%0 Journal Article
%T Chemical modification of PS-ASO therapeutics reduces cellular protein-binding and improves the therapeutic index
%J -
%D 2019
%R https://doi.org/10.1038/s41587-019-0106-2
%X The molecular mechanisms of toxicity of chemically modified phosphorothioate antisense oligonucleotides (PS-ASOs) are not fully understood. Here, we report that toxic gapmer PS-ASOs containing modifications such as constrained ethyl (cEt), locked nucleic acid (LNA) and 2¡ä-O-methoxyethyl (2¡ä-MOE) bind many cellular proteins with high avidity, altering their function, localization and stability. We show that RNase H1¨Cdependent delocalization of paraspeckle proteins to nucleoli is an early event in PS-ASO toxicity, followed by nucleolar stress, p53 activation and apoptotic cell death. Introduction of a single 2¡ä-O-methyl (2¡ä-OMe) modification at gap position 2 reduced protein-binding, substantially decreasing hepatotoxicity and improving the therapeutic index with minimal impairment of antisense activity. We validated the ability of this modification to generally mitigate PS-ASO toxicity with more than 300 sequences. Our findings will guide the design of PS-ASOs with optimal therapeutic profiles
%U https://www.nature.com/articles/s41587-019-0106-2