About 5% of people with cystic fibrosis have a glycine-for-aspartic acid substitution at amino acid 551 in the cystic fibrosis transmembrane conductance regulator gene (G551D-CFTR). With this mutation CFTR protein reaches the cell surface but its chloride transport function is defective. The new drug, VX-770, is an orally active potentiator of the CFTR protein; it increases the activity of both normal and defective CFTR protein in vitro, but particularly in cells with G551D-CFTR. Now (New England Journal of Medicine 2010;363:1991–2003; see also editorial, ibid:2056–8) a multicentre US phase II trial has provided encouragement for further clinical studies of VX-770. The study included 39 subjects aged at least 18 years with cystic fibrosis and at least one G551D-CFTR allele. Twenty subjects entered a crossover trial with two 14-day study periods and randomisation to VX-770 at doses of 25, 75 or 150 mg, or placebo, every 12 h. Nineteen subjects entered a 28-day parallel-group, placebo-controlled trial. Adverse events occurred at a similar rate in the VX-770 and placebo groups, none required discontinuation of the drug and all resolved during the study. There were significant within-s8bject improvements in nasal potential difference and reductions in sweat chloride with VX-770. There were also significant within-subject improvements in forced expiratory volume in 1 s. Further studies are merited.

Pandemic influenza A H1N1 …