DMD and Duchenne muscular dystrophy: Early systemic AAV delivery studies revealed the ability to deliver microdystrophin gene constructs to all striated muscles in a dose-dependent manner.36,54 Lower doses led to dystrophin expression in a mosaic pattern, which partially improved histology and strength, whereas higher doses led to more uniform levels of dystrophin and a more complete rescue of the dystrophic phenotype in mice.36,55 Phenotypic reversal was also observed in old mdx mice (up to 2 years old).30,56–58 Microdystrophin has been similarly effective in canine DMD models.35,38,59–62