Abstract 1076: Hexavalent HERA-CD40L induces a productive T cell-mediated anti-tumor immune response and shows superior activity in comparison to benchmark CD40 agonistic antibodies
Authors: Gieffers Christian , Richards David M. , Sykora Jaromir , Merz Christian , Sefrin Julian P. , Billian-Frey Katharina , Heinonen Karl , Müller Mauricio Redondo , Schröder Matthias , Thiemann Meinolf , Hill Oliver 
Published: September 2020

Abstract
TNF Receptor Superfamily members (TNF-R-SF), including CD40, are key regulators of the immune system and have been immunotherapeutic targets for over 20 years. CD40 signaling serves as an important co-stimulatory signal for antigen-presenting cells (APC). For the induction of a CD40 driven anti-tumor immune response multiple approaches, - most of them antibody based - are currently under investigation. However, the structural necessity of trimerization within the TNF-R-SF, defines bivalent antibodies generally as unfeasible inducers of signaling events within this protein family. To overcome the known inadequacies of antibodies, we developed HERA-CD40L, composed of two trivalent CD40L-receptor-binding domains, fused to a silenced human IgG1 Fc-domain. This hexavalent CD40 agonist mimics the natural ligand and enables efficient receptor clustering and superior signaling. HERA-CD40L treatment increased the pro-inflammatory state of all CD40-expressing cells examined. It promoted the licensing of dendritic cells (DC), macrophages, B cells and other APC. Comparison to benchmark antibodies revealed that HERA-CD40L elicited a stronger and more rapid activation of NFκB signaling in primary B cells. HERA-CD40L treatment, but not clinical benchmark antibodies triggered immediate NFκB, MAPK, PI3K and STAT-1 signaling in primary monocyte-derived immature DC. As a result, HERA-CD40L induced upregulation of activation markers and co-stimulatory molecules in B cells and DC. Using SEC fractionation followed by a CD40 reporter assay, we could furthermore demonstrate that the activity of a clinical benchmark antibody derived exclusively from antibody aggregates. In vitro HERA-CD40L treatment converted immature phagocytic macrophages into mature/professional APC and induced repolarization of M2- to M1-like macrophages. These findings were confirmed in vivo using a mouse surrogate (mmHERA-CD40L). Upon treatment of MC38-CEA and CT26wt syngeneic mouse models, we observed single agent anti-tumor efficacy. In the CT26wt model, mmHERA-CD40L treatment converted cold into hot tumors by increasing T cell infiltration. Furthermore, mmHERA-CD40L induced a strong dose dependent decrease of tumor associated pro-tumorigenic M2-macrophages indicating a profound reorganization of the tumor microenvironment. Both in vitro (human) and in vivo (mouse), HERA-CD40L increased antigen-specific immune system activation without affecting the non-specific immune cells. These data, together with pilot PD/safety results, demonstrate that the activity of HERA-CD40L is both potent and safe. In conclusion, HERA-CD40L is a potent agonist able to show single agent anti-tumor activity. The biological activity is distinct from and superior to clinical benchmark “agonistic” antibodies. HERA-CD40L has a well-defined mechanism of action, does not depend on Fc gamma receptor-mediated crosslinking and hence functions as a true agonist.
Citation Format: Christian Gieffers, David M. Richards, Jaromir Sykora, Christian Merz, Julian P. Sefrin, Katharina Billian-Frey, Karl Heinonen, Mauricio Redondo Müller, Matthias Schröder, Meinolf Thiemann, Oliver Hill. Hexavalent HERA-CD40L induces a productive T cell-mediated anti-tumor immune response and shows superior activity in comparison to benchmark CD40 agonistic antibodies [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 1076.