CHaractErizing CFTR Modulated Changes in Sweat Chloride and Their Association With Clinical Outcomes

Eligible subjects who have been prescribed and chronically taking a commercially approved
CFTR modulator for at least 3 months will be enrolled for a single visit to collect sweat to
be analyzed for SC at their local site laboratory. Limited clinical data obtained at this
visit will be augmented by retrospective and prospective data obtained from the CFFPR. Study
subjects who have been prescribed and switch to an alternative commercially approved CFTR
modulator will be approached to re-enroll in the study after being on the alternative
modulator for at least 3 months so that a new SC value can be obtained.

Inclusion Criteria:

- Written informed consent (and assent when applicable) obtained from subject or
subject's legal representative

- Enrolled in the CFF Patient Registry

- Male or female ≥ 4 months of age on day of study visit

- Documentation of a CF diagnosis as evidenced by one or more clinical features
consistent with the CF phenotype and one or more of the following criteria:

- Sweat chloride equal to or greater than 60 mEq/liter by quantitative pilocarpine
iontophoresis test (QPIT)

- Two well-characterized mutations in the cystic fibrosis transmembrane conductance
regulator (CFTR) gene

- Current treatment with a prescribed commercially approved CFTR modulator for at least
3 months prior to enrollment

- Able to perform the testing and procedures required for this study, as judged by the
investigator

Exclusion Criteria:

- 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

- Currently enrolled in an investigational trial (including open-label follow-on studies
and EAPs) of an agent expected to have an impact on sweat chloride (refer to current
list provided on study website)