Altered Biodistribution and Hepatic Safety Profile of a Gapmer Antisense Oligonucleotide Bearing Guanidine-Bridged Nucleic Acids.

Guanidine-bridged nucleic acid (GuNA) is a novel 2',4'-bridged nucleic acid/locked nucleic acid (2',4'-BNA/LNA) analog containing cations that exhibit strong affinity for target RNA and superior nuclease resistance. In this study, Malat1 antisense oligonucleotide (ASO) bearing GuNA was evaluated for target knockdown (KD) activity and tolerability. The GuNA ASO did not interfere with RNase H recruitment on the target RNA/ASO heteroduplex and did show potent target KD activity in a skeletal muscle-derived cell line equivalent to that of the LNA ASO under gymnotic conditions, whereas almost no KD activity was observed in a hepatocyte-derived cell line. The GuNA ASO exhibited potent KD activity in various tissues; the KD activity in the skeletal muscle was equivalent with that of the LNA ASO, but the KD activities in the liver and kidney were clearly lower compared with the LNA ASO. In addition, despite the higher accumulation of the GuNA ASO in the liver, levels of aspartate aminotransferase and alanine aminotransferase with the GuNA ASO administration were not elevated compared with those induced by the LNA ASO. Our data indicate that the GuNA ASO is tolerable and exhibits unique altered pharmacological activities in comparison with the LNA ASO in terms of the relative effect between liver and skeletal muscle.