Inclusion Criteria

          1. Subject must sign an ICF

          2. At least 18 years of age

          3. Measurable disease defined as ≥1 measurable nodal lesion (long axis >1.5 cm and short
             axis >1.0 cm) or ≥1 measurable extra-nodal lesion (long axis >1.0 cm) on CT or MRI

          4. ECOG PS score of 0, 1 or 2

          5. Acceptable organ function at screening

          6. CD20-positive NHL at most recent representative tumor biopsy

          7. If of childbearing potential subject must practicing a highly effective method of
             birth control

          8. A man who is sexually active with a woman of childbearing potential must agree to use
             a barrier method of birth control

          9. Arm 1: Newly Diagnosed Documented DLBCL

               -  DLBCL, NOS

               -  "double-hit" or "triple-hit" DLBCL

               -  FL Grade 3B

        Arm 2: R/R FL

        Arm 3: Newly diagnosed, previously untreated FL grade 1-3A

        Arm 4: Documented DLBCL and eligible for HDT-ASCT

          -  DLBCL, NOS

          -  "double-hit" or "triple-hit" DLBCL

          -  FL Grade 3B

        Arm 5: Relapsed Documented DLBCL and ineligible for HDT-ASCT

          -  DLBCL, NOS

          -  "double-hit" or "triple-hit" DLBCL

          -  FL Grade 3B

        Exclusion Criteria

          1. Chemotherapy, radiation therapy, or major surgery within 4 weeks prior to the first
             dose of epcoritamab

          2. Any prior treatment with a bispecific antibody targeting CD3 and CD20.

          3. Treatment with CAR-T therapy within 30 days prior to first dose of epcoritamab

          4. Clinically significant cardiovascular disease

          5. Evidence of significant, uncontrolled concomitant diseases that could affect
             compliance with the protocol or interpretation of results

          6. CNS lymphoma or known CNS involvement by lymphoma at screening as confirmed by MRI/CT
             scan of the brain and, if clinically indicated, by lumbar puncture

          7. Active positive tests for hepatitis B virus or hepatitis C virus indicating acute or
             chronic infection

          8. Known history of seropositivity of human immunodeficiency virus (HIV)

          9. Positive test results for HTLV-1

         10. Suspected active or latent tuberculosis