title: Exon skipping and dystrophin restoration in patients with Duchenne muscular dystrophy after systemic phosphorodiamidate morpholino oligomer treatment: an open-label, phase 2, dose-escalation study.
abstract: BACKGROUND
  We report clinical safety and biochemical efficacy from a dose-ranging study of intravenously administered AVI-4658 phosphorodiamidate morpholino oligomer (PMO) in patients with Duchenne muscular dystrophy.
  
  
  METHODS
  We undertook an open-label, phase 2, dose-escalation study (0·5, 1·0, 2·0, 4·0, 10·0, and 20·0 mg/kg bodyweight) in ambulant patients with Duchenne muscular dystrophy aged 5-15 years with amenable deletions in DMD. Participants had a muscle biopsy before starting treatment and after 12 weekly intravenous infusions of AVI-4658. The primary study objective was to assess safety and tolerability of AVI-4658. The secondary objectives were pharmacokinetic properties and the ability of AVI-4658 to induce exon 51 skipping and dystrophin restoration by RT-PCR, immunohistochemistry, and immunoblotting. The study is registered, number NCT00844597.
  
  
  RESULTS
  19 patients took part in the study. AVI-4658 was well tolerated with no drug-related serious adverse events. AVI-4658 induced exon 51 skipping in all cohorts and new dystrophin protein expression in a significant dose-dependent (p=0·0203), but variable, manner in boys from cohort 3 (dose 2 mg/kg) onwards. Seven patients responded to treatment, in whom mean dystrophin fluorescence intensity increased from 8·9% (95% CI 7·1-10·6) to 16·4% (10·8-22·0) of normal control after treatment (p=0·0287). The three patients with the greatest responses to treatment had 21%, 15%, and 55% dystrophin-positive fibres after treatment and these findings were confirmed with western blot, which showed an increase after treatment of protein levels from 2% to 18%, from 0·9% to 17%, and from 0% to 7·7% of normal muscle, respectively. The dystrophin-associated proteins α-sarcoglycan and neuronal nitric oxide synthase were also restored at the sarcolemma. Analysis of the inflammatory infiltrate indicated a reduction of cytotoxic T cells in the post-treatment muscle biopsies in the two high-dose cohorts.
  
  
  CONCLUSIONS
  The safety and biochemical efficacy that we present show the potential of AVI-4658 to become a disease-modifying drug for Duchenne muscular dystrophy.
  
  
  BACKGROUND
  UK Medical Research Council; AVI BioPharma.
authors.affiliation: Dubowitz Neuromuscular Centre, UCL Institute of Child Health, London, UK.
authors.forename: Sebahattin
authors.initials: S
authors.lastname: Cirak
authors.forename: Virginia
authors.initials: V
authors.lastname: Arechavala-Gomeza
authors.forename: Michela
authors.initials: M
authors.lastname: Guglieri
authors.forename: Lucy
authors.initials: L
authors.lastname: Feng
authors.forename: Silvia
authors.initials: S
authors.lastname: Torelli
authors.forename: Karen
authors.initials: K
authors.lastname: Anthony
authors.forename: Stephen
authors.initials: S
authors.lastname: Abbs
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Garralda
authors.forename: John
authors.initials: J
authors.lastname: Bourke
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Wells
authors.forename: George
authors.initials: G
authors.lastname: Dickson
authors.forename: Matthew J A
authors.initials: MJ
authors.lastname: Wood
authors.forename: Steve D
authors.initials: SD
authors.lastname: Wilton
authors.forename: Volker
authors.initials: V
authors.lastname: Straub
authors.forename: Ryszard
authors.initials: R
authors.lastname: Kole
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Shrewsbury
authors.forename: Caroline
authors.initials: C
authors.lastname: Sewry
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Morgan
authors.forename: Kate
authors.initials: K
authors.lastname: Bushby
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
mesh_terms: D000293:Adolescent; D017398:Alternative Splicing; D002648:Child; D004305:Dose-Response Relationship, Drug; D016189:Dystrophin / Q000235:genetics / Q000378:metabolism*; D005091:Exons / Q000235:genetics*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D009025:Morpholines / Q000008:administration & dosage* / Q000493:pharmacokinetics; D060172:Morpholinos; D018482:Muscle, Skeletal / Q000378:metabolism; D020388:Muscular Dystrophy, Duchenne / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D009841:Oligonucleotides / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D016189:Dystrophin; D009025:Morpholines; D060172:Morpholinos; D009841:Oligonucleotides; C000611335:eteplirsen