Study to Evaluate Biological & Clinical Effects of Significantly Corrected CFTR Function in Infants & Young Children

Inclusion Criteria:

• Part A:

  • Less than 10 years of age at the first study visit.
  • Documentation of a CF diagnosis.

Part B:

• Participated in Part A OR less than 7 years of age at the first study visit.
• Documentation of a CF diagnosis.
• CFTR mutations consistent with FDA labeled indication of highly effective modulator therapy (ivacaftor or elexacaftor/tezacaftor/ivacaftor).
• Physician intent to prescribe ivacaftor or elexacaftor/tezacaftor/ivacaftor.

Exclusion Criteria:

• Part A and Part B:
• Use of an investigational drug within 28 days prior to and including the first study visit.
• Use of ivacaftor or elexacaftor/tezacaftor/ivacaftor within the 28 days prior to and including the first study visit.
• Use of chronic oral corticosteroids within the 28 days prior to and including the first study visit.