CFTR and cystic fibrosis: We have previously shown that in vivo treatment with vardenafil of F508del homozygous CF mice normalises CFTR-dependent chloride transport across the respiratory (Lubamba et al., 2008, 2011) and intestinal (Dhooghe et al., 2013) epithelia, and that it fully corrects F508del-CFTR trafficking and mislocalisation in mouse tissue sections (Dhooghe et al., 2013).