An orally available compound identified by high-throughput screening, the CFTR potentiator VX-770 (Ivacaftor, trade name Kalydeco), has been shown to efficiently reduce chloride levels in sweat and to improve lung function in CF patients harboring the G551D CFTR genotype, a rare class III CFTR mutant that affects only 4–5 % of CF patients [7, 8]. Here, CFTR is linked to cystic fibrosis.