title: Mechanistic Approaches to Improve Correction of the Most Common Disease-Causing Mutation in Cystic Fibrosis.
abstract: The most common mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene leads to deletion of the phenylalanine at position 508 (ΔF508) in the CFTR protein and causes multiple folding and functional defects. Contrary to large-scale efforts by industry and academia, no significant therapeutic benefit has been achieved with a single "corrector". Therefore, investigations concentrate on drug combinations. Orkambi (Vertex Pharmaceuticals), the first FDA-approved drug for treatment of cystic fibrosis (CF) caused by this mutation, is a combination of a corrector (VX-809) that facilitates ΔF508 CFTR biogenesis and a potentiator (VX-770), which improves its function. Yet, clinical trials utilizing this combination showed only modest therapeutic benefit. The low efficacy Orkambi has been attributed to VX-770-mediated destabilization of VX-809-rescued ΔF508 CFTR. Here we report that the negative effects of VX-770 can be reversed by increasing the half-life of the endoplasmic reticulum (ER) form (band B) of ΔF508 CFTR with another corrector (Corr-4a.) Although Corr-4a alone has only minimal effects on ΔF508 CFTR rescue, it increases the half-life of ΔF508 CFTR band B when it is present during half-life measurements. Our data shows that stabilization of band B ΔF508 CFTR with Corr-4a and simultaneous rescue with VX-809, leads to a >2-fold increase in cAMP-activated, CFTRinh-172-inhibited currents compared to VX-809 alone, or VX-809+VX-770. The negative effects of VX-770 and the Corr-4a protection are specific to the native I507-ATT ΔF508 CFTR without affecting the inherently more stable, synonymous variant I507-ATC ΔF508 CFTR. Our studies emphasize that stabilization of ΔF508 CFTR band B in the ER might improve its functional rescue by Orkambi.
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Vedrana
authors.initials: V
authors.lastname: Bali
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Lung Injury and Repair Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Lazrak
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Purushotham
authors.initials: P
authors.lastname: Guroji
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Lung Injury and Repair Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Sadis
authors.initials: S
authors.lastname: Matalon
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|The Lung Injury and Repair Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Bebok
mesh_terms: D000627:Aminophenols / Q000494:pharmacology*; D000631:Aminopyridines / Q000494:pharmacology*; D001549:Benzamides / Q000494:pharmacology*; D052117:Benzodioxoles / Q000494:pharmacology*; D002460:Cell Line; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000187:drug effects / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006207:Half-Life; D006801:Humans; D009154:Mutation; D015363:Quinolones / Q000494:pharmacology*; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D000627:Aminophenols; D000631:Aminopyridines; D001549:Benzamides; D052117:Benzodioxoles; C505032:CFTR protein, human; C561871:N-(2-5-chloro-2-methoxyphenylamino)4'-methyl(4,5''bithiazolyl-2'-yl)benzamide; D015363:Quinolones; D013844:Thiazoles; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C545203:ivacaftor; C569105:lumacaftor