RNA Reduction and Hepatotoxic Potential Caused by Non-Gapmer Antisense Oligonucleotides

Antisense oligonucleotides (ASOs) are classified into gapmer and non-gapmer types according to their chemical modification pattern and mechanism of action. Although gapmer ASOs effectively reduce target RNA expression through intracellular RNase H1, high-affinity gapmer ASOs also have hepatotoxic potential. Non-gapmer ASOs, which are mainly used for pre-mRNA splicing regulation or functional inhibition of microRNA through their steric effects, are also able to inhibit target RNA expression using nonsense-mediated decay. However, it was unknown if they induce high knockdown activity without showing hepatotoxicity. In this study, we investigated the modification pattern of non-gapmer ASOs and show that they have comparable knockdown potential if they have an appropriate melting temperature (T_m) range. We also demonstrated that non-gapmer ASOs show high knockdown effects without inducing hepatotoxicity in the mouse liver. These results indicated that non-gapmer ASOs have the potential to become an alternative inhibitor of target expression with a lower risk of hepatotoxicity.