The NSAA is a healthcare provider administered scale that rates performance of various motor abilities in ambulant children with Duchenne Muscular Dystrophy and is used to monitor disease progression and treatment effects. During assessment, participants are asked to perform 17 different functional activities that are graded as: 2 - "Normal" - no obvious modification of activity; 1 - Modified method but achieves goal independent of assistance; 0 - Unable to achieve independently. The NSAA total score is defined as the sum of all 17 items, ranging from 0 (worst) to 34 (best). The response vector consists of the change from baseline in NSAA total score at the post-baseline visit. The model includes the covariates of treatment group, visit, treatment group by visit interaction, age group, baseline NSAA total score, and baseline NSAA total score by visit interaction. All covariates are fixed effects in this analysis. An increase in score indicates an improvement in motor function.

An AE is any untoward medical occurrence in a clinical study participant that does not necessarily have a causal relationship with the study drug. An AE can, therefore, be any unfavorable and unintended symptom, sign, disease, condition, or test abnormality that occurs during or after administration of a study drug, whether or not considered related to the study drug. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.