A Study of Subcutaneously Injected Epcoritamab Plus Oral Lenalidomide Tablets 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

Inclusion Criteria:

• Eastern Cooperative Oncology Group Performance status score of 0 to 2.

• Histologically confirmed CD20+ Diffuse Large B-Cell Lymphoma (DLBCL) and documentedin the most recent and representative pathology report, inclusive of the followingaccording to the World Health Organization (WHO) 2022 as per the protocol.

• Must have relapsed or refractory (R/R) disease and have been previously treated withat least 1 line of systemic antineoplastic therapy including anti-CD20mAb-containing combination chemotherapy since DLBCL diagnosis.

• Participant must meet at least 1 of the following criteria:

• Failed prior autologous stem cell transplant (ASCT), defined as relapsed afterASCT or been refractory to high-dose therapy (HDT)-ASCT.

• Not be considered a candidate for ASCT due to age, performance status,comorbidities and/or insufficient response to prior treatment, or have refusedASCT.

• Be ineligible for or unable to receive chimeric antigen receptor T-cell (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 Partial Response (PR)or Complete Response (CR) while on prior CAR-T therapy.

• Must have measurable disease.

• Life expectancy > 3 months on standard of care treatment at the time of enrolling inthe study

Exclusion Criteria:

• Current evidence of primary central nervous system (CNS) lymphoma or known CNSinvolvement by lymphoma including leptomeningeal disease, at screening.

• History of prior treatment with a bispecific antibody targeting CD3 and CD20 orprior treatment with rituximab plus gemcitabine and oxaliplatin (R-GemOx) orgemcitabine and oxaliplatin (GemOx).

• Documented refractoriness to lenalidomide.