Ivacaftor in subjects with cystic fibrosis who are homozygous for the F508del-CFTR mutation

• Published in: Chest Vol. 142; no. 3; p. 718
• Main Authors: Flume, Patrick A, Liou, Theodore G, Borowitz, Drucy S, Li, Haihong, Yen, Karl, Ordoñez, Claudia L, Geller, David E
• Format: Journal Article
• Language: English
• Published: United States 01.09.2012
• Subjects: Adolescent; Adult; Alleles; Aminophenols - therapeutic use; Biomarkers - analysis; Child; Chlorides - analysis; Cystic Fibrosis - drug therapy; Cystic Fibrosis - genetics; Cystic Fibrosis Transmembrane Conductance Regulator - genetics; Double-Blind Method; Female; Homozygote; Humans; Male; Middle Aged; Mutation - genetics; Pharmacogenetics; Quinolones - therapeutic use; Sweat - chemistry; Treatment Outcome; Young Adult
• ISSN: 1931-3543
• DOI: 10.1378/chest.11-2672

Ivacaftor (VX-770) is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator that was approved in the United States for the treatment of cystic fibrosis (CF) in patients ≥ 6 years of age who have a G551D mutation; however, the most prevalent disease-causing CFTR mutation, F508del, causes a different functional defect. The objectives of this study were to evaluate the safety of ivacaftor in a larger population and for a longer time period than tested previously and to assess the efficacy of ivacaftor in subjects with CF who are homozygous for F508del-CFTR. This was a phase 2 study with a 16-week randomized (4:1), double-blind, placebo-controlled period (part A) and an open-label extension (part B) for subjects who met prespecified criteria. Part A: The safety profile of ivacaftor was comparable to that of the placebo. The overall adverse event frequency was similar in the ivacaftor (87.5%) and placebo (89.3%) groups through 16 weeks. The difference in the change of FEV₁ % predicted from baseline through week 16 (primary end point) between the ivacaftor and placebo groups was 1.7% (P = .15). Sweat chloride, a biomarker of CFTR activity, showed a small reduction in the ivacaftor vs placebo groups of -2.9 mmol/L (P = .04) from baseline through week 16. Part B: No new safety signals were identified. The changes in FEV₁ or sweat chloride in part A were not sustained with ivacaftor treatment from week 16 to week 40. These results expand the safety information for ivacaftor and support its continued evaluation. Lack of a clinical effect suggests that a CFTR potentiator alone is not an effective therapeutic approach for patients who have CF and are homozygous for F508del-CFTR. ClinicalTrials.gov; No.: NCT00953706; URL: www.clinicaltrials.gov.