MRD-Directed Consolidation With Epcor-only or Epcor-R2 Post Anti-CD19 CAR TCell Therapy for Large B-Cell Lymphoma

Inclusion Criteria 1. Age ≥ 16 years old at the time of signing the patient information and consent form (PICF) 2. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 3. A diagnosis of relapsed/refractory large B-cell lymphoma 4. Received Therapeutic Good Administration (TGA) approved anti-CD19 CAR T-cell therapy as the most recent large B-cell lymphoma treatment. 5. Partial metabolic response (PMR) or complete metabolic response (CMR) as per the Lugano criteria on the most recent PET/CT performed at any point between Day +25 and Day +100 post CAR T-cell infusion, when compared with the most recent PET/CT prior to CAR T-cell infusion. 6. MRD positive by a ctDNA assay on a blood sample taken at any point between Day +25 and Day +100 post CAR T-cell infusion. 7. Adequate haematological function documented within 7 days prior to randomisation 8. Adequate cardiac function. 9. Adequate renal function, documented within 7 days prior to randomisation 10. Adequate hepatic function documented within 7 days prior to randomisation 11. Complete resolution of cytokine release syndrome (CRS), macrophage-activation syndrome (MAS)/haemophagocytic lymphohistiocytosis (HLH) or immune effector cell-associated neurotoxicity syndrome (ICANS) related to prior CAR T-cell therapy. 12. Female patients of childbearing potential (FCBP) must be willing to follow the contraceptive method/procedure as outline in the PICF 13. Sexually active males must agree to use a condom during sexual contact with a pregnant female or a FCBP for the course of the study through to 4 months after the last dose of epcoritamab, even if he has undergone a successful vasectomy 14. Women must agree not to donate eggs (ova, oocytes) for the purposes of assisted reproduction. Men must also not donate sperm during the trial and for 4 months after receiving the last dose of epcoritamab 15. The patient understands the purpose of the trial and procedures required for the trial which includes compliance with the protocol requirements and restrictions listed in the PICF and in this protocol Exclusion Criteria 1. A history of Grade 4 CRS or ICANS related to prior CAR T-cell therapy 2. Patients whose lymphoma is known to be CD20 negative on the most recent biopsy prior to CAR T-cell therapy 3. Ongoing active bacterial, viral, fungal, mycobacterial, parasitic, or other infection requiring systemic treatment 4. Progression or relapse within 3 months after a regimen containing a bispecific antibody targeting CD3 and CD20 5. A diagnosis of primary central nervous system (CNS) lymphoma 6. Active secondary CNS involvement of lymphoma at time of screening 7. A known history or current autoimmune disease or other diseases resulting in permanent immunosuppression 8. Known cognitive impairment would place the patient at increased risk of complications from ICANS 9. A known history of hepatitis B serology consistent with acute or chronic infection 10. A known history of hepatitis C serology consistent with acute or chronic infection 11. A known history of testing positive for human immunodeficiency virus (HIV) 12. Any comorbidity conferring a life expectancy of \< 5 years (e.g., second malignancy) or that in the opinion of the site investigator may significantly impact the ability to complete the trial therapy and follow-up or affect the interpretation of results 13. Exposed to live or live attenuated vaccine within 4 weeks prior to signing the PICF. 14. Women who are pregnant or lactating 15. Known hypersensitivity to epcoritamab, lenalidomide, rituximab, tocilizumab or their excipients 16. Presence of any psychological, social or geographical or other condition for which participation would not be in the best interest of the patient