Bispecific antibody Armed activated T cells exhibit time-dependent co-expression patterns of inhibitory ligands and gene expression programs

Abstract Immunotherapy success has been limited in treating solid tumors. Bispecific antibody Armed activated T cell (BATs) therapy activates, expands, and arms patient T cells ex vivowith bispecific antibodies (BiAb) to produce a “drug” that combines non-MHC restricted cytotoxicity of T cells and specificity of BiAb. BATs therapy promises to improve survival in patients with metastatic breast, prostate, and pancreatic cancer without dose limiting toxicities. However, the anti-tumor potency of BATs varies between patients and decreases with time. Understanding the mechanisms behind this decrease of potency will help identify therapeutic combinations and dosing strategies to maximize patient response. Low effector:target coculture conditions allowing target cell escape from BAT killing were identified. BAT function was measured by anti-tumor cytotoxicity, flow cytometry, and RNA sequencing. Samples were taken at set timepoints to produce a dynamic representation of BAT functional changes in target escape conditions. We observed time-dependent co-expression of inhibitory ligands in BATs, including increased co-expression of PD-1 and LAG3 during the first 24h of coculture, followed by increased co-expression of TIGIT and LAG3 at later timepoints. RNA-seq revealed upregulation of genes associated with T cell dysfunction, including NR4A and checkpoint proteins TIGIT, LAG3, and PD-1, as early as 1 hr in coculture. These findings were integrated into a mechanistic model of BAT-target cell interactions. Our model demonstrated time-dependent emergence of therapeutically targetable inhibitory receptors, suggesting optimizing dosing targets and administration times may improve synergistic immunotherapy combination outcomes.