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N Engl J Med. 2019 Nov 7;381(19):1809-1819. doi: 10.1056/NEJMoa1908639. Epub 2019 Oct 31.

Elexacaftor-Tezacaftor-Ivacaftor for Cystic Fibrosis with a Single Phe508del Allele.

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From the Department of Respiratory and Sleep Medicine, Westmead Hospital and CF Research Group, Ludwig Engel Centre for Respiratory Research, Westmead Institute for Medical Research, University of Sydney, Westmead, NSW, Australia (P.G.M.); the Department of Pediatric Pulmonology, Immunology, and Intensive Care Medicine, Charité-Universitätsmedizin Berlin, the Berlin Institute of Health, and the German Center for Lung Research, Berlin (M.A.M.); the Department of Medical Microbiology, Department of Pediatrics, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic (P.D.); the Pediatric Respiratory Medicine and Pediatric Cystic Fibrosis Clinic, McGill University Health Centre, Montreal (L.C.L.); St. Vincent's University Hospital and University College Dublin School of Medicine, Dublin (E.F.M.); the Department of Internal Medicine, University of Kansas Medical Center, Kansas City (D.P.); the Department of Pediatrics, University of Washington School of Medicine, and Seattle Children's Research Institute, Seattle (B.W.R.); the Departments of Medicine and Pediatrics, National Jewish Health, Denver (J.L.T.-C.); the Division of Respirology, St. Michael's Hospital, University of Toronto, Toronto (E.T.); the Cystic Fibrosis Reference Center, Department of Pediatrics, Catholic University of Leuven, Leuven, Belgium (F.V.); Vertex Pharmaceuticals, Boston (G.M., C.M.M., S.M.M., N.N., J.S., C.S., S.T., D.W., F.X.); the Departments of Medicine, Pediatrics, and Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham (S.M.R.); and the Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas (R.J.).



Cystic fibrosis is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein, and nearly 90% of patients have at least one copy of the Phe508del CFTR mutation. In a phase 2 trial involving patients who were heterozygous for the Phe508del CFTR mutation and a minimal-function mutation (Phe508del-minimal function genotype), the next-generation CFTR corrector elexacaftor, in combination with tezacaftor and ivacaftor, improved Phe508del CFTR function and clinical outcomes.


We conducted a phase 3, randomized, double-blind, placebo-controlled trial to confirm the efficacy and safety of elexacaftor-tezacaftor-ivacaftor in patients 12 years of age or older with cystic fibrosis with Phe508del-minimal function genotypes. Patients were randomly assigned to receive elexacaftor-tezacaftor-ivacaftor or placebo for 24 weeks. The primary end point was absolute change from baseline in percentage of predicted forced expiratory volume in 1 second (FEV1) at week 4.


A total of 403 patients underwent randomization and received at least one dose of active treatment or placebo. Elexacaftor-tezacaftor-ivacaftor, relative to placebo, resulted in a percentage of predicted FEV1 that was 13.8 points higher at 4 weeks and 14.3 points higher through 24 weeks, a rate of pulmonary exacerbations that was 63% lower, a respiratory domain score on the Cystic Fibrosis Questionnaire-Revised (range, 0 to 100, with higher scores indicating a higher patient-reported quality of life with regard to respiratory symptoms; minimum clinically important difference, 4 points) that was 20.2 points higher, and a sweat chloride concentration that was 41.8 mmol per liter lower (P<0.001 for all comparisons). Elexacaftor-tezacaftor-ivacaftor was generally safe and had an acceptable side-effect profile. Most patients had adverse events that were mild or moderate. Adverse events leading to discontinuation of the trial regimen occurred in 1% of the patients in the elexacaftor-tezacaftor-ivacaftor group.


Elexacaftor-tezacaftor-ivacaftor was efficacious in patients with cystic fibrosis with Phe508del-minimal function genotypes, in whom previous CFTR modulator regimens were ineffective. (Funded by Vertex Pharmaceuticals; VX17-445-102 number, NCT03525444.).

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