144 Effect of treatment with ivacaftor on exhaled nitric oxide

Abstract

Objectives: Nitric oxide (NO) is reduced in cystic fibrosis (CF) airways and NO deficiency may contribute to CF lung disease. Previous studies have shown that antibiotic treatment for CF pulmonary exacerbations resulted in an increase in airway NO formation. Ivacaftor is the first CFTR-targeting drug that was approved for the treatment of people with CF and certain CFTR gating mutations. Methods: We studied the effect of ivacaftor treatment on airway NO in people with CF in an observational trial. The study was approved by the pediatric and adult study site Institutional Research Ethics Boards. Results: So far, a total of 12 (8 pediatric and 4 adult) patients with CF were recruited. All carried at least one copy of the Gly551Asp-CFTR mutation. Mean age at enrolment was 20 (range 6-50) years. Pulmonary function (spirometry) and fraction of exhaled NO (FENO50) were measured before and 4 weeks after initiation of ivacaftor treatment. Both mean (±SD) forced vital capacity (93.4±11.6 vs 100.9±9.1% of predicted, p = 0.004) and forced expiratory volume in one second (FEV1) (71.6±16.0 vs 83.3±16.2% of predicted, p = 0.002) improved with treatment. FENO increased in all but one of the study participants (p <0.01, Wilcoxon test). Mean FENO doubled from 8.25±5.35 ppb before to 16.84±17.32 ppb after initiation of ivacaftor treatment. There was no correlation between the changes in pulmonary function test results and FENO. Conclusion: Four weeks of treatment with ivacaftor resulted in a significant increase in pulmonary function and airway NO formation. These data suggest that CFTRtargeting therapies may result in reconstitution of impaired airway NO formation in patients with CF.