⁃ Consent

⁃ A. Written informed consent (and assent when applicable) obtained from participant or participant's legal guardian

⁃ B. Is willing and able to adhere to the study visit schedule and other protocol requirements

⁃ Demographics

⁃ A. ≥ 12 years of age at Visit 1

⁃ Medical History

⁃ A. For persons of child-bearing potential: must not be pregnant at Visit 1 or plan to get pregnant during the 12-month study period

⁃ Disease History

⁃ A. 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 ≥ 60 mEq/liter by quantitative pilocarpine iontophoresis test (QPIT)

• Two well-characterized disease-causing pathogenic variants in the CFTR gene

⁃ or

• One well-characterized disease-causing mutation and a second CFTR variant (with variable or uncharacterized disease-causing potential) and sweat ≥ 30 mmol/liter with permission of the study sponsor-investigators

⁃ B. Clinically stable with no significant changes in health status within the 28 days prior to and including Visit 1

⁃ C. Does not have a history of lung transplantation

⁃ Concomitant Medications

⁃ A. Not genetically eligible for a CFTR modulator according to product label indications and/or No use of CFTR modulator for 28 days prior to Visit 1 with no intent to start or restart during the study period

⁃ B. No use of an investigational drug within 90 days prior to and including Visit 1

⁃ C. Not currently participating in an interventional drug or device trial. Participation in long-term safety follow-up studies (without redosing) and/or behavioral intervention trials is allowed.

⁃ D. No initiation of new chronic therapy (e.g., ibuprofen, azithromycin, inhaled tobramycin, Cayston®) within 28 days prior to and including Visit 1

⁃ E. No acute use of antibiotics (oral, inhaled or IV) or acute use of systemic corticosteroids for respiratory tract symptoms within 28 days prior to and including Visit 1