Vertex Pharmaceuticals announced positive results from its Phase 3 ENVISION study of VX-770 for the treatment of cystic fibrosis (CF) among children ages 6–11 with at least one copy of the G551D mutation in the CFTR gene. In the study, 52 children were enrolled and received VX-770 as a single 150mg tablet every 12 hours or placebo. At the time of this analysis, the last patients had completed their Week 40 visit. All children who remain on this study will be followed through 48 weeks. The study met its primary endpoint of mean absolute change from baseline in percent predicted FEV1 through Week 24. A difference in mean absolute improvement from baseline in lung function of 12.5% and a difference in mean relative improvement from baseline in lung function of 17.4% compared to placebo (p<0.0001) were observed through Week 24.

Cystic fibrosis is caused by defective or missing CFTR proteins, which result in poor ion flow across cell membranes, including in the lung, and the accumulation of abnormally thick, sticky mucus that leads to chronic lung infections and progressive lung damage. In people with the G551D mutation, CFTR proteins do not function normally at the cell surface. VX-770 is an orally available drug that directly targets the defective CFTR protein known to cause CF. VX-770 increases the function of the defective CFTR protein by increasing the gating activity of CFTR once it reaches the cell surface. 

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