A Study of Epcoritamab and Ibrutinib in People With Central Nervous System Lymphoma (CNSL)

Inclusion Criteria: * \>/= 18 years of age on the day of consenting to the study. * Histologically documented DLBCL at enrolling institution (biopsy or CSF samples in PCNSL; biopsy of CNS or non-CNS sample in SCNSL) * Participants must have an ECOG performance status of 0, 1, or 2. * Participants must have adequate bone marrow and organ function shown by: * Absolute neutrophil count (ANC) ≥ 1 x 109/L * Platelets ≥ 75 x 109/L and no platelet transfusion within the past 21 days prior to study consent * Hemoglobin (Hgb) ≥ 8 g/dL and no red blood cell (RBC) transfusion within the past 21 days prior to study consent * International Normalized Ratio (INR) ≤ 1.5 and PTT (aPTT) ≤ 1.5 times the upper limit of normal (unless receiving anticoagulation) * Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 times the upper limit of normal * Serum bilirubin ≤ 1.5 times the upper limit of normal; or total bilirubin ≤ 3 times the upper limit of normal with direct bilirubin within the normal range in patients with well documented Gilbert Syndrome. * Creatinine clearance (CLCr) ≥ 30 ml/min (based on the following formular Creatinine clearance= ((140-age)\*wt)/(creatinine\*72); multiply by 0.85 for women) * Women of reproductive potential must agree to use highly effective methods of birth control during the period of therapy and for 30 days after the last dose of the study drug. Men who are sexually active must agree to use highly effective contraception dur…