Epcoritamab for the Treatment of Relapsed or Refractory Post Transplant Lymphoproliferative Disorders

Inclusion Criteria: * Written informed consent obtained to participate in the study and Health Insurance Portability and Accountability Act (HIPAA) authorization for release of personal health information to the sponsor, sites, and relevant study organizations. * Age ≥ 18 years at the time of consent. * Karnofsky scale ≥ 50% or Eastern Cooperative Oncology Group (ECOG) ≤ 2. * Histological evidence of B-cell PTLD (any histologic subtype) following solid organ transplantation; expresses CD20; with or without EBV association. * Treatment failure of immunosuppression reduction (ISR). NOTE: if ISR was deemed not feasible by treating physician, ISR treatment failure may be waived. * Treatment failure of rituximab or rituximab plus any concurrent or sequentially administered chemotherapy regimen. * Measurable disease of \> 1.5 cm in diameter and/or bone marrow involvement. * Subjects having undergone heart, lung, liver, kidney, pancreas, small intestine transplantation or a combination of the organ transplantations mentioned. * HIV infection is allowed if viral load is undetectable at time of enrollment, CD4+ count \> 200 cells/uL, and subject remains on anti-viral therapy. * Resolution of toxicities from prior therapy to a grade that does not contraindicate trial participation in the opinion of the investigator. * Expected survival greater than 60 days. * Absolute neutrophil count 1.0 ≥ x 10\^9/L. * Platelets 50 ≥ x 10\^9/L. * Creatinine clearance (mL/min) ≥ 30 mL/min - Cockcroft-…