The FDA has expanded the approved use of Kalydeco (ivacaftor) for treating cystic fibrosis. According to an agency press release, the approval triples the number of rare gene mutations that the drug can now treat, expanding the indication from the treatment of 10 mutations, to 33.
The agency based its decision, in part, on the results of laboratory testing, which it used in conjunction with evidence from earlier human clinical trials. The approach provides a pathway for adding additional, rare mutations of the disease, based on laboratory data.
“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.
Results from an in vitro cell-based model system have been shown to reasonably predict clinical response to Kalydeco. When additional mutations responded to Kalydeco in the laboratory test, researchers were thus able to extrapolate clinical benefit demonstrated in earlier clinical trials of other mutations. This resulted in the addition of gene mutations for which the drug is now indicated.
Kalydeco, available as tablets or oral granules taken two times a day with fat-containing food, helps the protein made by the CFTR gene function better and as a result, improves 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 expanded indication will affect another 3% of the cystic fibrosis population, impacting approximately 900 patients. Kalydeco serves as an example of how successful patient-focused drug development can provide greater understanding about a disease. For example, the Cystic Fibrosis Foundation maintains a 28,000-patient registry, including genetic data, which it makes available for research.
