A Study of Subcutaneously Injected Epcoritamab Plus Oral Lenalidomide Capsules Compared to Intravenously (IV) Infused Rituximab Plus IV Infused Gemcitabine and IV Infused Oxaliplatin in Adult Participants With Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Prior treatment

• Prior treatment with a bispecific antibody targeting CD3 and CD20 or prior treatment with R-GemOx or GemOx.
• Lenalidomide exposure within 12 months prior to screening or history of documented refractoriness to lenalidomide with refractoriness defined as: • best response SD or PD, or • PD within 6 months of completion of the therapy
• Best response to prior CAR-T therapy of SD or PD. Subject should not have received any treatment with CAR-T therapy within 90 days prior to randomization; any CAR-T related toxicity should have been resolved for at least 30 days.

Other illness

• Current evidence of primary CNS lymphoma or known CNS involvement by lymphoma including leptomeningeal disease, at screening
• Current autoimmune disease requiring immunosuppressive therapy except for up to 20 mg daily prednisone or equivalent.

• Subject must have histologically confirmed CD20+ DLBCL and documented in the most recent representative pathology report, inclusive of the following according to the 5th edition of the WHO (2022) Classification of Haematolymphoid Tumours: Lymphoid Neoplasms: • DLBCL, NOS including de novo or histologically transformed from an earlier diagnosis of FL or MZL • DLBCL/HGBCL with MYC and BCL2 rearrangements • Follicular large B-cell lymphoma (FLBL; previously FL Grade 3B) • T-cell/histiocyte-rich large B-cell lymphoma • Epstein Barr Virus-positive DLBCL
• Subject must have R/R disease and have been previously treated with at least 1 line of systemic antineoplastic therapy including anti-CD20 mAb-containing combination chemotherapy since DLBCL diagnosis. Note: Relapsed disease is defined as disease that has recurred ≥ 6 months after completion of therapy. Refractory disease is defined as disease that either progressed during therapy, failed to achieve an objective response to prior therapy, or progressed within 6 months after completion of therapy (including maintenance therapy).
• Subject must meet at least 1 of the following criteria: • Failed prior ASCT, defined as relapsed after ASCT or been refractory to ASCT • Not be considered a candidate for ASCT due to age, performance status, comorbidities and/or insufficient response to prior treatment, or have refused ASCT • Be ineligible for or unable to receive CAR-T meeting at least 1 of the following criteria: • Unable to receive CAR-T therapy due to fitness and/or comorbidity • Lymphocyte apheresis failure • Unwilling to receive CAR-T therapy • Unable to receive CAR-T therapy due to financial, geographic, insurance, access, and/or manufacturing constraints • Relapsed/progressed after having achieved at least a PR or CR while on prior CAR-T therapy
• Subject must have measurable disease defined as: • ≥ 1 measurable nodal lesion (long axis > 1.5 cm) or ≥ 1 measurable extra-nodal lesion (long axis > 1.0 cm) on CT or MRI AND •F-FDG PET scan positive
• Subject must have an Eastern Cooperative Oncology Group Performance status score of 0 to 2.