed consent form. * Other conditions that, in the opinion of the investigator, make the patient otherwise unsuitable for participation in this study;