RecruitingPhase 1Drug trialStudy of Cytokine Release Syndrome Prophylaxis and Treatment With Siltuximab Prior to EpcoritamabThe goal of this clinical trial is to is to determine the safety, feasibility and efficacy of siltuximab prophylaxis of cytokine release syndrome and neurotoxicity occurring after epcoritamab subcutaneous administration for participants with large b-cell lymphoma (DLBCL) or follicular lymphoma (FL). Participants will receive siltuximab, prior to the injection of epcoritamab. Epcoritamab is administered in 28 day cycles for one year. After this injection, the physician will continue to watch participants for side effects and follow the condition for a minimum of 60 days.