Dystrophin results from a pre-specified analysis of ambulatory boys showed: Mean absolute muscle content-adjusted dystrophin expression was 9.0% (range: 4.6-13.9%) and mean absolute unadjusted dystrophin expression was 5.5% of normal (range: 3.3-8.3%), as measured by Western Blot. [...] 89% of ambulatory participants achieved muscle content-adjusted dystrophin levels of at least 5%.