This investigator-initiated, prospective, single-arm, multicenter clinical trial aims to evaluate the efficacy and safety of BEBT-908 (a HDAC/PI3Kα inhibitor provided by BeBetter Med Inc ,Guangzhou, China) combined with chemotherapy in patients with MEF2D-rearranged and pre-B acute lymphoblastic leukemia who are in complete remission (CR) but remain minimal residual disease (MRD) positive.

MEF2D-rearranged and pre-B acute lymphoblastic leukemia patients achieving CR after chemotherapy and have MRD+ will be given BEBT-908 (12.3 mg/m2) combined with Mini-Hyper-CVD and Mini-MTX/Ara-C chemotherapy for two cycles.

After two cycles, If MRD negativity is achieved and the patient is eligible for transplantation, hematopoietic stem cell transplantation will be performed; if MRD negativity is achieved but the patient is not suitable for transplantation, an additional six courses of BEBT-908-based combination chemotherapy will be given. Patients who fail to reach MRD negativity will be withdrawn from the study.

A total of 23 patients will be enrolled

Inclusion Criteria:

1. The subject voluntarily agrees to participate in this trial and signs the informed consent form, and is able to understand and comply with all study requirements;
2. Age between ≥18 and ≤75 years at screening, with no gender restrictions;
3. Meets the diagnostic criteria for BCP-ALL (according to the 2022 WHO classification) and fulfills any one of the following conditions:

1) Positive for MEF2D rearrangement 2) Philadelphia chromosome negative and consistent with a Pre-B immunophenotype (according to the EGIL 1995 immunophenotyping criteria, cytoplasmic IgM+); 4. Diagnosed with BCP-ALL in complete remission but with positive minimal residual disease (MRD), defined as: achieving hematologic complete remission (CR) after treatment (bone marrow blast count <5% by morphology) but with positive MRD (MRD ≥10-⁴, as detected by flow cytometry and/or PCR); 5. ECOG performance status score of 0-2 at screening; 6. Expected survival is more than 3 months. 7. Satisfactory organ function, meeting the following criteria:

1. Serum creatinine ≤1.5 times the upper limit of normal（ULN）；
2. Left ventricular ejection fraction (LVEF) >50%; 3）Total bilirubin ≤2 times ULN；Alanine aminotransferase (ALT) ≤3 times ULN; Aspartate aminotransferase (AST) ≤3 times ULN

Exclusion Criteria:

1. Known allergy to the study drug or its excipients.
2. Presence of severe and/or uncontrolled infection.
3. Severe cardiac disease, including: heart failure classified as New York Heart Association (NYHA) functional class III or IV; history of acute myocardial infarction within 6 months prior to screening; uncontrolled arrhythmias or electrophysiological abnormalities such as sick sinus syndrome, third degree atrioventricular block, QTc > 480 ms, ventricular tachycardia, persistent atrial fibrillation with rapid ventricular response, etc.; or severe structural cardiac abnormalities on echocardiography or left ventricular ejection fraction (LVEF) < 50 %.
4. Primary central nervous system diseases, including cerebrovascular accident, intracranial infection, etc., within six months before screening.
5. Severe primary pulmonary diseases, including significant impairment of pulmonary ventilation/diffusion function, respiratory failure, etc.
6. Severe hepatic impairment: total bilirubin (TB), gamma glutamyl transferase (γGT), ALT, or AST > 3 times ULN at baseline or after hepatoprotective therapy; or conditions such as severe hepatitis, cirrhosis, etc.
7. Severe renal impairment: serum creatinine > 1.5 × ULN; or uncorrected acute kidney injury.
8. Acute or chronic pancreatitis, with serum amylase > 3 × ULN.
9. Pregnancy or lactation.
10. History of other prior malignancies that may affect protocol compliance or interpretation of study results.
11. Diagnosed major psychiatric disorder or predisposition to psychiatric illness that would significantly impair the ability to participate in the clinical study.
12. Any other condition deemed by the investigator as unsuitable for study enrollment.