Potentiators of Defective ΔF508-CFTR Gating that Do Not Interfere with Corrector Action

Combination drug therapies under development for cystic fibrosis caused by the Delta F508 mutation in cystic fibrosis transmembrane conductance regulator (CFTR) include a "corrector" to improve its cellular processing and a "potentiator" to improve its chloride channel function. Recently, it was reported that the approved potentiator N-(2,4-di-tert-butyl-5-hydroxyphenyl)4-oxo-1,4-dihydroquinoline-3-carboxamide (Ivacaftor) reduces Delta F508-CFTR cellular stability and the efficacy of investigational correctors, including 3-(6-[([1-(2,2-difluoro-1,3-benzodioxol-5-yl)cyclopropyl] carbonyl) amino]-3-methyl-2-pyridinyl)-benzoic acid and 1-(2,2-difluoro-1,3-benzodioxol-5-yl)-N-(1-[(2R)-2,3-dihydroxypropyl]-6-fluoro-2-(2-hydroxy-1,1-dimethylethyl)-1-Hindol-5-yl), which might contribute to the modest reported efficacy of combination therapy in clinical trials. Here, we report the identification and characterization of potentiators that do not interfere with Delta F508-CFTR stability or corrector action. Highthroughput screening and structure-activity analysis identified several classes of potentiators that do not impair corrector action, including tetrahydrobenzothiophenes, thiooxoaminothiazoles, and pyrazole-pyrrole-isoxazoles. The most potent compounds have an EC50 for Delta F508-CFTR potentiation down to 18 nM and do not reduce corrector efficacy in heterologous Delta F508-CFTR-expressing cells or primary cultures of Delta F508/Delta F508 human bronchial epithelia. The Delta F508-CFTR potentiators also activated wild-type and G551D CFTR, albeit weakly. The efficacy of combination therapy for cystic fibrosis caused by the Delta F508 mutation may be improved by replacement of Ivacaftor with a potentiator that does not interfere with corrector action.