1. MRC Centre for Drug Safety Science, Department of Molecular & Clinical Pharmacology, University of Liverpool, Liverpool L69 3GE, U.K.
2. GlaxoSmithKline, Park Road, Ware, Hertfordshire SG12 0DP, U.K.
3. Regional Adult Cystic Fibrosis Unit, St. James’s University Hospital, Leeds LS9 7TF, U.K.