Because dexamethasone also increases the biosynthesis of wt-CFTR [20] as well as the plasma membrane expression of wt-CFTR [18], [20](present study), the use of dexamethasone in CF patients receiving VX-770 [44], which activates G551D-CFTR in the plasma membrane, and VX-809 [45], which increases the amount of ΔF508-CFTR in the plasma membrane, should be considered to enhance the efficacy of VX-770 and VX-809. This evidence concerns the gene CFTR and cystic fibrosis.