Reported Adverse Events in Patients with CF Receiving Treatment with Elexacaftor/Tezacaftor/Ivacaftor: 5 Years Observational Study

<b>Background:</b> Elexacaftor/tezacaftor/ivacaftor (ETI) treatment is showing remarkable beneficial effects in people with Cystic Fibrosis (pwCF) harboring the F508del mutation in the Cystic Fibrosis Transmembrane conductance Regulator (<i>CFTR</i>) gene. Although this therapy is generally well tolerated in pwCF, some adverse events (AEs) have been recently described both in controlled studies and in post-marketing observations. <b>Methods</b>: We followed 414 pwCF carrying F508del <i>CFTR</i> that initiated ETI treatment, recording AEs for a period of 5 years. <b>Results</b>: A total of 142 AEs were reported. The most frequent AEs in the whole cohort were liver marker elevation, skin rush, epigastric pain, headache, and depression. Considering pediatric subjects, psychiatric and gastrointestinal disorders were the most frequent AEs. Only one patient reported a severe AE, leading to treatment discontinuation. In case of AEs, different decisions on ETI treatment were made, including temporary interruption and temporary or permanent dosage modification. <b>Conclusions</b>: Throughout the long-term observational period, almost 21% of pwCF experienced at least one AE. Psychiatric disorders, in particular attention deficit, were the most prevalent issue in our pediatric cohort, whereas adult patients mainly reported depression, anxiety and sleep disorders. This study therefore strengthen the recommendation of screening for changes in mental health during ETI treatment. AEs led to the permanent reduction of ETI dosage in 32% of cases, raising the issue of safety in relation to dosage reduction, efficacy, and minimum ETI levels. Eventually, this study highlights the need for a longitudinal monitoring of ETI safety since a significant number of AEs occurred after one year of treatment.