Bispecific Antibody-Based Salvage Therapy Followed by CAR-T ± ASCT in R/R Aggressive B-Cell Lymphoma

Inclusion Criteria: 1. Patients with relapsed/refractory aggressive B-cell lymphoma, including the following subtypes: diffuse large B-cell lymphoma (DLBCL), high-grade B-cell lymphoma (HGBL), or transformed large B-cell lymphoma. 2. Relapsed or refractory disease, meeting criteria for one of the following cohorts: Cohort 1 (Relapsed/Refractory Disease): 1. ≥2 prior lines of therapy (including both anti-CD20 monoclonal antibody and anthracycline-based chemotherapy) with documented progression following last treatment; OR 2. Failure of first-line immunochemotherapy (containing anti-CD20 antibody and anthracycline) defined by any of: * Relapse/progression within 12 months of treatment completion; OR * Progressive disease during first-line therapy; OR * Stable disease as best response after 4 cycles; OR * Partial response as best response after 6 cycles. Cohort 2 (Early Treatment Failure): * Persistent metabolic activity (Deauville 5) on PET-CT after 2 cycles of first-line immunochemotherapy; OR * Biopsy-proven residual disease following initial therapy. 3. Age ≥18 years and ≤65 years. 4. Eastern Cooperative Oncology Group (ECOG) performance status ≤2. 5. Hematologic parameters at screening must meet the following (unless due to bone marrow involvement): * Absolute neutrophil count (ANC) ≥1×10⁹/L, * Platelet count (PLT) ≥75×10⁹/L. 6. Biochemical parameters at screening must meet the following: * Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤3× upper limit of normal (ULN); * Total bilirubin (TBIL) ≤1.5×ULN (unless due to Gilbert's syndrome or non-hepatic causes); * Serum creatinine (Cr) ≤2×ULN OR creatinine clearance ≥40 mL/min. 7. Left ventricular ejection fraction (LVEF) within institutional normal range by echocardiography. 8. Baseline oxygen saturation \>92% on room air. 9. Life expectancy ≥3 months as assessed by the investigator. Exclusion Criteria: 1. Confirmed primary central nervous system lymphoma; 2. Prior autologous or allogeneic hematopoietic stem cell transplantation; 3. Active HBV or HCV infection, defined as HBV-DNA or HCV-RNA levels above the upper limit of detection. 4. Uncontrolled comorbidities include infectious diseases, cardiovascular/cerebrovascular disorders, coagulopathies, and connective tissue diseases. 5. History of epilepsy or other central nervous system disorders; 6. Pregnancy or lactation; 7. HIV infection; 8. History of other malignancies unless: 1. Disease-free for ≥5 years, or 2. Previously cured of the following: * Non-melanoma skin cancers (basal cell carcinoma, squamous cell carcinoma, or related localized cutaneous malignancies) * Carcinoma in situ of cervix 9. Other conditions deemed ineligible by investigators.