• Primary CNS lymphoma or CNS involvement • Known past or current malignancy other than inclusion diagnosis • Autoimmune or other diseases resulting in permanent immunosuppression or immunosuppressive therapy • Seizure disorder requiring therapy (eg, steroids or anti-epileptics) • Any prior therapy with an investigational bispecific antibody targeting CD3 and CD20 • Prior treatment with CAR T therapy within 30 days of first epcoritamab administration • Eligible for curative intensive salvage therapy followed by high-dose chemotherapy with HSCT rescue • Autologous HSCT within 100 days of first epcoritamab administration, or any prior allogeneic HSCT or solid organ transplantation • Active hepatitis B or C infection (evidence of prior hepatitis B virus but PCR-negative is permitted) or known HIV infection