This study is a Phase II clinical trial designed to evaluate the efficacy and safety of Chidamide as maintenance therapy in high-risk acute myeloid leukemia (AML) patients following stem cell transplantation.

Trial Design: The trial is a single-arm, open-label study. The experimental group plans to enroll 67 patients, while the control group (observation only) also plans to enroll approximately 67 patients, with randomization. All patients must have received induction chemotherapy prior to enrollment and may or may not have received consolidation therapy. The chemotherapy regimen was determined by the treating physician. Patients had received induction and/or consolidation therapy, achieved remission, and underwent stem cell transplantation.

Study Objectives: The study aims to assess the impact of Chidamide maintenance therapy on recurrence-free survival (RFS), overall survival (OS), and the duration of complete remission. The study will also evaluate the tolerability and toxicity profile of this regimen, as well as the effect of maintenance therapy on the dynamics of minimal residual disease (MRD).

Chidamide : 10 mg/day, orally once daily (QD) on days 1-5 per week. During the study, the dose of chidamide may be adjusted at the physician's discretion to 5 mg/day. Each treatment cycle consists of 28 days. Treatment will continue indefinitely, with interruptions and dose adjustments implemented as needed to manage toxicity. Subjects will continue receiving the assigned treatment per investigator assessment for a maximum of 24 months, until documented disease progression, intolerable toxicity, withdrawal of consent, or meeting other protocol-specified criteria for treatment discontinuation (whichever occurs first). Patients who continue to derive clinical benefit, as discussed and agreed upon with the principal investigator, may remain in the study even in the event of relapse (if deemed clinically non-significant).

Inclusion Criteria:

1. AML patients meeting the following conditions (diagnosed per WHO 2022 AML criteria) who achieved first complete remission (CR) with intermediate-/high-risk cytogenetic abnormalities at the time of allogeneic transplantation.
2. Patients must achieve complete remission (CR) post-transplantation.
3. Enrollment must occur between 60 and 100 days after transplantation.
4. Age 18 to 75 years.
5. ECOG performance status 0-1.
6. Serum creatinine < 1.5 × ULN (upper limit of normal).
7. Serum direct bilirubin < 1.5 mg/dL (except in Gilbert's syndrome).
8. ALT and AST < 2.5 × ULN.
9. Ability to understand and provide written informed consent.

Exclusion Criteria:

1. Receipt of any other investigational drugs post-transplantation.
2. FLT3 mutation-positive status.
3. Central nervous system (CNS) involvement.
4. Uncontrolled grade 2-4 graft-versus-host disease (GVHD).
5. Uncontrolled active infection.
6. Known or suspected hypersensitivity to Chidamide or its excipients.
7. Uncontrolled congestive heart failure (CHF) or other concomitant systemic diseases or severe complications that, in the investigator's judgment, would make the patient unsuitable for participation in this study or would significantly compromise the proper assessment of the safety and toxicity of the prescribed regimen.
8. Pregnancy or breastfeeding.
9. Any other condition that, in the investigator's judgment, would make the patient unsuitable for participation in this study.