FDA expanded on Wednesday the approved use of ivacaftor (Kalydeco—Vertex Pharmaceuticals) for treating cystic fibrosis. The decision expands the number of rare gene mutations that the drug can now treat from 10 mutations to 33. The decision was based, in part, on the results of laboratory testing, which FDA used in conjunction with evidence from earlier human clinical trials. "Many rare cystic fibrosis mutations have such small patient populations that clinical trial studies are not feasible," noted Janet Woodcock, MD, director of FDA's Center for Drug Evaluation and Research. "This challenge led us to using an alternative approach based on precision medicine, which made it possible to identify certain gene mutations that are likely to respond to Kalydeco." Ivacaftor is indicated for patients aged 2 years and older who have one mutation in the CFTR gene that is responsive to drug treatment based on clinical and/or in vitro (lab) data. The expanded indication will affect another 3% of people with cystic fibrosis. Ivacaftor, available as tablets or oral granules taken 2 times a day with fat-containing food, helps the protein made by the CFTR gene function better and thus improves lung function and other aspects of cystic fibrosis. Common adverse effects of ivacaftor include headache; upper respiratory tract infection (common cold) including sore throat, nasal or sinus congestion, or runny nose; stomach pain; diarrhea; rash; nausea; and dizziness. The drug is associated with risks such as elevated transaminases and pediatric cataracts. Additionally, coadministration with strong CYP3A inducers substantially reduces exposure of ivacaftor, which may reduce effectiveness, and is thus not recommended.