The 6MWD test is a non-encouraged test performed in a 30 meters long flat corridor, where the participant is instructed to walk as far as possible, back and forth around two cones, with the permission to slow down, rest, or stop if needed. Ambulation was assessed via the 6MWD test following standardized procedures by measuring the 6MWD in meters. Participants were not permitted to use assistive devices (walker, long leg braces, or short leg braces) during the 6MWD test. Participants with confirmed loss of ambulation at a particular visit were assigned a 6MWD result of 0. Baseline and Week 48 6MWD values are each the average of two valid 6MWD values, or a single available value if one was missing.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Multiple imputation was applied to impute missing values within the treatment groups.

The 6MWD test is a non-encouraged test performed in a 30 meters long flat corridor, where the participant is instructed to walk as far as possible, back and forth around two cones, with the permission to slow down, rest, or stop if needed. Ambulation was assessed via the 6MWD test following standardized procedures by measuring the 6MWD in meters. Participants were not permitted to use assistive devices (walker, long leg braces, or short leg braces) during the 6MWD test. Time to 10% persistent worsening in 6MWD was defined as the last time that 6MWD was not 10% worse compared with baseline. Time to 10% persistent worsening in 6MWD <300 meters, >=300 to 400 meters, and >=400 meters was evaluated. For participants who did not have 10% 6MWD worsening or who were removed from study, time to 10% 6MWD worsening was censored at the time of the last 6MWD test. Participants who became non-ambulatory were considered to have 10% worsening.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Multiple imputation was applied to impute missing values within treatment groups. Here, 'Number analyzed 'signifies participants evaluable for specified categories.

During the test for walking/running 10 meters, the method of walk/run used by the participant was categorized as follows: 1. Unable to walk independently; 2. Unable to walk independently but can walk with support from a person or with assistive device (full leg calipers [knee-ankle-foot orthoses ] or walker); 3. Highly adapted gait, wide-based lordotic gait, cannot increase walking speed; 4. Moderately adapted gait, can pick up speed but cannot run; 5. Able to pick up speed but runs with a double stance phase (that is, cannot achieve both feet off the ground); 6. Runs and gets both feet off the ground (with no double stance phase). 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. A cumulative change from baseline data has been reported.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Overall number of participants analyzed' signifies participants evaluable for this outcome measure.

During the test for stair-climbing, the method of climbing used by the participant was categorized as follows: 1. Unable to up climb 4 standard stairs; 2. Climbs 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), using both arms on one or both handrails; 3. Climbs 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), using one arm on one handrail; 4. Climbs 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), not needing handrail; 5. Climbs 4 standard stairs alternating feet, needs handrail for support; 6. Climbs 4 standard stairs alternating feet, not needing handrail support. A cumulative change from baseline data has been reported.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Overall number of participants analyzed' signifies participants evaluable for this outcome measure.

During the test for stair-descending, the method of descending used by the participant was categorized as follows: 1. Unable to descend 4 standard stairs; 2. Descends 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), using both arms on one or both handrails; 3. Descends 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), using one arm on one handrail; 4. Descends 4 standard stairs "marking time" (climbs one foot at a time, with both feet on a step before moving to next step), not needing handrail; 5. Descends 4 standard stairs alternating feet, needs handrail for support; 6. Descends 4 standard stairs alternating feet, not needing handrail support. A cumulative change from baseline data has been reported.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Overall number of participants analyzed' signifies participants evaluable for this outcome measure.

Physical function was assessed via the NSAA, a functional scale specifically designed for ambulant Duchenne muscular dystrophy (DMD) participants. The assessment comprised tests for 17 abilities of a participant, such as ability to stand, rise from the floor, get from lying to sitting, get from sitting to standing, raise one's head, stand on one's heels, hop, jump, and run. For each activity, a score of 0, 1, or 2 was recorded, with 0 = "unable to achieve independently," 1 = "modified method but achieves goal independent of physical assistance from another," or 2 = "normal- achieves goal without any assistance." The sum of these scores (except for 'raise one's head' activity score) was reported as the ordinal total score, which was transformed to a linear total score ranging from 0 (worst) to 100 (best). Participants with confirmed loss of ambulation at a particular visit were assigned a score of 0.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Overall number of participants analyzed' signifies participants evaluable for this outcome measure.

Changes in activities of daily living and disease symptoms were captured via a DMD-specific survey administered by Site personnel. At screening or baseline, the participant and/or parent/caregiver were asked to identify any activities of daily living (for example, ambulation, balance, personal hygiene/grooming, dressing and undressing, self-feeding, using the bathroom, handwriting, school performance, behavior or energy level) or symptoms that were affected by the participant's DMD. At post-baseline visit (Week 48), the same participant and/or parent/caregiver was asked to describe any changes from baseline in those activities of daily living/symptoms, within the following categories: physical functioning; general energy level; cognition/school function; emotional/social functioning; and sleep. Changes from baseline were reported on a 5-point Likert scale: 1 (much worse), 2 (slightly worse), 3 (unchanged), 4 (slightly better), or 5 (much better).

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Number analyzed 'signifies participants evaluable for specified categories.

Changes in health-related quality of life (HRQL) were measured via the PODCI questionnaire that has been shown to correlate with disease progression and clinical outcome measures in DMD. 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 following PODCI domains were prespecified in the protocol for analysis:Transfers/Basic Mobility domain assesses difficulty experienced in performing routine motor activities in daily life. Sports/Physical Functioning domain assesses difficulty encountered in participating in more active recreational activities. Each domain was scored from 0 to 100, with 0 representing a poor outcome/worse health, while 100 representing the highest level of functioning and least pain.

ITT population included all participants who were randomized and received any study treatment; and had a valid baseline, and at least one valid post-baseline 6MWD value. Here, 'Overall number of participants analyzed' signifies participants evaluable for this outcome measure.

Plasma samples for the determination of ataluren concentrations were analyzed using a validated high performance liquid chromatography with tandem mass spectrometry (HPLC/MS-MS) method with a lower limit of quantitation of 0.5 micrograms/milliliter (mcg/mL).

As-treated population included all randomized participants who actually received any study treatment. Here, 'Number analyzed 'signifies participants evaluable at specified timepoint.

Study drug compliance was assessed by quantification of used and unused study drug. Compliance was assessed in terms of the percentage of drug actually taken relative to the amount that should have been taken during the study.

As-treated population included all randomized participants who actually received any study treatment.

An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. Serious adverse event (SAE) was an 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); persistent or significant disability/incapacity; congenital anomaly. AEs included both SAEs and non-serious AEs. Treatment-emergent adverse event (TEAE) was defined as an adverse event that occurred or worsened in the period extending from first dose of study drug to 6 weeks after the last dose of study drug. A summary of other non-serious AEs and all SAEs, regardless of causality is located in the 'Reported AE section'.

As-treated population included all randomized participants who actually received any study treatment.