['cystic fibrosis']
['vx-809', 'placebo', 'vx-770']

        Inclusion Criteria:

          -  Subjects who weigh ≥15 kg without shoes a the Screening Visit

          -  Subjects with confirmed diagnosis of CF at the Screening Visit.

          -  Subjects who are homozygous for the F508del CFTR mutation

          -  Subjects with ppFEV1 of ≥70 percentage points adjusted for age, sex, and height

          -  Subjects with a screening LCI2.5 result greater than or equal to 7.5

        Exclusion Criteria:

          -  History of any comorbidity reviewed at the Screening Visit that, in the opinion of the
             investigator, might confound the results of the study or pose an additional risk in
             administering study drug to the subject.

          -  Any clinically significant laboratory abnormalities at the Screening Visit that would
             interfere with the study assessments or pose an undue risk for the subject

          -  Clinically significant abnormalities in hemoglobin, liver function, or renal function
             at the Screening Visit.

          -  An acute upper or lower respiratory infection, pulmonary exacerbation, or changes in
             therapy for pulmonary disease within 28 days before Day 1

          -  History of solid organ or hematological transplantation at the Screening Visit
      