A Phase 3, Open-Label Study of Lumacaftor/Ivacaftor in Children 1 to Less Than 2 Years of Age with Cystic Fibrosis Homozygous for <i>F508del-CFTR</i>.

Abstract

<b>Rationale:</b> Previous phase 3 trials showed that treatment with lumacaftor/ivacaftor was safe and efficacious in people aged ⩾2 years with cystic fibrosis (CF) homozygous for the <i>F508del</i> mutation in <i>CFTR</i> (CF transmembrane conductance regulator) (<i>F</i>/<i>F</i> genotype). <b>Objectives:</b> To assess the safety, pharmacokinetics, and pharmacodynamics of lumacaftor/ivacaftor in children aged 1 to <2 years with the <i>F</i>/<i>F</i> genotype. <b>Methods:</b> This open-label, phase 3 study consisted of two parts (part A [<i>n</i> = 14] and part B [<i>n</i> = 46]) in which two cohorts were enrolled on the basis of age (cohort 1, 18 to <24 mo; cohort 2, 12 to <18 mo). For the 15-day treatment period in part A, the lumacaftor/ivacaftor dose was based on weight at screening. Pharmacokinetic data from part A were used to determine dose-based weight boundaries for part B (24-wk treatment period). <b>Measurements and Main Results:</b> The primary endpoint of part A was pharmacokinetics, and the primary endpoint for part B was safety and tolerability. Secondary endpoints for part B were absolute change in sweat chloride concentration from baseline at Week 24 and pharmacokinetics. Analysis of pharmacokinetic data from part A confirmed the appropriateness of part B dosing. In part B, 44 children (95.7%) had adverse events, which for most were either mild (52.2% of children) or moderate (39.1% of children) in severity. The most common adverse events were cough, infective pulmonary exacerbation of CF, pyrexia, and vomiting. At Week 24, mean absolute change from baseline in sweat chloride concentration was -29.1 mmol/L (95% confidence interval, -34.8 to -23.4 mmol/L). Growth parameters (body mass index, weight, length, and associated <i>z</i>-scores) were normal at baseline and remained normal during the 24-week treatment period. Improving trends in some biomarkers of pancreatic function and intestinal inflammation, such as fecal elastase-1, serum immunoreactive trypsinogen, and fecal calprotectin, were observed. <b>Conclusions:</b> Lumacaftor/ivacaftor was generally safe and well tolerated in children aged 1 to <2 years with the <i>F</i>/<i>F</i> genotype, with a pharmacokinetic profile consistent with studies in older children. Efficacy results, including robust reductions in sweat chloride concentration, suggest the potential for CF disease modification with lumacaftor/ivacaftor treatment. These results support the use of lumacaftor/ivacaftor in this population. Clinical trial registered with www.clinicaltrials.gov (NCT03601637).