Novel Nanobody-161 binds Tumor necrosis factor receptor 2 (TNFR2) to exert an anti-tumor effect but does not block TNFα-binding

Background: Tumor necrosis factor receptor 2 (TNFR2) is exclusively expressed on regulatory T cells (Tregs) and many cancer cells indicating its potential as a therapeutic target. A novel anti-cancer mechanism for targeting TNFR2 is presented and clinical potential discussed. Methods: A novel humanized anti-TNFR2 nanobody, Nanobody-161, was identified from the Sanyou Bio Super Trillion Antibody Library in the current work. The non-blocking effect of Nanobody-161 in TNFα-TNFR2 signaling was then investigated. A transgenic mouse model was established to investigate its anti-tumor activity. The crystal structure of the complex with TNFR2 was also analyzed. Results: Nanobody-161 had antitumor activity in a transgenic mouse model, reducing tumor weight by 5-fold at a dose of 7.5 mg/kg and inhibited TNFα-TNFR2 signaling in HEK293 cells overexpressing human TNFR2 with 10-fold greater potency than traditional antagonists. Nanobody-161 did not disrupt TNFα-induced Treg proliferation in peripheral blood mononuclear cells. Nanobody-161 mediated Fc-dependent CD8⁺ T cell activation and TNFR2⁺ Tregs in the tumor microenvironment were depleted by antibody-dependent cell-mediated cytotoxicity (ADCC). The structure of Nanobody-161 in complex with TNFR2 was determined at 2.9 Å resolution and epitopes of TNFR2 CRD2 and CRD3 were identified. Nanobody-161 may inhibit TNFR2 oligomerization but did not block TNFα binding. Conclusion: Nanobody-161 is a novel non-blocking TNFR2-antogonist that affects tumor growth without causing immunosuppression, and is expected to be a promising candidate for antitumor therapy.