Clinical Outcomes and Exploratory Longitudinal CTL/Vβ Repertoire Remodeling in Patients with Relapsed or Refractory Large B-Cell Lymphoma and Follicular Lymphoma Treated with Epcoritamab

Epcoritamab, a subcutaneous CD3×CD20 bispecific antibody, has shown substantial activity in relapsed or refractory (R/R) B-cell lymphomas, but the immunological correlates of durable remission and treatment discontinuation remain unclear. We retrospectively analyzed 21 consecutive patients who initiated epcoritamab at our institution between 1 December 2023 and 31 December 2025, including 17 with R/R large B-cell lymphoma (LBCL) and 4 with R/R follicular lymphoma (FL). Clinical follow-up was updated through 18 May 2026. Serial cytotoxic T lymphocyte (CTL) subset and T-cell receptor (TCR) Vβ repertoire analyses were performed in selected cases. Among response-evaluable patients, the overall response rate was 9/14 in LBCL and 4/4 in FL. Median overall survival was 431 days in LBCL and 431.5 days in FL. Progression-free survival was analyzed descriptively because of the small sample size and substantial censoring. A patient with clinically and radiologically suspected central nervous system relapse of LBCL achieved radiological complete remission after epcoritamab treatment. In two LBCL and one FL case in whom epcoritamab was electively discontinued after complete remission, Vβ-skewed CTL populations were observed, and total memory CTLs exceeded total effector CTLs at discontinuation. These exploratory findings suggest that epcoritamab treatment may be associated with longitudinal remodeling of CTL subsets and Vβ-skewed CTL populations in selected responders. The potential relevance of these immunological patterns to durable response and treatment discontinuation should be validated in larger prospective cohorts with functional and sequence-based T-cell analyses.