This guidance represents the Food and Drug Administration's (FDA's) current thinking on this topic. It does not create or confer any rights for or on any person and does not operate to bind FDA or the public. You can use an alternative approach if the approach satisfies the requirements of the applicable statutes and regulations. If you want to discuss an alternative approach, contact the FDA staff responsible for implementing this guidance. If you cannot identify the appropriate FDA staff, call the appropriate number listed on the title page of this guidance.I.

No abstract

On May 17, 2017, the U.S. Food and Drug Administration expanded the patient population for use of ivacaftor to include patients with cystic fibrosis with relatively rare mutations in the cystic fibrosis transmembrane conductance regulator gene. The label expansion is unique in that clinical efficacy was not based on clinical data but on in vitro assay data demonstrating increased chloride ion transport across cells in response to ivacaftor. Such an approach provides a pathway for adding difficult-to-study mutation-based cystic fibrosis subpopulations to the indication as well as defining mutations unresponsive to ivacaftor and has important implications for cystic fibrosis drug development and other rare genetic diseases whose genetics and disease pathophysiology are well understood.

No abstract