Abstract 3261: EOS100850, a non-brain penetrant highly selective A2Areceptor antagonist, uniquely maintains high potency within the adenosine rich tumor microenvironment
Authors: Houthuys Erica , Basilico Paola , Brouwer Margreet , Deregnaucourt Theo , Detheux Michel , Driessens Gregory , Gomes Bruno , Leroy Xavier , Marchante Joao , Marillier Reece , Swiercz Jakub , Crosignani Stefano 
Published: August 2019

Abstract
High levels of extracellular adenosine in the tumor microenvironment promote tumor immune evasion. We and others have shown that adenosine, predominantly through the A2A receptor, suppresses innate and adaptive immune cell responses leading to suppression of antitumor immunity. We demonstrated that A2A receptor antagonists initially designed for Parkinson’s disease but repurposed for immuno-oncology dramatically loose potency in a high adenosine environment. We therefore developed EOS100850, an A2A receptor antagonist specifically designed as a potent, highly selective, non-brain penetrant orally administered agent to treat a wide range of tumor types. EOS100850 has been discovered via structure-based drug design followed by rational medicinal chemistry to improve drug-like properties. EOS100850 demonstrated nanomolar affinity and high selectivity for human A2A receptors, with pico- to nanomolar potency on human and mouse A2A receptors. Assays were performed on A2A-overexpressing HEK293 cells and primary human T cells, using conditions mimicking normal physiological and tumor-like microenvironments. In these assays, EOS100850 potency was not affected by increasing extracellular adenosine concentrations. A unique feature of this compound is the remarkable long residence time on human A2A receptors after binding, resulting in a prolonged inhibition of A2A receptor signaling at a wide range of adenosine concentrations (up to 1000 µM). Furthermore, unlike competitor A2A receptor antagonists, EOS100850 reversed with nanomolar potency A2A receptor-dependent inhibition of cytokine secretion by T cells in tumor-like assay conditions. EOS100850 potency to inhibit A2A receptor-mediated CREB phosphorylation in T cells in human and mouse whole blood was in the low nanomolar range.One of the major metabolites of EOS100850, EOS100612, identified both in vitro and in vivo, has been synthesized and was found to be active on A2A receptors. Similar to EOS100850, EOS100612 displayed pico- to nanomolar potency, high selectivity and long residence time on A2A receptors in various in vitro assays.In conclusion, EOS100850 represents a novel non-brain penetrant best-in-class A2A receptor antagonist. It remains highly potent in environments characterized by high adenosine concentrations, such as the TME, maximizing the potential intra-tumor effect and further minimizing the risk of collateral CNS toxicity.
Citation Format: Erica Houthuys, Paola Basilico, Margreet Brouwer, Theo Deregnaucourt, Michel Detheux, Gregory Driessens, Bruno Gomes, Xavier Leroy, Joao Marchante, Reece Marillier, Jakub Swiercz, Stefano Crosignani. EOS100850, a non-brain penetrant highly selective A2Areceptor antagonist, uniquely maintains high potency within the adenosine rich tumor microenvironment [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 3261.