Locked nucleic acid-modified antisense oligonucleotides for enhanced exon skipping in Duchenne muscular dystrophy

Abstract

Oligonucleotides have gained significant interest in recent years towards the development of therapeutics and diagnostics against several diseases. The first such drug to enter the clinic has been Vitravene, used for the treatment of cytomegaloviral retinitis. Later, Macugen was approved for the treatment of macular degeneration, and very recently Kynamro against familial hypercholesterolemia. Oligonucleotides composed natural nucleotide monomers pose severe limitations, including poor nuclease resistance and decreased target binding affinity, and are not suitable for therapeutic developments. To overcome these challenges, chemically‐modified nucleic acid analogues are used. One of the most prominent and successful analogues is locked nucleic acid (LNA) [1,2]. We are developing LNA and other chemically‐modified therapeutic oligonucleotides to improve the efficacy and pharmacokinetic properties. Very recently, we have investigated the potential of LNA‐modified antisense oligonucleotides (LNA AOs) for exon skipping in Duchenne muscular dystrophy (DMD) [3]. LNA AOs were designed in combination with 2'‐OMe‐modified RNA nucleotides (20mer and a truncated 18mer LNA/OMe AOs) for targeting exon 23 of the dystrophin gene in mouse (mdx mouse with exon 23 point mutation) primary myoblast cells. A fully‐modified 20mer 2'OMe AOs were also used for comparison. The results showed that LNA‐modified AOs are highly efficient in exon 23 skipping. Notably, the truncated 18mer LNA/OMe AO also induced efficient skipping of exon 23. These preliminary results clearly indicate that the development of highly potent LNA AOs in combination with various other chemistries could substantially improve the accuracy and efficiency of exon skipping