Patient inclusion has stopped after interim analysis.

Open-label study to investigate the effects of Orkambi in CF patients homozygous for the F508del mutation by functional respiratory imaging. Primary endpoints in this study are the changes in Specific airway volumes (siVaw) and Specific Airway resistance (siRaw). A total of 20 ORKAMBI-naive patients with Cystic Fibrosis, homozygous for the F508del mutation will be included in this open label study and will be followed through 3 months of treatment. The treatment will be started after all assessments are performed at visit 1. After the start of the treatment some baseline measurements will be repeated throughout the 3-month treatment period. The patient will be asked to visit the hospital monthly. All study visits should be scheduled around the same time.

Inclusion Criteria:

• Documented diagnosis of CF (homozygous for the F508del mutation must be present, this should be documented in the medical history).
• Age ≥ 12 years
• FEV1 > 50%
• Signed informed consent. If patient is a minor, parents/guardians must give written informed consent
• Patient must be on a stable regimen of CF medication for 4 weeks prior to Visit

Exclusion Criteria:

• FEV1 < 50%
• Anticipated requirement for hospitalization within the next three weeks
• History of pneumothorax within the past 6 months prior to Visit 1
• History of haemoptysis requiring embolization within the past 12 months prior to Visit 1
• Unable or unwilling to complete study visits or provide follow-up data as required per the study protocol
• Has taken Intravenous (IV) antibiotics within the past 4 weeks prior to Visit 1
• Has ongoing exacerbation or Allergic bronchopulmonary aspergillosis (ABPA)
• Pregnant or lactating female
• Posttransplant patients
• Patients with severe hepatic impairment