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 pr…