Study of GLPG1837 in Subjects With Cystic Fibrosis (S1251N Mutation)

At least 6 cystic fibrosis patients with the S1251N mutation will be treated for 4 weeks, consisting of two consecutive treatment periods of two weeks evaluating one dose of GLPG1837 each. After the treatment period, there is a 7-10 days follow-up period. During the course of the study, subjects will be examined for any side effects that may occur (safety and tolerability). Changes in sweat chloride will be assessed as biomarker from baseline onwards, and changes in pulmonary function (efficacy) will be explored throughout the study. The amount of GLPG1837 present in the blood (pharmacokinetics) will also be determined.