Long-term impact of elexacaftor/tezacaftor/ivacaftor on small and large airways in pwCF aged \(\geq\) 6 years

\(\bf Background\) While studies have consistently reported improvements in lung function during elexacaftor/tezacaftor/ivacaftor (ETI) therapy for people with cystic fibrosis (pwCF), individual response predictors remain poorly understood, and there is limited real-world data relating to children aged 6–11 years. \(\bf Methods\) Lung function data from the German CF registry 2020–24 were analysed before and up to 24 months after ETI therapy initiation in adults, adolescents and children aged ≥6 years. Data were stratified for percent predicted forced expiratory volume in 1 s (ppFEV1) increase during therapy (<5% versus >5%), underlying mutation, and pretreatment disease severity. \(\bf Findings\) Data from 2375 pwCF were analysed. After starting ETI, ppFEV1 increased most in adolescents with baseline ppFEV1 >40–60% (median increase 16.8–20.2%); the corresponding increase in adults with the same initial lung function was 11.2–11.5%. After an initial increase, ppFEV1 remained stable for 24 months in all age groups. No predictors for greater improvement (>5% ppFEV1 gain) were identified but pwCF with normal ppFEV1 before ETI therapy had smaller increases during treatment. Forced mid-expiratory flow (FEF25–75) increased to a similar extent in children and adolescents (+13%) and adults (+9.5%). \(\bf Interpretation\) Our real-world data showed significant improvements in lung function, including large and small airways, during 24 months’ ETI therapy in pwCF aged ≥6 years. Notable improvements, particularly in small airways, were observed even in children and adolescents with normal ppFEV1 before ETI. These findings underscore the importance of early ETI therapy initiation to prevent irreversible lung damage.