Long-Term Outcomes of Ataluren in Duchenne Muscular Dystrophy

This study is a long-term study of ataluren in participants with nonsense mutation Duchenne muscular dystrophy.

This study is a randomized, double-blind, placebo-controlled, 72-week study, followed by a 72-week open-label period. The purpose is to characterize the long-term effects of ataluren-mediated dystrophin restoration on disease progression. Participants will be randomized in a 1:1 ratio to ataluren or placebo. Participants will receive blinded study drug three times daily (TID) at morning, midday, and evening for 72 weeks, after which all participants will receive open-label ataluren for an additional 72 weeks (144 weeks in total). Study assessments will be performed at clinic visits every 12 weeks during the double-blind period and every 24 weeks during the open-label period. The total sample size of \~250 subjects will include \~160 subjects who meet the criteria for inclusion in the primary analysis population (age 7 to 16 years old, baseline six minute walk distance (6MWD) greater than or equal to (\>=) 300 meters, supine to stand \>= 5 seconds). The study will be conducted in the United States and other countries around the world.

Inclusion Criteria:

* Male sex
* Age ≥5 years
* Phenotypic evidence of Duchenne Muscular Dystrophy
* Nonsense point mutation in the dystrophin gene
* Use of systemic corticosteroids (prednisone/prednisolone or deflazacort)for a minimum of 12 months immediately prior to start of study treatment, with no significant change in dosage or dosing regimen for a minimum of 3 months immediately prior to start of study treatment
* 6MWD ≥150 meters
* Ability to perform timed function tests within 30 seconds
* Willingness and ability to comply with scheduled visits, drug administration plan, study procedures, laboratory tests, and study restrictions.

Exclusion Criteria:

* Any change in prophylaxis treatment for cardiomyopathy within 1 month prior to start of study treatment.
* Ongoing intravenous (IV) aminoglycoside or IV vancomycin therapy.
* Prior or ongoing therapy with ataluren.
* Known hypersensitivity to any of the ingredients or excipients of the study drug
* Exposure to another investigational drug within 6 months prior to start of study treatment, or ongoing participation in any interventional clinical trial.
* History of major surgical procedure within 12 weeks prior to start of study treatment, or expectation of major surgical procedure during the 72-week placebo-controlled treatment period.
* Requirement for daytime ventilator assistance or any use of invasive mechanical ventilation via tracheostomy.
* Uncontrolled clinical symptoms and signs of congestive heart failure
* Elevated serum creatinine or cystatin C at screening.