Donor‐Derived T‐Cell Redirection With Epcoritamab Achieving Complete Response After Early Post‐Allo‐HSCT Relapse of DLBCL

ABSTRACT Background Epcoritamab, a bispecific CD3×CD20 antibody, offers a promising treatment for relapsed diffuse large B‐cell lymphoma (DLBCL). Its efficacy and safety after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) remain unclear. Case Report In a 64‐year‐old man with relapsed DLBCL, epcoritamab showed limited efficacy, achieving stable disease prior to allo‐HSCT; nevertheless, re‐administration after donor T‐cell engraftment resulted in a complete response without severe graft‐versus‐host disease or cytokine release syndrome. Conclusions This observation suggests that donor‐derived T‐cell redirection with epcoritamab may enhance antitumor efficacy while maintaining safety in the post‐transplant setting, supporting its potential as a salvage therapy for relapsed DLBCL post‐allo‐HSCT.