Ivacaftor led to significant clinical improvements in CF patients carrying the p.Ser549Arg mutation, including: Better pulmonary function, restoration of CFTR function, improved BMI and glucose metabolism. The drug did not eliminate chronic infections but reduced the need for intravenous antibiotics.This study supports the efficacy of Ivacaftor for this rare mutation, reinforcing its clinical use. Here, CFTR is linked to cystic fibrosis.