title: Efficacy of systemic morpholino exon-skipping in Duchenne dystrophy dogs.
abstract: OBJECTIVE
  Duchenne muscular dystrophy (DMD) is caused by the inability to produce dystrophin protein at the myofiber membrane. A method to rescue dystrophin production by antisense oligonucleotides, termed exon-skipping, has been reported for the mdx mouse and in four DMD patients by local intramuscular injection. We sought to test efficacy and toxicity of intravenous oligonucleotide (morpholino)-induced exon skipping in the DMD dog model.
  
  
  METHODS
  We tested a series of antisense drugs singly and as cocktails, both in primary cell culture, and two in vivo delivery methods (intramuscular injection and systemic intravenous injection). The efficiency and efficacy of multiexon skipping (exons 6-9) were tested at the messenger RNA, protein, histological, and clinical levels.
  
  
  RESULTS
  Weekly or biweekly systemic intravenous injections with a three-morpholino cocktail over the course of 5 to 22 weeks induced therapeutic levels of dystrophin expression throughout the body, with an average of about 26% normal levels. This was accompanied by reduced inflammatory signals examined by magnetic resonance imaging and histology, improved or stabilized timed running tests, and clinical symptoms. Blood tests indicated no evidence of toxicity.
  
  
  CONCLUSIONS
  This is the first report of widespread rescue of dystrophin expression to therapeutic levels in the dog model of DMD. This study also provides a proof of concept for systemic multiexon-skipping therapy. Use of cocktails of morpholino, as shown here, allows broader application of this approach to a greater proportion of DMD patients (90%) and also offers the prospect of selecting deletions that optimize the functionality of the dystrophin protein.
authors.affiliation: Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC 20010, USA.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Yokota
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Lu
authors.forename: Terence
authors.initials: T
authors.lastname: Partridge
authors.forename: Masanori
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Akinori
authors.initials: A
authors.lastname: Nakamura
authors.forename: Shińichi
authors.initials: S
authors.lastname: Takeda
authors.forename: Eric
authors.initials: E
authors.lastname: Hoffman
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D005091:Exons / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D009025:Morpholines / Q000008:administration & dosage; D020388:Muscular Dystrophy, Duchenne / Q000235:genetics* / Q000628:therapy*; D032386:Myoblasts, Cardiac / Q000473:pathology; D017354:Point Mutation
chemical_list: D009025:Morpholines