Employing RNA editing to engineer personalized tumor-specific neoantigens (editopes) Pecori, Riccardo Casati, Beatrice Merdler-Rabinowicz, Rona Landesman, Netanel Sanghvi, Khwab Zens, Stefan Kipfstuhl, Kai Pinamonti, Veronica Arnold, Annette Lindner, John M. Platten, Michael Offringa, Rienk Carretero Coca, Rafael Ruppin, Eytan Levanon, Erez Y. Papavasiliou, Fotini Nina neoantigen RNA editing ADAR1 Financiado por: Division of Immune Diversity, German Cancer Research Centre (DKFZ), Heidelberg, 69120, Germany. Cancer Data Science Lab, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, United States. Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel. Division of Neuroimmunology and Brain Tumor Immunology, German Cancer Research Centre (DKFZ), Heidelberg, 69120, Germany. Division of Molecular Oncology of Gastrointestinal Tumors, German Cancer Research Centre (DKFZ), Heidelberg, 69120, Germany. DKFZ Drug Discovery Lab (D3Lab), German Cancer Research Centre (DKFZ), Heidelberg, 69120, Germany. Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany. BioMed X Institute, 69120 Heidelberg, Germany. DKTK (German Cancer Consortium) Clinical Cooperation Unit (CCU) Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany. Department of Neurology, Medical Faculty Mannheim, MCTN, University of Heidelberg, Mannheim, Germany. German Cancer Consortium (DKTK), DKFZ, Core Center Heidelberg, Germany. Hertie Network of Excellence in Clinical Neuroscience. DKFZ-Hector Cancer Institute at University Medical Center Mannheim, Mannheim, Germany. Helmholtz Institute for Translational Oncology (HI-TRON) Mainz, German Cancer Research Center, Mainz, Germany. Department of Biochemistry, molecular Biology 3 and immunology. University of Granada, Spain. Increasing the quantity and immunogenicity of neoantigens in tumors is essential for advancing immunotherapy. However, engineering neoantigens remains challenging due to the need for precise, tumor-specific antigen modification without affecting normal cells. To tackle this challenge, we developed Short Precise-Encodable ADAR Recruiting (SPEAR) ADAR-engagers, an approach that uses short guide RNAs to engage the endogenous RNA editor ADAR1 and direct it to regions of mRNA targets known to encode MHC-presented peptides. By precisely editing adenosine-to-inosine (A-to-I) in these contexts, we effectively mutate specific epitopes into neoepitopes (which we now term “editopes”). As proof of concept, we targeted the known antigen MART-1 (Melanoma-Associated Antigen Recognized by T cells-1), and demonstrated that guided ADAR1 editing can generate immunogenic epitopes that activate T cells and promote tumor cell elimination. Building on this concept, we developed a computational pipeline to identify tumor-specific somatic mutations suitable for SPEAR-mediated editing. This strategy enables selective neoantigen generation in cancer cells, effectively increasing their apparent tumor mutational burden and potentially enhancing their susceptibility to immunotherapy. 2025-12-04T10:37:45Z 2025-12-04T10:37:45Z 2025-11-12 journal article Pecori, Riccardo et al. Employing RNA editing to engineer personalized tumor-specific neoantigens (editopes). bioRxiv preprint. https://doi.org/10.1101/2023.03.16.532918, this version posted November 12, 2025 https://hdl.handle.net/10481/108580 10.1101/2023.03.16.532918 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional bioRxiv preprint