Abstract 936: Targeting TNFR2 for cancer immunotherapy: Ligand blocking depletors versus receptor agonists
Authors: Mårtensson Linda , Cleary Kirstie , Semmrich Monika , Kovacek Mathilda , Holmkvist Petra , Svensson Caroline , Demiri Mimoza , Blidberg Therese , Thornberg Ulla-Carin , Pitic Vincentiu , Dadas Osman , Lim Sean H. , Beers Stephen A. , Cragg Mark S. , Frendéus Björn , Teige Ingrid 
Published: September 2020

Abstract
The pleiotropic TNF-α:TNFR axis plays a central role in the immune system. While the cellular expression of TNFR1 is broad, TNFR2 expression is mainly restricted to immune cells and especially high on T regs. The therapeutic potential of targeting TNFR2 for cancer treatment has been previously indicated but the mechanism-of-action (MoA) of these reagents remains unclear, with conflicting data reported by different investigators. To gain further insight, we identified and characterized a wide panel of human and mouse TNFR2-specific antibodies, generated from the n-CoDeR F.I.R.S.T™ phage display platform. Based on their ability to block TNF-α:TNFR2 binding and to agonize or antagonize TNFR2 signaling, we identified parallel human and mouse TNFR2-specific antibodies with activities ranging from agonist to antagonist, and from complete ligand blocking to non-blocking. Two antibody variants with distinctly opposing in vitro activities (complete ligand-blocking antagonist versus non-blocking agonist), were expressed in various IgG formats preferentially engaging activating FcγR (mIgG2a), inhibitory FcγR (mIgG1), or no FcγR (N297A Fc-mutated) and screened for in vivo antitumor activity. Both anti-TNFR2 antibody clones displayed anti-tumor efficacy but showed strikingly different FcγR-dependence for optimal antitumor activity. Further characterization demonstrated potent anti-tumor efficacy across several syngeneic in vivo cancer models (CT26, MC38 and B16), both as single agents, and when combined with anti-PD-1. In vivo mode-of-action studies indicated different initial events are evoked by the two antibodies but that they ultimately converge to elicit a similar immune modulation within the tumor that is associated with anti-tumor efficacy. The antagonist antibody caused early intra-tumoral T reg depletion, while the agonist caused dramatic CD8+ T cell increases. Over time, both antibodies induce an increase in effector T cells at the tumor site, improved CD8/T reg ratios, and tumor regression. In addition, the two antibodies similarly modulated the tumor myeloid content. Based on careful MoA-characterization, two human lead candidate anti-TNFR2 antibodies are being developed for treatment of solid cancer; BI-1808, a ligand-blocking T reg depleting antibody and BI-1910, a TNFR2 agonist.
Citation Format: Linda Mårtensson, Kirstie Cleary, Monika Semmrich, Mathilda Kovacek, Petra Holmkvist, Caroline Svensson, Mimoza Demiri, Therese Blidberg, Ulla-Carin Thornberg, Vincentiu Pitic, Osman Dadas, Sean H. Lim, Stephen A. Beers, Mark S. Cragg, Björn Frendéus, Ingrid Teige. Targeting TNFR2 for cancer immunotherapy: Ligand blocking depletors versus receptor agonists [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 936.