Study of Ataluren (PTC124) in Cystic Fibrosis

Key Inclusion Criteria: * Ability to provide written informed consent (parental/guardian consent and participant assent if less than \[\<\] 18 years of age). * Evidence of completed participation in the double-blind study, PTC124-GD-009-CF (Study 009). * Body weight greater than or equal to (≥) 16 kilograms (kg). * Performance of a valid, reproducible spirometry test using the study-specific spirometer during the screening period. * Confirmed laboratory values within the central laboratory ranges at screening. * In male and female participants who are sexually active, willingness to abstain from sexual intercourse or employ a barrier or medical method of contraception during the study drug administration and 60-day follow-up period. * Willingness and ability to comply with all study procedures and assessments, including scheduled visits, drug administration plan, laboratory tests, and study restrictions. Key Exclusion Criteria: * Chronic use of systemic tobramycin within 4 weeks prior to screening. * Evidence of pulmonary exacerbation or acute upper or lower respiratory tract infection (including viral illnesses) within 3 weeks prior to screening or between screening and randomization. * Any change (initiation, change in type of drug, dose modification, schedule modification, interruption, discontinuation, or re-initiation) in a chronic treatment/prophylaxis regimen for CF or for CF-related conditions within 4 weeks prior to screening and randomization. * Known hypersensitivity to any of the ingredients or excipients of the study drug. * Exposure to another investigational drug within 4 weeks prior to screening. * Treatment with intravenous antibiotics within 3 weeks prior to screening. * History of solid organ or hematological transplantation. * Ongoing immunosuppressive therapy (other than corticosteroids). * Positive hepatitis B surface antigen, hepatitis C antibody test or human immunodeficiency virus (HIV) test. * Known portal hypertension. * Pregnancy or breast-feeding.