FDA rejects expanded use of Vertex's cystic fibrosis drug

(Reuters) - The U.S. Food and Drug Administration has denied the expanded use of Vertex Pharmaceutical Inc's bestseller, Kalydeco, in certain cystic fibrosis patients, the company said on Friday. The regulator rejected the company's application for using the drug in cystic fibrosis patients aged 2 or older, who have one of 23 residual function mutations. [ The company's shares fell 7.7 pct to $9.60 in premarket trading. Cystic fibrosis is caused by a defective gene that disrupts the function of the lungs and digestive system, producing a build-up of thick, sticky mucus leading to inflammation and recurrent bacterial infections. Half of the people with cystic fibrosis live longer than 28 years, according to the World Health Organization.(https://bit.ly/1OqUj6Z) (Corrects fourth paragraph to "Half of the people with cystic fibrosis live longer than 28 years, according to the World Health Organization", from "Most patients die in their mid-20s") (Reporting by Amrutha Penumudi in Bengaluru; Editing by Maju Samuel)