Inclusion Criteria:

   - Ability to provide written informed consent (parental/guardian consent if
   applicable)/assent per local requirements.

   - Phenotypic evidence of dystrophinopathy based on the onset of characteristic clinical
   symptoms or signs (for example; proximal muscle weakness, waddling gait, and Gowers'
   maneuver) by 6 years of age, an elevated serum creatinine kinase level, and ongoing
   difficulty with walking.

   - Documentation of the presence of a nonsense point mutation in the dystrophin gene as
   determined by gene sequencing from a laboratory certified by the College of American
   Pathologists (CAP), the Clinical Laboratory Improvement Act/Amendment (CLIA) or an
   equivalent organization.

   - Documentation that a blood sample has been drawn for confirmation of the presence of a
   nonsense mutation in the dystrophin gene.

   - Use of systemic corticosteroids (prednisone, prednisolone, or deflazacort) for a
   minimum of 6 months immediately prior to start of study treatment, with no significant
   change in dosage or dosing regimen (not related to body weight change) for a minimum
   of 3 months immediately prior to start of study treatment and a reasonable expectation
   that dosage and dosing regimen will not change significantly for the duration of the
   study.

   - Valid Screening 6-minute walk distance (6MWD) greater than or equal to (≥) 150 meters.
   Valid Screening 6MWD must have been less than or equal to (≤) 80% of predicted for age
   and height.

   - Results of the 2 Baseline 6MWD results must be determined as valid and results of the
   Day 2 Baseline 6MWD must be within 20% of the Day 1 Baseline 6MWD.

   - Baseline 6MWD (mean of valid Day 1 and Day 2 values) must be no more than a 20% change
   from the valid Screening 6MWD.

   - Confirmed screening laboratory values within the central laboratory ranges (hepatic,
   renal, and serum electrolyte parameters).

   - Willingness to abstain from sexual intercourse or employ an approved method of
   contraception during the period of study drug administration and 6-week follow-up
   period.

   - Willingness and ability to comply with scheduled visits, drug administration plan,
   study procedures, laboratory tests, and study restrictions.

Exclusion Criteria:

   - Treatment with systemic aminoglycoside antibiotics within 3 months prior to start of
   study treatment.

   - Initiation of systemic corticosteroids therapy within 6 months prior to start of study
   treatment.

   - Change in systemic corticosteroid therapy (for example; change in type of drug, dose
   modification not related to body weight change, schedule modification, interruption,
   or reinitiation) within 3 months prior to start of study treatment.

   - Any change (initiation, change in type of drug, dose modification, schedule
   modification,interruption, discontinuation, or reinitiation) in prophylaxis/treatment
   for congestive heart failure (CHF) within 3 months prior to start of study treatment.

   - Ongoing use of coumarin-based anticoagulants (for example; warfarin), phenytoin,
   tolbutamide, or paclitaxel.

   - Prior therapy with ataluren.

   - Known hypersensitivity to any of the ingredients or excipients of the study drug.

   - Exposure to another investigational drug within 3 months prior to start of study
   treatment.

   - History of major surgical procedure within 6 weeks prior to start of study treatment.

   - Ongoing immunosuppressive therapy (other than corticosteroids).

   - Ongoing participation in any clinical trial (except for studies specifically approved
   by PTC Therapeutics).

   - Expectation of major surgical procedure (for example; scoliosis surgery) during the
   12-month treatment period of the study.

   - Requirement for daytime ventilator assistance.

   - Uncontrolled clinical symptoms and signs of CHF (American College of
   Cardiology/American Heart Association Stage C or Stage D).

   - Prior or ongoing medical condition (for example; concomitant illness, psychiatric
   condition, behavioral disorder, alcoholism, drug abuse), medical history, physical
   findings (for example; lower limb injury that may affect 6MWT performance),
   electrocardiogram (ECG) findings, or laboratory abnormality that, in the
   investigator's opinion, could adversely affect the safety of the participant, makes it
   unlikely that the course of treatment or follow-up would be completed, or could impair
   the assessment of study results.