CLAG+VEN vs CLAG in the Treatment of Relapsed/Refractory AML

Inclusion Criteria: 1. Diagnosed of AML according to the World Health Organization (WHO) classification. 2. All patients should aged 18 to 65 years. 3. Diagnosed of relapsed and refractory AML, according to The guidelines for diagnosis and treatment of relapse /refractory acute myelogenous leukemia in China（2023） 4. Diagnostic criteria for relapsed AML: Leukemia cells reappear in the peripheral blood or primitive cells in the bone marrow ≥ 5% (excluding other reasons such as bone marrow regeneration after consolidation chemotherapy) after CR, or leukemia cell infiltration appears outside the marrow. 5. Diagnostic criteria for refractory AML: The newly diagnosed patients who failed to respond to two courses of standard treatment; Patients who relapsed within 12 months after consolidation intensive therapy; Patients who relapsed after 12 months and failed to respond to conventional chemotherapy; Patients with two or more recurrences; Patients with persistent extramedullary leukemia. 6. The score of Eastern Cooperative Oncology Group (ECOG) is 0-2. 7. Renal function: creatinine clearance rate ≥ 30ml/min. 8. Liver function: ALT\<5 times normal value, bilirubin\<3 times normal value. 9. Predicted survival ≥ 3 months. 10. Able to accept oral Venetoclax. 11. Sign an informed consent form and be able to understand and follow the procedures required by this protocol. Exclusion Criteria: 1. Diagnosed of acute promyelocytic leukemia (AML-M3) 2. Patients with central nervous system (CNS) invasion. 3. Cardiac function \< grade 2. 4. Known human immunodeficiency virus (HIV) infection. 5. Other clinically significant uncontrolled conditions, including but not limited to: a. uncontrolled or active systemic infections (viruses, bacteria, or fungi); b. Chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) requiring treatment; c. Secondary tumors requiring active treatment. 6. Allergy to experimental drugs. 7. Pregnant and lactating women. 8. Patients who ineligible for the study according to the investigator's assessment.