The Dynamics of Compound, Transcript, and Protein Effects After Treatment With 2OMePS Antisense Oligonucleotides in mdx Mice

Antisense-mediated exon skipping is currently in clinical development for Duchenne muscular dystrophy (DMD) to amend the consequences of the underlying genetic defect and restore dystrophin expression. Due to turnover of compound, transcript, and protein, chronic treatment with effector molecules (antisense oligonucleotides) will be required. To investigate the dynamics and persistence of antisense 2'-O-methyl phosphorothioate oligonucleotides, exon skipping, and dystrophin expression after dosing was concluded, mdx mice were treated subcutaneously for 8 weeks with 100 mg/kg oligonucleotides twice weekly. Thereafter, mice were sacrificed at different time points after the final injection (36 hours-24 weeks). Oligonucleotide half-life was longer in heart (similar to 65 days) compared with that in skeletal muscle, liver, and kidney (similar to 35 days). Exon skipping half-lives varied between 33 and 53 days, whereas dystrophin protein showed a long half-life (> 100 days). Oligonucleotide and exon-skipping levels peaked in the first week and declined thereafter. By contrast, dystrophin expression peaked after 3-8 weeks and then slowly declined, remaining detectable after 24 weeks. Concordance between levels of oligonucleotides, exon skipping, and proteins was observed, except in heart, wherein high oligonucleotide levels but low exon skipping and dystrophin expression were seen. Overall, these results enhance our understanding of the pharmacokinetics and pharmacodynamics of 2'-O-methyl phosphorothioate oligos used for the treatment of DMD.