Abstract 2136: ADORA2A specific antibodies show enhancement of anti-tumour immunity

Background: ADORA2A (A2AR), is an adenosine receptor that suppresses immune cell toxicity through sensing extracellular adenosine. A2AR belongs to a group of seven-transmembrane receptor proteins called G protein-coupled receptors (GPCRs) which act as detectors to various signals from outside the cell. We aim to reduce the immunosuppressive properties of adenosine in the tumor microenvironment (TME) by targeting A2AR with monoclonal antibodies (mAbs). mAbs are an attractive modality to therapeutically target complex multi-pass membrane proteins, but mAb development is hindered by many challenges. Here we report the discovery and functional characterization of 23 A2AR-specific monoclonal antibodies developed using Icosagen’s proprietary antigen displaying Virus-Like-Particle (VLP) based chicken immunization and mAb screening platforms. Methods: Monoclonal antibodies against A2AR were generated using a DNA or mRNA and VLP-based immunization strategy. VLPs were generated using a proprietary technology ensuring high density of display of A2AR on VLPs. Chickens were selected as immunization hosts due to being evolutionally more divergent from mammals increasing the chance of immunogenicity and obtaining antibody candidates against conserved membrane proteins. Antibody discovery was performed with Icosagen’s proprietary HybriFree B-cell cloning technology, complemented with chicken derived phage display library screening platform. Antibody specificity was confirmed using VLP-based immunoassays and overexpression cell lines. Antagonistic function of A2AR-specific antibodies was confirmed on immune cells and reporter cell line-based assays. Results: Immunization of chicken and dynamic antibody discovery methods resulted in discovery of 23 unique A2AR-specific antibody clones. These antibodies exhibit high affinity binding to A2AR, as indicated by low nanomolar EC50 values determined through cell-based assays, complemented with SPR analysis using A2AR-expressing nanoparticles. Antibody clones with A2AR-antagonistic function show enhancement of T cell activation upon A2AR agonist treatment, highlighting their potential to boost anti-tumor immune response. These antibodies can further translate into boosting CAR-T efficacy in overcoming suppressive TME, thereby expanding it for treatment for solid tumors. Conclusions: This study presents highly specific monoclonal antibodies targeting the adenosine receptor ADORA2A. The lead antibody clones exhibiting antagonistic function in vitro will undergo further optimization using Icosagen's phage display-based affinity maturation platform. This process aims to enhance their properties for development into clinical candidates, advancing therapeutic interventions targeting ADORA2A and supporting their potential in immunotherapy applications. Citation Format: Paule Hermet, Siret Tahk, Gaily Kivi, Joan Teyra, Madis Jakobson, Ana Shahpazir, Liis Siigur, Robin Löving, Reet Kurg, Mart Ustav, Andres Männik, Mart Ustav. ADORA2A specific antibodies show enhancement of anti-tumour immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2136.