GLPG2737 on Top of Orkambi in Subjects With Cystic Fibrosis

Inclusion Criteria: * Male or female subject ≥18 years of age on the day of signing the ICF. * A confirmed clinical diagnosis of CF and homozygous for the F508del CFTR mutation. * Stable intake of physician prescribed Orkambi (lumacaftor 400 mg/ivacaftor 250 mg b.i.d.) for at least 12 weeks prior to the first study drug administration, and planned continuation of Orkambi for the duration of the study. * FEV1 ≥40% of predicted normal for age, gender and height at screening (pre- or postbronchodilator). * Sweat chloride concentration ≥60 mmol/L at screening. Exclusion Criteria: * History of serious allergic reaction to any drug as determined by the investigator (e.g., anaphylaxis requiring hospitalization) and/or known sensitivity to any component of the study drug. * History of clinically meaningful unstable or uncontrolled chronic disease that makes the subject unsuitable for inclusion in the study in the opinion of the investigator. * Unstable pulmonary status or respiratory tract infection (including rhinosinusitis) requiring a change in therapy within 4 weeks prior to the first study drug administration. * History of hepatic cirrhosis with portal hypertension (e.g.,signs/symptoms of splenomegaly, esophageal varices, etc.). * Abnormal liver function test at screening, defined as aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) and/or alkaline phosphatase and/or gammaglutamyl transferase (GGT) ≥3 x the upper limit of normal (ULN), and/or total bilirubin ≥1.5 x the ULN at screening.