This study investigates the relationship between CFTR modulator blood concentrations and adverse events in individuals with cystic fibrosis (CF). CFTR modulators are medications that help manage CF, a genetic disorder affecting the lungs and digestive system. The study focuses on understanding if different levels of these medications in the blood are linked to side effects, known as adverse events (AEs).

Participants will undergo a 12-hour observational study visit where various tests will be conducted. These include blood sampling at multiple intervals to measure drug concentrations, a sweat chloride test to assess CF impact, and genetic testing to understand drug metabolism. Participants will also complete questionnaires to evaluate mental health and quality of life, and provide detailed medication histories to identify potential drug interactions.

• Who can participate: Participants must be 12 years or older, currently taking CFTR modulators, and either tolerating the medication or experiencing adverse events. Those taking medications interacting with CFTR modulators are excluded.
• Study details: Participants will receive a standardized high-fat meal with their medication and have blood samples taken to measure drug levels. They will also complete mental health and quality of life questionnaires.
• Study visits: The study requires 1 visit.