These are exciting times for the treatment of cystic fibrosis (CF). A completely new approach to drug treatment involves altering not the mutant gene itself, but the way the abnormal CF transmembrane conductance regulator (CFTR) protein functions within the cell. The first of these was Ivacaftor, which became available in 2012. It corrects the ‘gating defect’ at the cell membrane found in the 5% of CF patients with the p.Gly551Asp mutation (previously known as G551D), and has been highly effective in these. However on its own it is ineffective in …