Second, we generated primary nasal epithelial cultures from patients with CF homozygous for the F508del mutation, cultured them at air-liquid interface (ALI) in 2 commonly used cell culture media (UNC-ALI medium vs. PneumaCult medium), and studied the impact of acute versus chronic ivacaftor treatment as part of ETI on restoration of F508del-CFTR–mediated chloride secretion by transepithelial bioelectric measurements. This evidence concerns the gene CFTR and cystic fibrosis.