FDA Expands Use of Cystic Fibrosis Drug

Yesterday, the FDA expanded the indication of ivacaftor (Kalydeco) for the treatment of additional mutations of cystic fibrosis. The approval expanded the indication from the treatment of 10 gene mutations to 33, more than tripling the amount of mutations the drug can treat, according to a press release.

The new approval is based on the results of laboratory testing and findings from earlier clinical trials. The FDA stated that this approval pathway allows for additional gene mutations of cystic fibrosis to be included in the indication.

Cystic fibrosis affects cells that produce mucus, sweat, and digestive juice, which are normally slippery as a result of the movement of chloride and water in and out of cells, according to the FDA. Patients with the condition have a mutated cystic fibrosis transmembrane conductance regulator (CFTR) gene that causes the secreted fluids to become thick and sticky.

These fluids build up in the body, which can lead to serious respiratory and digestive issues. This can also cause infections, diabetes, and other complications.

Findings from an in vitro cell model have been used to predict clinical response to ivacaftor. Investigators found that additional mutations responded to the model of the drug. This finding suggests that patients with these mutations would gain clinical benefits from treatment with ivacaftor, according to the release.

Ivacaftor is sold as tablets or oral granules indicated to be administered with fat-containing food. The drug helps a protein produced by the CFTR gene function optimally and improves symptoms of cystic fibrosis.

If a patient’s genotype is unknown, the FDA advises using an approved test to determine the CFTR mutation, which should then be followed by verification with bi-directional sequencing if recommended by the test instructions.

Ivacaftor is indicated for the treatment of patients aged 2 and older with a mutation in the CFTR gene. The expanded indication will expand treatment options for another 3% of the 30,000 patients with cystic fibrosis, including an additional 900 patients.

Common side effects of ivacaftor include headache, upper respiratory tract infection, stomach pain, diarrhea, rash, nausea, and dizziness. Ivacaftor has also been overserved to increase the risk for elevated transaminases and pediatric cataracts, according to the release.

The FDA warns that co-administration with strong CYP3A inducers, such as rifampin or St John’s wort, decreases exposure of ivacaftor, which may reduce efficacy. The FDA does not recommend taking the drugs together.

“Many rare cystic fibrosis mutations have such small patient populations that clinical trial studies are not feasible,” said Janet Woodcock, MD, director of the 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.”