A TEAE is any untoward medical occurrence or undesirable event(s) experienced in a participant that begins or worsens following administration of the study drug or study treatment, whether or not considered related to the treatment by the Investigator. A serious adverse event (SAE) was an adverse event (AE) resulting in any of the following outcomes or deemed significant for any other reason, death, initial or prolonged inpatient hospitalization, life-threatening experience (immediate risk of dying), or persistent or significant disability/incapacity not related to nmDBMD. AEs included both SAEs and non-serious AEs. AEs were classified according to National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0 (CTCAE) and coded using the Medical Dictionary for Regulatory Activities (MedDRA). A summary of serious and all other non-serious adverse events, regardless of causality, is located in the Reported Adverse Events module.

All enrolled participants who received at least 1 dose of study drug.

The 6MWD was assessed in participants who were ambulatory using standardized procedures. Participants were not permitted to use assistive devices (walker, long leg braces, or short leg braces) during the 6MWD test.

All enrolled participants who received at least 1 dose of study drug, were ambulatory, and had evaluable 6MWT data. Participants who were ambulatory were able to run/walk 10 meters in ≤30 seconds at study entry.

The NSAA was used to evaluate physical function in participants who were ambulatory at study entry, using standardized procedures. The NSAA consisted of 17 activities, each scored as 0 (activity could not be performed), 1 (modified method but achieved goal without physical assistance from another), or 2 (normal, achieved goal without assistance). The sum of these 17 scores was used to form a total score. If fewer than 13 of the 17 activities were performed, the total score was considered missing. If 13 to 16 activities were performed, the total score was calculated by multiplying the sum of the scores in the x activities that were performed by 17/x. If an activity could not be performed due to disease progression/loss of ambulation, a score of 0 was assigned. The linear score was the linear transformation of the NSAA score to a scale of 0 (worst) to 100 (best).

All enrolled participants who received at least 1 dose of study drug, were ambulatory, and had evaluable NSAA data. Participants who were ambulatory were able to run/walk 10 meters in ≤30 seconds at study entry.

Time to stand from the supine position to a standing position was assessed in ambulatory participants. If the time taken to perform a test exceeded 30 seconds or if a participant could not perform the test due to disease progression, a value of 30 seconds was used.

All enrolled participants who received at least 1 dose of study drug, were ambulatory, and had evaluable time to stand from supine data. Participants who were ambulatory were able to run/walk 10 meters in ≤30 seconds at study entry.

Time to walk/run 10 meters was measured in ambulatory participants. If the time taken to perform a test exceeded 30 seconds or if a participant could not perform the test due to disease progression, a value of 30 seconds was used.

All enrolled participants who received at least 1 dose of study drug, were ambulatory, and had evaluable data for time to walk/run 10 meters. Participants who were ambulatory were able to run/walk 10 meters in ≤30 seconds at study entry.

Pulmonary function parameters of %-predicated FVC, percent-predicted FEV1 (adjusted using ulna length and age), PEF, and PCF was assessed in non-ambulatory participants by using a spirometer. Due to the difficulty in obtaining an accurate standing height measurement in non-ambulatory participants, ulna length and arm span were used as a surrogate measure for height when calculating percent-predicted FVC.

All enrolled participants who received at least 1 dose of study drug, were non-ambulatory, and had evaluable spirometry data. Participants who were non-ambulatory were not able to run/walk 10 meters in ≤30 seconds at study entry.

Activities of daily living after loss of ambulation were measured using the EK scale. The EK scale is an ordinal scale ranging from 0 to 30 points where 0 represents the highest level of independent function and 30 the lowest. The scale consists of 10 categories (each scored 0 to 3), involving different functional domains including 1) ability to use wheelchair, 2) ability to transfer from wheelchair, 3) ability to stand, 4) ability to balance in the wheelchair, 5) ability to move arms, 6) ability to use hands and arms when eating, 7) ability to turn in bed, 8) ability to cough, 9) ability to speak, and 10) physical well-being. The administration of the EK scale consisted of an interview of the participant to capture how he performs the tasks of daily life (as described by Categories 1 to 9) and how he perceives his wellbeing (as described by Category 10). The interviewer observed the participant and assigned the final score for the tasks that could be observed in the clinic.

All enrolled participants who received at least 1 dose of study drug, were non-ambulatory, and had evaluable EK scale data. Participants who were non-ambulatory were not able to run/walk 10 meters in ≤30 seconds at study entry.