Long-Term Ivacaftor in People Aged 6 Years and Older with Cystic Fibrosis with Ivacaftor-Responsive Mutations

Introduction: Mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR) affect the quantity and/or function of CFTR protein reaching the cell surface. Ivacaftor, a CFTR potentiator that enhances chloride transport, increases the channel-open probability of normal and dysfunctional CFTR. Initially approved for people with CF (pwCF) with G551D-CFTR gating mutations, ivacaftor demonstrated clinical benefit in pwCF with other gating mutations and certain residual function mutations, including R117H-CFTR, in clinical studies. We evaluated the long-term safety and efficacy of ivacaftor in pwCF aged 6 years and older with non-G551D-CFTR ivacaftor-responsive mutations.

Methods: Efficacy and safety data from a phase 3, multicenter, open-label, extension study for participants from Study 110 (R117H-CFTR mutations), Study 111 (non-G551D-CFTR gating mutations), and Study 113 (n-of-1 pilot study in participants with residual CFTR function) were analyzed. Following washout from the randomized parent study, participants received oral ivacaftor 150 mg once every 12 h for 104 weeks.

Results: Forty-one of 121 participants completed treatment through 104 weeks; 59 participants who did not complete the extension study continued treatment with commercial ivacaftor. The most common adverse events were pulmonary exacerbation (46.3%) and cough (33.9%). Most treatment-emergent adverse events were mild/moderate in severity and consistent with manifestations of CF or the ivacaftor safety profile. Rapid, durable improvement occurred across all efficacy endpoints.

Conclusions: Ivacaftor was generally safe and well tolerated with no new safety concerns for up to 104 weeks in pwCF with ivacaftor-responsive mutations. The pattern of improvement across efficacy endpoints was durable and generally consistent with parent-study outcomes.

Trial Registration: NCT01707290.