In vitro and in vivo models to predict ADAR RNA editing oligonucleotides potential in human liver tissue
Liver-originated diseases remain a significant global health burden, with limited treatment options available. RNA therapeutics, particularly adenosine deaminase acting on RNA (ADAR)-mediated  editing using editing oligonucleotides (EONs) offer a novel approach to address these unmet medical needs. This study evaluates in vitro and in vivo liver models to predict the therapeutic potential of chemically modified EONs in human liver tissue, using ACTB as target. Multiple liver models, including primary human hepatocytes (PHH), cancer-derived cell lines, and iPSC-derived hepatocytes in both 2D and 3D formats, were characterized for ADAR expression, liver functionality, and RNA editing efficiency. The results show consistent ADAR expression across most models, with 3D models, particularly PHH spheroids and liver microtissues, closely mimicking human liver tissue in gene expression and editing capacity. In vivo, non-human primate liver biopsies showed high levels of ACTB editing, consistent with findings from PHH models. These findings highlight the critical role of preclinical models in EON selection, where multiple factors must be carefully considered. A multimodel assessment utilizing composite scoring to comprehensively assess the key parameters seems to be the approach of choice to maximize translatability across preclinical models and increase the likelihood of success in clinical applications.