The approval triples the number of rare gene mutations that ivacaftor can now treat.
The FDA expanded the use of ivacaftor (Kalydeco) to treat additional mutations of cystic fibrosis from 10 mutations to 33.
The expanded indication was based in part on the results of laboratory testing used in conjunction with results from earlier human clinical trials, according to a press release.
Findings from an in vitro cell-based model system demonstrated the ability to reasonably predict clinical response to ivacaftor. In the laboratory test, the investigators found that additional mutations responded to ivacaftor.
This allowed them to extrapolate the clinical benefit that was demonstrated in earlier clinical trials of other drugs, and resulted in the addition of gene mutations that the drug is now indicated for, according to the release.
“Many rare cystic fibrosis mutations have such small patient populations that clinical trial studies are not feasible,” Janet Woodcock, MD, director of the FDA’s Center for Drug Evaluation and Research, said in the release. “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 comes in the form of tablets or oral granules, and should be taken twice-daily with fat-containing food. It is designed to improve the function of the protein made by the CFTR gene, resulting in an improvement in lung function and other aspects of cystic fibrosis, including weight gain.
“If the patient’s genotype is unknown, an FDA-cleared cystic fibrosis mutation test should be used to detect the presence of a CFTR mutation followed by verification with bi-directional sequencing when recommended by the mutation test instructions for use,” the release stated.
The most common adverse events of ivacaftor included headache; upper respiratory tract infection, including sore throat, nasal or sinus congestion, or runny nose; abdominal pain; diarrhea; rash; nausea; and dizziness.
Ivacaftor is associated with risks that include elevated transaminases and pediatric cataracts. Co-administration with strong CYP2A inducers, such as rifampin, substantially decreases exposure of ivacaftor, and as a result, may diminish efficacy, therefore, it is not recommended.