"For example, we have observed continued exon skipping in the dystrophin transcript up to 14 weeks after a single intramuscular injection of a morpholino antisense molecule with concomitant expression of a modified dystrophin in the treated muscle of the dystrophic mdx mouse (Wells et al., unpublished)."

From: Wells DJ. Gene doping: the hype and the reality. Br J Pharmacol. 2008 Jun;154(3):623-31. Epub 2008 Apr 21.