: TRANSITION: An Observational Study of Transition From Lumacaftor/Ivacaftor to Tezacaftor/Ivacaftor (Tez/Iva)

Inclusion Criteria:

- Confirmed diagnosis of CF

- Male or female subjects greater than or equal to 12 years of age

- Ability to reproducibly perform spirometry testing

- Physician decision to treat with tezacaftor/ivacaftor (Smydeko)

- Ability to understand and sign a written informed consent or assent and comply with
the requirements of the study

- Continuous use of orkambi for at least 1 month prior to visit 1

Exclusion Criteria:

- History of hypersensitivity to tezacaftor and/or ivacaftor

- Presence of a condition or abnormality that in the opinion of the Investigator would
compromise the safety of the patient or the quality of the data

- Any acute lower respiratory symptoms treated with oral, inhaled or intravenous
antibiotics (IV) or systemic corticosteroids within the 2 weeks prior to Visit 1

- Major or traumatic surgery within 12 weeks prior to Visit 1

- For women of child-bearing potential: a positive pregnancy test at Visit 1

- Unable or unwilling to fast (including no enteric tube feedings) for at least 6 hours
prior each visit

- Initiation of any new chronic therapy within 4 weeks prior to Visit 1

- Use of an investigational agent within 28 days prior to Visit 1

- Use of chronic oral corticosteroids within 28 days prior to Visit 1

- Treatment for nontuberculous mycobacterial (NTM) infection, consisting of greater than
or equal to two antibiotics (oral, IV, and/or inhaled) within 28 days prior to Visit 1

- History of lung or liver transplantation, or listing for organ transplantation