Molecular Features of Response and Resistance to Glofitamab, a T-Cell Engager for treatment of Large B-Cell Lymphoma.

T-Cell Engagers (TCEs) have recently transformed the therapeutic landscape of hematological malignancies, including relapsed or refractory B-cell non-Hodgkin lymphoma (R/R B-NHL). However, the variability in patient responses underscores the need for a deeper mechanistic understanding of the factors driving efficacy. Immune cell composition and T-cell functional states are emerging as critical determinants of immunotherapy outcomes. Recent advances in scRNA-seq technologies have enabled high-resolution characterization of T-cell states, revealing a spectrum from highly activated effectors to exhausted or dysfunctional subsets within the tumor microenvironment (TME). In this study, we conducted longitudinal scRNA-seq analyses and functional assessments of peripheral blood immune cells (PBMC) from glofitamab-treated R/R B-NHL patients, achieving complete metabolic responders (CMR) or progressive metabolic disease (PMD). Our findings reveal that the maintenance of naive-like ("fresher") T-cell states (particularly the fresher cytotoxic T cells) at early timepoints is associated with clinical efficacy. In line with molecular data, T cells from responders exhibited enhanced functional activity compared to non-responders. Furthermore, the analysis of patient PBMCs and intra-tumor T cells from preclinical tumor models after consecutive glofitamab treatments revealed sustained functional activity, underscoring the long-term durability of T-cell responses. Combination of glofitamab with 4-1BB co-stimulation translated into increased proportions of intra-tumor T cells having a "fresher", naive-like phenotype, ultimately leading to stronger anti-tumor efficacy. Taken together, our findings underscore the therapeutic relevance of "fresher" naive-like T-cell states and the potential of leveraging 4-1BB co-stimulation to overcome TCE resistance and improve clinical responses in aggressive lymphomas.