Long-term safety and efficacy of ivacaftor in patients with cystic fibrosis who have the Gly551Asp-CFTR mutation: a phase 3, open-label extension study (PERSIST)

Background: Ivacaftor, a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator, is approved for the treatment of patients with cystic fibrosis aged 6 years or older with Gly551Asp-CFTR. We assessed the safety and efficacy of ivacaftor during 96 weeks of PERSIST in patients with cystic fibrosis who completed a previous 48-week, placebo-controlled trial of the drug (STRIVE or ENVISION).

Methods: In this phase 3, open-label extension study, patients received ivacaftor 150 mg every 12 h in addition to their prescribed cystic fibrosis therapies. Patients who received placebo in their previous study initiated ivacaftor in this extension study. Patients were eligible if they had a Gly551Asp-CFTR mutation on at least one allele. The primary objective was to assess the long-term safety profile of ivacaftor as assessed by adverse events, clinical laboratory assessments, electrocardiograms, vital signs, and physical examination; secondary measures included change in forced expiratory volume in one second (FEV1), weight, and pulmonary exacerbations. This study is registered with ClinicalTrials.gov, number NCT01117012 and EudraCT, number 2009-012997-11.

Findings: Between July 8, 2010, and April 8, 2013, 144 adolescents/adults (≥12 years) from STRIVE and 48 children (6-11 years) from ENVISION were enrolled. Across both trials, 38 (20%) patients had a serious adverse event during the first 48 weeks and 44 (23%) during the subsequent 48 weeks. Two adults (1%) and one child (<1%) discontinued because of adverse events. The most common adverse events were pulmonary exacerbation, cough, and upper respiratory tract infection. Patients previously treated with ivacaftor had sustained improvements in FEV1, weight, and rate of pulmonary exacerbations for up to 144 weeks of treatment. Among adolescents/adults and children who previously received ivacaftor, absolute change in FEV1 at week 96 (144 weeks ivacaftor) was 9·4 and 10·3 % points and absolute increase in weight was 4·1 kg and 14·8 kg, respectively. For adolescents/adults only, the pulmonary exacerbation rate remained suppressed compared with that of patients who received placebo in the placebo-controlled study.

Interpretation: At 144 weeks of treatment, ivacaftor was well tolerated, with no new safety concerns. Ivacaftor also provided durable effects for 144 weeks in patients who had received active treatment in the placebo-controlled study. Those patients who previously received placebo had improvements comparable to those of patients treated with ivacaftor in the placebo-controlled study.

Funding: Vertex Pharmaceuticals Inc.