Response to Mosunetuzumab in Patients with B-Cell Lymphomas Relapsed or Refractory after CAR-T Cell Therapy Is Associated with Changes in Lymphocyte Counts

Introduction: Mosunetuzumab is a CD20/CD3 bispecific antibody that redirects endogenous T cells to kill malignant B cells by concomitantly binding to CD3 on T cells and CD20 on B cells. A multicenter phase I/II study evaluating mosunetuzumab in relapsed/refractory (r/r) non-Hodgkin lymphomas, including patients r/r after chimeric antigen receptor-modified T-cell therapies (CAR-T), was the basis for FDA approval for mosunetuzumab in follicular lymphoma (NCT02500407; Budde et al. Lancet Oncol 2022). We retrospectively assessed the impact of mosunetuzumab on lymphocyte counts and CAR T cells in responding and non-responding patients.