Epcoritamab (Epcor)-Containing Combination Salvage Therapy Followed by ASCT & Epcor Consolidation in Patients With Relapsed LBCL

The goal of this clinical trial is to evaluate clinical efficacy of incorporating Epcoritamab into the salvage treatment routine for relapsed-refractory aggressive B-cell lymphoma, followed by autologous stem-cell transplantation (ASCT) and consolidation Epcoritamab. The main questions it aims to answer are: * Will the addition of epcoritamab to intensive salvage chemotherapy be safe and increase the proportion of patients with relapsed or refractory (R/R) large B-cell lymphoma who achieve a complete remission prior to planned transplant? * Is consolidation epcoritamab after ASCT deliverable and safe? * Will consolidation epcoritamab will result in improved clearance of molecularly detectable residual disease? * Will the combination of pre- and post-ASCT epcoritamab lead to higher rates of progression-free survival (PFS) and event free survival (EFS) at 12 months compared to historical estimates in this population. Participants will undergo three phases in this trial: 1. Epcoritamab-Salvage treatment: consists of 3 cycles of R-DHAOx (rituximab, dexamethasone, cytarabine, oxaliplatin) plus Epcoritamab 2. ASCT: Pre-autograft eligibility assessment for ASCT will be performed according to local practice. ASCT may be administered at local referring centre and will follow local standard operative procedures. 3. Consolidation treatment: consists of six 28-day cycles of subcutaneous Epcoritamab, commencing 6 - 12 weeks post ASCT.