CFTR and cystic fibrosis: Previously, it was found that the p.Leu467Phe variant does not lead to the development of CF, but reduces the amount of functional (fully glycosylated) CFTR by two times compared to the norm [55], but p.Leu467Phe in combination with p.Phe508del causes a lack of response to treatment with CFTR correctors [20].