Inclusion Criteria:

   - Evidence of signed and dated informed consent/assent document(s) indicating that the
   subject (and/or his parent/legal guardian) has been informed of all pertinent aspects
   of the trial

   - Age >=6 years.

   - Body weight >=16 kg.

   - Sweat chloride >60 milliequivalent per liter (mEq/L)

   - Documentation of the presence of a nonsense mutation in at least 1 allele of the
   cystic fibrosis transmembrane conductance regulator (CFTR) gene, as determined by
   genotyping performed at a laboratory certified by the College of American Pathologists
   (CAP), or under the Clinical Laboratory Improvement Act/Amendment (CLIA), or by an
   equivalent organization

   - Verification that a blood sample has been drawn for sequencing of the CFTR gene

   - Ability to perform a valid, reproducible spirometry test using the study-specific
   spirometer with demonstration of an FEV1 >=40% and <=90% of predicted

   - Demonstration at Visit 2 of a valid %-predicted FEV1 within 15% of the Screening %
   predicted FEV1 value

   - Resting oxygen saturation (as measured by pulse oximetry) >=92% on room air.

   - Confirmed screening laboratory values within pre-specified ranges

   - In subjects 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, study procedures, laboratory tests, and
   study restrictions

Exclusion Criteria:

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

   - Previous participation in the Phase 3 trial of ataluren (PTC124-GD-009-CF).

   - Any change (initiation, change in type of drug, dose modification, schedule
   modification, interruption, discontinuation, or re-initiation) in a chronic
   treatment/prophylaxis regimen for Cystic Fibrosis (CF) or for CF-related conditions
   within 4 weeks prior to screening

   - Chronic use of inhaled aminoglycosides (eg, tobramycin) or use of inhaled
   aminoglycosides within 4 weeks prior to screening.

   - Exposure to another investigational drug within 4 weeks prior to screening

   - Ongoing participation in any other therapeutic clinical trial

   - Evidence of pulmonary exacerbation or acute upper or lower respiratory tract infection
   (including viral illnesses) within 3 weeks prior to screening

   - Treatment with intravenous antibiotics within 3 weeks prior to screening

   - Ongoing immunosuppressive therapy (other than corticosteroids)

   - Ongoing warfarin, phenytoin, or tolbutamide therapy

   - History of solid organ or hematological transplantation

   - Major complications of lung disease (including massive hemoptysis, pneumothorax, or
   pleural effusion) within 8 weeks prior to screening

   - Known portal hypertension

   - Positive hepatitis B surface antigen, hepatitis C antibody test, or human
   immunodeficiency virus (HIV) test

   - Pregnancy or breast-feeding

   - Current smoker or a smoking history of >=10 pack-years (number of cigarette packs/day
   x number of years smoked).

   - Prior or ongoing medical condition (eg, concomitant illness, alcoholism, drug abuse,
   psychiatric condition), medical history, physical findings, electrocardiogram (ECG)
   findings, or laboratory abnormality that, in the investigator's opinion, could
   adversely affect the safety of the subject, makes it unlikely that the course of
   treatment or follow-up would be completed, or could impair the assessment of study
   results