Effectiveness of lumacaftor/ivacaftor initiation in children with cystic fibrosis aged 2 through 5 years on disease progression: Interim results from an ongoing registry-based study

•Children who initiated LUM/IVA treatment between 2 and 5 years of age in real-world settings had:○Increases in BMI, height, and weight percentiles relative to modulator-naïve comparators.○Reductions in pulmonary exacerbations and hospitalizations relative to baseline.•Data suggest early initiation of LUM/IVA could have a beneficial impact on CF disease progression. Lumacaftor/ivacaftor (LUM/IVA) has been shown to be safe and efficacious in people with cystic fibrosis (CF) ≥1 year of age. To assess the impact of early LUM/IVA initiation on CF disease progression, a 6-year observational study leveraging data from existing CF patient registries is being conducted in children with CF homozygous for F508del (F/F genotype) who were aged 2 through 5 years at treatment initiation. Here we present interim results from this study focusing on data from the European CF Society Patient Registry (ECFSPR). The LUM/IVA cohort included children in the ECFSPR who started LUM/IVA between 15 January 2019 and 31 December 2020. Longitudinal trends in growth parameters, pulmonary exacerbations, hospitalizations, safety outcomes, and other effectiveness outcomes in the LUM/IVA cohort were compared to those in two modulator-naïve cohorts: (i) matched concurrent cohort heterozygous for F508del and a minimal function mutation (F/MF concurrent comparator cohort) and (ii) matched concurrent cohort with the F/F genotype from countries without commercial access to LUM/IVA as of 2020 (F/F concurrent comparator cohort). The LUM/IVA cohort matched to the F/MF concurrent comparator cohort had 681 children and the LUM/IVA cohort matched to the F/F concurrent comparator cohort had 183 children. LUM/IVA cohorts had increases in body mass index percentiles relative to the matched F/MF and F/F concurrent comparator cohorts (mean difference in change from baseline: 8.4 [95% CI: 5.5, 11.3] and 11.8 [95% CI: 5.9, 17.7], respectively). Increases in height and weight percentiles were also observed in the LUM/IVA cohort relative to the F/MF and F/F concurrent comparator cohorts. Reductions in pulmonary exacerbations and hospitalizations relative to baseline and the F/F concurrent comparator cohort were seen in 2021. This interim analysis showed favorable trends in clinical outcomes, including growth parameters, pulmonary exacerbations, and hospitalizations, suggesting an early beneficial effect of LUM/IVA treatment in children aged 2 through 5 years at treatment initiation.