Blinatumomab Combined With Venetoclax as Maintenance Therapy After Allo-HSCT in High-risk Ph Negative Acute B-cell Lymphoblastic Leukemia

Inclusion Criteria: * Demographics : Patients aged 14-65 years, regardless of gender or race. * Diagnosis : Confirmed Ph-negative acute B-cell lymphoblastic leukemia (Ph- B-ALL) through bone marrow cytomorphology, cytochemistry, immunophenotyping, chromosomal analysis, and genetic mutation testing, with CD19 surface antigen expression. * Risk Stratification : High-risk B-ALL (per NCCN 2024.V2 guidelines) or Standard-risk B-ALL with no pre-transplant remission or Standard-risk B-ALL in first complete remission (CR1) with measurable residual disease (MRD) positivity or Standard-risk B-ALL with ≥CR2 or B-ALL patients receiving reduced-intensity or non-myeloablative conditioning. * Transplant Eligibility : Scheduled for allogeneic hematopoietic stem cell transplantation (allo-HSCT) with a suitable donor meeting: HLA-identical sibling donor or Unrelated donor (HLA 9-10/10 high-resolution matched) or Haploidentical related donor. * HCT-CI Score : ≤2 (Hematopoietic Cell Transplantation-Specific Comorbidity Index). * ECOG Performance Status : ≤2. * Organ Function : Serum creatinine ≤1.5×ULN Cardiac ejection fraction ≥50% Baseline SpO₂ \>92% Total bilirubin ≤1.5×ULN; ALT/AST ≤2.0×ULN Pulmonary DLCO (hemoglobin-adjusted) ≥40% and FEV1 ≥50% * Post-Transplant Recovery : Full donor chimerism Platelet count \>50×10⁹/L Absolute neutrophil count \>1.0×10⁹/L Hemoglobin \>80g/L - Informed Consent : Patient and legal guardian must provide written informed consent, comply with treatment protocols, follow-up visits, and laboratory assessments. Exclusion Criteria: * Prior Malignancy : History of malignancy other than acute lymphoblastic leukemia within 5 years, except for adequately treated cervical carcinoma in situ, basal or squamous cell skin cancer, localized prostate cancer post-radical resection, or ductal carcinoma in situ post-resection. * MRD-Negative B-ALL : Standard-risk B-ALL with MRD-negative status pre-transplant (per NCCN 2024.V2). * Disease Activity : Relapse of primary disease or CR/MRD positivity (≥0.01%) confirmed by bone marrow re-evaluation within 1 week before maintenance therapy. * T-Cell Deficiency : Absolute CD3+ T-cell count ≤0.5×10⁹/L prior to maintenance therapy. * Active GVHD : Concurrent acute/chronic GVHD requiring systemic immunosuppressive treatment. * Unstable Systemic Diseases : Including but not limited to: * Unstable angina or cerebrovascular accident/transient ischemic attack (within 3 months) * Myocardial infarction (within 3 months) * Congestive heart failure (NYHA Class ≥ III) * Post-pacemaker implantation with severe arrhythmia requiring medication * Uncontrolled hepatic/renal/metabolic diseases * Pulmonary hypertension * Active Infection : Uncontrolled infections requiring intravenous antibiotics. HIV : Positive human immunodeficiency virus status. Hepatitis : Active HBV/HCV requiring antiviral therapy. * Psychiatric Conditions : Mental disorders or inability to provide informed consent. * Substance Abuse : Drug addiction or chronic alcoholism affecting trial evaluation. * Reproductive Status : Pregnant/breastfeeding females Fertile patients unwilling to use contraception during treatment and 12 months post-treatment \- Other : Conditions deemed inappropriate by investigators.