Forelimb Treatment in a Large Cohort of Dystrophic Dogs Supports Delivery of a Recombinant AAV for Exon Skipping in Duchenne Patients
Le Guiner C., Montus M., Servais L., Cherel Y., Francois V., Thibaud JL., Wary C., Matot B., Larcher T., Guigand L., Dutilleul M., Domenger C., Allais M., Beuvin M., Moraux A., Le Duff J., Devaux M., Jaulin N., Guilbaud M., Latournerie V., Veron P., Boutin S., Leborgne C., Desgue D., Deschamps JY., Moullec S., Fromes Y., Vulin A., Smith RH., Laroudie N., Barnay-Toutain F., Rivière C., Bucher S., Le TH., Delaunay N., Gasmi M., Kotin RM., Bonne G., Adjali O., Masurier C., Hogrel JY., Carlier P., Moullier P., Voit T.
© The American Society of Gene & Cell Therapy. Duchenne muscular dystrophy (DMD) is a severe musclewasting disorder caused by mutations in the dystrophin gene, without curative treatment yet available. Our study provides, for the first time, the overall safety profile and therapeutic dose of a recombinant adeno-associated virus vector, serotype 8 (rAAV8) carrying a modified U7snRNA sequence promoting exon skipping to restore a functional in-frame dystrophin transcript, and injected by locoregional transvenous perfusion of the forelimb. Eighteen Golden Retriever Muscular Dystrophy (GRMD) dogs were exposed to increasing doses of GMP-manufactured vector. Treatment was well tolerated in all, and no acute nor delayed adverse effect, including systemic and immune toxicity was detected. There was a dose relationship for the amount of exon skipping with up to 80% of myofibers expressing dystrophin at the highest dose. Similarly, histological, nuclear magnetic resonance pathological indices and strength improvement responded in a dose-dependent manner. The systematic comparison of effects using different independent methods, allowed to define a minimum threshold of dystrophin expressing fibers (33% for structural measures and 40% for strength) under which there was no clear-cut therapeutic effect. Altogether, these results support the concept of a phase 1/2 trial of locoregional delivery into upper limbs of nonambulatory DMD patients.