A new study has confirmed that the drug, ivacaftor (VX-770), significantly improves lung function in some people with cystic fibrosis. The oral medicine targets the defective protein produced by the gene mutation called G551D that causes CF. Researchers found that patients carrying G551D — approximately four per cent of all CF patients — who were treated with VX-770 showed a 17 per cent relative improvement in lung function that was sustained over the course of 48 weeks.