CF patients enrolled in this protocol will be recruited from patients followed by the Adult CF Program at National Jewish Health. Patients will be selected based on planned use of a CFTR modulator by their primary physician. No patient will be started on (or will switch) CFTR modulator agents for the purpose of the study. After enrollment, biological samples may be collected at two different time points prior to treatment initiation. One set of samples will be collected at baseline health prior to CFTR modulator initiation or change. A second set of samples will be obtained in subjects at the time of acute pulmonary exacerbation, if one occurs prior to CFTR modulator initiation or change. Post CFTR modulator initiation study assessments will be obtained at least one month after starting treatment and continue up to 2 times a year (including during pulmonary exacerbations), in order to document longitudinal effects of therapies and changes in inflammatory biology over time. At the time of each biological sampling, blood, sputum sample, urine, and a quality of life assessment will be acquired in all enrolled subjects. In addition to demographic data, clinical data, such as quantitative microbiology and simple spirometry will be recorded at the time of sample collection.

Inclusion Criteria:

• Documented diagnosis of CF with an eligible mutation for modulator treatment.
• Age 18 years old or older.
• Patient is starting a CFTR modulator as part of their clinical care or switching CFTR modulator therapy agents, pending FDA approval.
• Ability to perform reproducible Pulmonary Function Tests.
• Willingness to comply with study procedure and willingness to provide written consent.

Exclusion Criteria:

• Presence of a condition or abnormality that, in the opinion of the Principal Investigator (PI), would compromise the safety of the patient or the quality of the data.

Subjects enrolled in this protocol will be recruited from patients followed by the Adult CF Program at National Jewish Health. The investigators project enrolling 80 subjects with diagnosed CF, 18 years of age or older, with eligible mutations for CFTR modulator therapies. Concomitant use of systemic steroids will be allowed, and typical co-infections or co-morbidities will not result in exclusion.