Venetoclax Combining Chidamide and Azacitidine (VCA) in the Treatment of R/R AML

Inclusion Criteria: * Age ≥18 * Relapsed and refractory patients with acute myeloid leukemia via morphology and immunology * ECOG：0-2 * Life expectancy ≥ 3 months * Adequate laboratory parameters during the screening period as evidenced by the following: 1. Creatinine clearance≥30 mL/min and serum Creatinine ≤ 160µmol/L 2. ALT and AST ≤ 3 × upper limit of normal (ULN) 3. Able to understand and sign an informed consent form (ICF). Exclusion Criteria: * Diagnosis of acute promyelocytic leukemia (APL) * Central nervous system leukemia * Uncontrolled or significant cardiovascular disease, including any of the following: 1. Bradycardia of less than 50 beats per minute, unless the subject has a pacemaker; Diagnosis of or suspicion of long QT syndrome (including family history of long QT syndrome); 2. Systolic blood pressure ≥180 mmHg or diastolic blood pressure ≥110 mmHg; History of clinically relevant ventricular arrhythmias (eg, ventricular tachycardia, ventricular fibrillation, or Torsade de Pointes); 3. History of second (Mobitz II) or third degree heart block (subjects with pacemakers are eligible if they have no history of fainting or clinically relevant arrhythmias while using the pacemaker); 4. History of uncontrolled angina pectoris or myocardial infarction within 6 months prior to Screening; 5. History of New York Heart Association Class 3 or 4 heart failure; 6. Complete left bundle branch block; 7. Known history of left ventricular ejection fraction (LVEF) ≤45% or less than the institutional lower limit of normal; * Active acute or chronic systemic fungal, bacterial, or viral infection not well controlled by antifungal, antibacterial or antiviral therapy; * Suffered from other non-myeloid malignancies within 2 years, except adequately treated non-melanoma skin cancer, curatively treated in-situ disease, or other solid tumors curatively treated with no evidence of disease * Females who are pregnant or breastfeeding; * Mental disorders that hinder research participation * Previous solid organ transplantation (SCT treatment is allowed in advance, but if the patient has GVHD or is still receiving immunosuppression/GVHD treatment, it is not allowed) * Any other situation where the investigator believes that the patient should not participate in this trial