A Precision Medicine Approach to Assess Protein Function Loss and the Potential for CFTR Function Restoration in Cystic Fibrosis and Related Disorders

This multicenter translational research study integrates diagnostic analyses and ex-vivo functional testing to support future clinical trials evaluating the safety and efficacy of CFTR modulator treatments in individuals with cystic fibrosis (CF) carrying rare or orphan mutations that may benefit from these therapies. Patient-derived nasal epithelial cells will be collected through standardized nasal brushing procedures, expanded, and cultured under air-liquid interface conditions to generate differentiated epithelia. Short-circuit current measurements will be used to assess baseline CFTR dysfunction and evaluate functional recovery following treatment with available CFTR modulators. These results will be complemented by DNA sequencing to identify complex alleles, quantitative and qualitative CFTR mRNA analyses to investigate gene expression and splicing defects, and assessments of epithelial transcriptomics, surface liquid viscosity, and mucociliary transport to identify additional mechanisms contributing to CF-like lung disease. The study will not include patient follow-up. The duration of participation will be limited to the time required to perform and analyze the nasal brushing procedure. Baseline CFTR activity will be compared with previously published data from individuals without cystic fibrosis.

Inclusion Criteria: * Adult or pediatric patients diagnosed with cystic fibrosis (CF) who have, on the first allele, a missense mutation or a small deletion (not resulting in a frameshift) that has not been functionally characterized or for which responsiveness to currently available therapies is limited or unknown, AND a second allele carrying another uncharacterized mutation, a stop-gain mutation, a class II mutation, or a large deletion of the CFTR gene; OR * Pediatric patients with Cystic Fibrosis Screen Positive, Inconclusive Diagnosis (CFSPID), meeting the following definition: "an asymptomatic newborn with a positive CF newborn screening (NBS) result and a sweat chloride concentration \