6MWD measured the distance in meters a participant was able to walk in 6 minutes. The study used 6MWD procedure modified specifically for use in boys with Duchenne muscular dystrophy (DMD), including standardized verbal encouragement at specific intervals to maintain attention to the test, and use of a "safety chaser" to walk behind the participant during testing (McDonald et al., 2010a). The LS mean (LSM) change from baseline, standard error was derived using mixed model repeated measures (MMRM) methodology with factors for pooled country, treatment, visit, treatment-by-visit interaction and baseline 6MWD as a covariate.

All randomized participants who received at least one dose of study drug who had a baseline and at least one post-baseline measurement.

The NSAA is a functional scale specifically designed for ambulant boys with DMD that can provide additional information on motor functions important in maintaining normal ambulation and other activities important to everyday life. The NSAA is a 17-item evaluation of standing, ability to transition from lying to sitting, sitting to standing, and other mobility assessments. Each of the 17 items is evaluated on an ordinal scale of 0, 1, or 2, with higher scores reflecting better performance on the assessment, for a total maximum score of 34. This score was transformed to a 0 to 100 scale for the key analysis (referred to as linearized), with higher transformed scores reflecting better performance.The LS mean (LSM) change from baseline standard error was derived using mixed model repeated measures methodology (MMRM) with factors for pooled country, treatment, visit, treatment-by-visit interaction and Day 1 value as baseline covariate.

All randomized participants who received at least one dose of study drug who had a baseline and at least one post-baseline measurement.

Timed function tests included time it took to rise from floor, walk 10 meters, ascend 4 stairs, and descend 4 stairs.The lower the time in seconds taken, the better the performance. The LS mean change from baseline, standard error, was derived using mixed model repeated measures methodology (MMRM) with factors for pooled country, treatment, visit, treatment-by-visit interaction and Day 1 value as baseline covariate.

All randomized participants who received at least one dose of study drug who had a baseline and at least one post-baseline measurement.

Time on study until the 6MWD becomes 10% less than the baseline 6MWD and continues at that level or lower until the end of study.

All randomized participants who received at least one dose of study drug who had complete evaluable data. Complete evaluable data was defined as having baseline measurement, complete dates at evaluable visits and a post-baseline measurement at each evaluable visit. Censored participants: placebo=71, 0.3 mg/kg=63, 0.6 mg/kg=61.

Time on study until the TFT becomes 10% worse than the baseline TFT and continues at that level or lower until the end of study. The time to persistent 10% worsening is the observed time after baseline until the first observed timepoint where their time used for the TFTs is >110% of the baseline time and all the time values observed afterward are also >110% of baseline. If the participant discontinues prior to experiencing persistent worsening, this outcome for the participant is censored at the date of discontinuation of the double-blind period.

Only participants with complete evaluable data were analyzed. Complete evaluable data was defined as having baseline measurement, complete dates at evaluable visits and a post-baseline measurement at each evaluable visit.

All randomized participants who received at least 1 dose of study drug who had complete evaluable data.Censored participants:Rise from Floor;placebo(pl)=40,0.3 mg/kg=39,0.6 mg/kg=43;Stair Climb;pl=55,0.3 mg/kg=45,0.6 mg/kg=52;10 Meter Walk/Run pl=61,0.3 mg/kg=65,0.6 mg/kg=58,Stair Descend;pl=63,0.3 mg/kg=60,0.6 mg/kg=59.

PODCI includes a Global Functioning Scale and 5 core scales:Upper Extremity and Physical Function,Transfer/Basic Mobility, Sports/Physical Functioning, Pain/Comfort,and Happiness.The Global Functioning Scale is the mean of the mean scores from 4 of the 5 core scales (all except the happiness core scale).The following PODCI scores were prespecified in the protocol for analysis: Global Functioning, Upper Extremity and Physical Function,Transfer/Basic Mobility, and Sports/Physical Functioning. The Global Functioning Scale and each of the core scales were standardized so that a score of "0" represents a poor outcome/worse health, while "100" is the best possible outcome/best health (i.e., complete range of each score is 0 to 100, with higher scores representing better functioning). The LS mean (LSM) change from baseline,standard error was derived using MMRM with factors for pooled country, treatment, visit, treatment-by-visit interaction and baseline PODC scale as covariate.

All randomized participants who received at least one dose of study drug who had a baseline and at least one post-baseline measurement. The reason the number of participants analyzed is significantly less than the total number of randomized participants is because PODCI was administered only in English.

The data reported are population estimate and inter-patient variability.

All randomized participants who received at least one dose of study drug and had evaluable PK data.