Abstract 495: TNFR2 and PD-1/PD-L1/TNFR2 humanized mice aiding exploration of combination strategies to overcome tumor immune escape mechanisms

Tumor necrosis factor receptor 2 (TNFR2), also known as tumor necrosis factor receptor superfamily member 1B (TNFRSF1B), is a transmembrane protein, which can mediate both pro- and anti-inflammatory activities of T cells. TNFR2 is mainly expressed on the surface of activated effector T cells and regulatory T cells (Tregs) and promotes proliferation and survival of Tregs through nuclear factor kappa B (NF-κB). Blockade of TNF-TNFR2 interaction with monoclonal antibodies can inhibit the activation of Tregs, possibly resulting in inhibition of their function and/or reduction of their numbers. Yet, until recently the potential of TNFR2 as a therapeutic target for cancer therapy has been underappreciated. Discovery of anti-TNFR2 antibodies, developed to inhibit NF-κB driven growth, has revived excitement for the use of TNFR2as a cancer therapy target and stressed the demand for suitable pre-clinical models to evaluate the safety and efficacy of TNFR2-targeted therapeutics. Biocytogen has generated a humanized TNFR2 mouse model for both in vitro function validation of signaling pathways and in vivo efficacy evaluation of TNFR2 antibodies. In this model, the exons 2~6 of mouse Tnfrsf1b gene which encode the extracellular domain were replaced by human TNFRSF1B counterparts. In the humanized mouse, human TNFR2 was detectable on Tregs in the spleen and the anti-human TNFR2 antibodies associated well with the splenocytes. In addition, anti-human TNFR2 antibodies bound well to CD3+ T cells and inhibited tumor growth. Furthermore, Biocytogen has also generated PD-1/PD-L1/TNFR2 multi-gene humanized mice, in which blood cell composition, morphology and the levels of ALT, AST and other indicators were similar to the wild-type counterpart. Basal leukocyte subpopulations including T/B/NK cells, DC, granulocytes, and monocytes/macrophages, were similar between humanized and wild-type mice. Moreover, using the MC38 tumor model, the combination of anti-TNFR2 antibody and anti-PD-1 (or anti-PD-L1) shows enhanced effect compared to the individual groups, demonstrating that the PD-1/PD-L1/TNFR2 humanized mice have a potential to provide a powerful preclinical model for in vivo evaluation of combination therapies. In conclusion, TNFR2 and PD-1/PD-L1/TNFR2 humanized mice are a useful tool to explore anti-PD-1, anti-PD-L1 and anti-TNFR2 combination therapy strategies with promising activity and low cytotoxicity. Citation Format: Huilin Li, Xiaofei Zhou, Jing Zhang, Veronika Chromiko