The Cystic Fibrosis Foundation and Vertex Pharmaceuticals have announced promising results from a phase III clinical trial of VX-770, an investigational oral therapy that targets a defective protein that causes cystic fibrosis (CF).

The placebo controlled trial involved 161 patients aged 12 years and above, who carry at least one copy of a CF mutation called G551D (which affects only 4% of CF patients) and found that VX-770 improved lung function by 10.5% compared with placebo at 24 and 48 weeks, and by about 17% from baseline. Patients also showed improvement across all key secondary endpoints in the study: they were 55% less likely to need treatment with an antibiotic due to worsening lung symptoms, and had reductions in sweat chloride (excessive sweat chloride is a clinical indicator of CF) and patients gained on average nearly 3.2 kg in bodyweight. Discontinuations due to adverse effects were less frequent among those treated with VX-770 (1% vs. 5% in placebo group).

Vertex said it will file for U.S. and European approval of the drug in the second half of 2011. VX-770 is currently being tested in combination with another drug, VX-809, in cystic fibrosis patients with the most common CF mutation, Delta F508a.