A TNFR2 biparatopic antagonist reverses immune suppression through a crosslinking-resistant and ADCC- independent mechanism

Tumor necrosis factor receptor 2 (TNFR2) is a promising immunotherapeutic target due to its high upregulation on immunosuppressive populations, like regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). The clinical efficacy of conventional bivalent TNFR2 antagonists, such as BI1808, is fundamentally constrained by a heavy reliance on Fc-mediated effector functions and a significant risk of ‘agonistic conversion’ upon crosslinking within the tumor microenvironment. To overcome these liabilities, we engineered Duo1, a novel biparatopic antagonist that enables simultaneous, monovalent engagement of two distinct TNFR2 epitopes. Biophysical analysis confirmed Duo1 forms stable 1:1 complexes with TNFR2 with high-affinity (KD = 0.165 nM), structurally locking the target to prevent the receptor oligomerization required for agonistic signaling. Crucially, while conventional bivalent frameworks convert into potent agonists upon cross-linking, Duo1 maintains absolute, durable antagonism regardless of FcγR engagement. Functionally, Duo1 potently suppressed Treg differentiation and reversed Treg-mediated immunosuppression in vitro without impairing CD8+ effector T cell or CD4+ conventional T cell function.. In a TNFR2-humanized MC38 syngeneic model, Duo1 mediated significant, dose-dependent tumor growth inhibition comparable to benchmark BI1808. Notably, this anti-tumor efficacy was fully preserved in an effector-silent (PGLALA) variant, confirming that its therapeutic mechanism operates through pure antagonistic signaling blockade, independent of Fc-mediated effector functions. Furthermore, treatment with Duo1 significantly remodeled the tumor microenvironment, markedly reducing immunosuppressive populations and increasing the intratumoral CD8+/Treg ratio. By uncoupling anti-tumor activity from both the risks of cross-linking induced agonistic conversion and a dependence on immune cell mediated effector function, Duo1 represents a highly superior next-generation immunotherapeutic paradigm for TNFR2-rich, immunosuppressive malignancies.