499. Intravenous Delivery of a Novel Micro-Dystrophin Vector Prevented Muscle Deterioration in Young Adult Canine Duchenne Muscular Dystrophy Dogs

Abstract

Duchenne muscular dystrophy (DMD) is a progressive, muscle wasting disorder that affects all muscles in the body. An effective gene therapy for DMD will require efficient whole body muscle transduction. It was recently demonstrated that a single intravenous injection of adeno-associated virus (AAV) can lead to safe, bodywide muscle gene transfer in adolescent dogs affected by the canine model of DMD (cDMD) (Yue et al. 2015 Hum Mol Genet). Here we evaluated systemic gene therapy in three 3.5-m-old cDMD dogs using a novel canine codon-optimized micro-dystrophin vector. Transcriptional regulation is controlled by the muscle-specific CK8 promoter and a synthetic polyadenylation signal. All experimental subjects received transient immune suppression. One dog was administrated with 5×1013 viral genome (vg) particles/kg of the vector. Two dogs received 1×1014 vg particles/kg of the vector. All dogs tolerated injection well. Blood biochemistry (weekly in the first four weeks and biweekly thereafter) was unremarkable. Growth curve was nominally disturbed during the immunosuppression regimen, but recovered thereafter. Biopsy at 1,3 and 6 months after injection revealed widespread micro-dystrophin expression in 50-80% myofibers. The dystrophin-associated glycoprotein complex, including neuronal nitric oxide synthase (nNOS), was restored. While limited in sample size, muscle damage usually seen in young adult untreated dogs (inflammation, fibrosis, calcification) were rarely observed. CD4+, CD8+, and regulatory T cells were minimally detected. Night activity monitoring showed a trend of improvement. Limb muscle force (both forelimb and hind limb) was significantly enhanced compared to that of pre-injection. Our data suggest that systemic AAV micro-dystrophin therapy may translate to large mammals afflicted by DMD (Supported by Solid GT, NIH, DOD, Jesse's Journey).