VX-770, a compound being developed by Vertex Pharmaceuticals Incorporated (Vertex) for the treatment of CF, is an orally bioavailable small molecule that targets the underlying defect in CF, the dysfunctional CFTR protein. In Phase 3 studies of VX-770 in patients with CF and a G551D CFTR mutation, improvements in CFTR function (measured by reduction in sweat chloride concentration) and improvements in lung function were observed.