Introduction: In patients with cystic fibrosis (CF) who carry at least one F508del mutation, treatment with elexacaftor/tezacaftor/ivacaftor (ETI) significantly improves lung function, body mass index and quality of life; however, impacts on body composition have not been well studied.

Aim: Our aim was to investigate the efficacy of ETI  on body composition in CF patients with pre-existing advanced lung disease.

Methods: We performed a single-centre, retrospective, observational analysis of the effect of ETI on body composition in CF patients with advanced lung disease (FEV1<40%) who were on triple therapy for at least 6 months.

Results: 11 CF patients (6F, 5M) with FEV1<40% before ETI were included. Differences in BMI and body composition (BMI, FFM, FFMI and Phase angle) before and after at least six months of triple therapy were statistically significant (% change in mean; Wilcoxon p-values reported): BMI 12.2%, FFM 6.3%, FFMI 5.4%, Phase angle 7.23%  (p ??.001).

Conclusions: In this study, initiation of ETI in CF patients with pre-existing advanced lung disease was associated with statistically significant improvement in BMI and BIA after at least six months of therapy.