HRH1 and cystic fibrosis: Conversely, the non-cystic-fibrosis-related drug Azelastine, a selective histamine-H1 receptor antagonist used in the symptomatic treatment of allergic rhinitis, which has the same octanol/water partition coefficient as Lumacaftor (logP = 4.4), did not exert a rescuing activity on the mutant hairpin (Supplementary Fig. 8), indicating specificity of Lumacaftor action on the TM3/4 segment.