Peripheral CD4+ T-Cell Reserve as a Potential Biomarker of CD20 × CD3 Bispecific Antibody Outcomes and BTK Inhibitor-Associated Immune Modulation in B-Cell Lymphoma.

Bispecific antibodies (BsAbs) targeting CD20 × CD3 have achieved remarkable efficacy in relapsed or refractory (R/R) B-cell lymphoma, yet clinical responses remain heterogeneous and predictive biomarkers are lacking. We retrospectively evaluated associations between peripheral immune profiles and outcomes in 40 patients treated with CD20 × CD3 BsAbs and explored BTK inhibitor-associated immune changes using a paired BTK inhibitor cohort, functional assays, mouse models, and single-cell RNA sequencing. Higher baseline CD4+ T-cell counts correlated with superior response rates and prolonged progression-free survival, whereas CD8+ counts showed no association. Elevated CD4+ T-cell levels were linked to increased activation of effector CD8+CD28+ T cells and greater induction of IL-2 and IFN-γ following treatment. Across paired clinical samples and experimental models, BTK inhibition was associated with CD4+ T-cell expansion and enhanced T/NK-cell proliferative and cytotoxic signatures. In an exploratory real-world observation, three patients received BTK inhibition before glofitamab; all achieved complete responses, with two remaining in remission at data cutoff and one relapsing after 8.4 months. These findings identify peripheral CD4+ T-cell reserve as a potential biomarker associated with BsAb outcomes and provide a rationale for further investigation of BTK inhibitor-mediated immune modulation in BsAb treatment strategies.