Abstract 563: A biparatopic agonist antibody for OX40 that exhibits superior activity without secondary crosslinking

Abstract

Abstract The development of agonistic antibodies that activate T-cell co-stimulatory pathways represents a therapeutic strategy with significant clinical potential. However, challenges remain for the translation from in vitro efficacy to clinical success. OX40 and other tumor necrosis factor receptor (TNFR) superfamily members are notorious for requiring high-order receptor clustering in order to achieve full activity. For monoclonal antibodies, this high-order clustering is generally achieved through secondary cross-linking strategies. In vivo, this secondary cross-linking is often supplied through internal immune effector cells via Fc engagement. Bispecific and biparatopic antibodies represent an emerging class of drug molecules that enable unique mechanisms of action relative to their monoclonal counterparts. Here, we describe the use of our bispecific platform for the generation of large panels of biparatopic antibodies which enabled high-throughput screening for the discovery of an array of OX40 agonistic molecules. We have optimized these multivalent antibodies that exceed the potency of the OX40 ligand in NFkB activation without the need for secondary cross-linking. These agonist antibodies have additionally been characterized using primary T cell assays to monitor the kinetics of growth proliferation and cytokine secretion, outperforming cross-linked antibodies currently being tested in clinical trials. In co-culture systems, these agonist antibodies were effective in inhibiting immuno-suppressive properties of Tregs. Our lead OX40 agonist antibody has been optimized for activity and developability and has entered stable cell line development to further support pre-clinical activities. Citation Format: Bonnie Hammer, Mandar Bawadekar, Matthew Bissen, John Painter, Lauren Lehmann, Francis Qufei Li, Lucas Bailey, Bryan Glaser, Roland Green. A biparatopic agonist antibody for OX40 that exhibits superior activity without secondary crosslinking [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 563.