Changes in exercise capacity in people with Cystic Fibrosis after one year of Elexacaftor/Tezacaftor/Ivacaftor treatment – A Danish prospective cohort

•The impact of ETI treatment on exercise capacity measured by CPET in people with cystic fibrosis.•A prospective design and the inclusion of a considerable Danish cohort.•An increase in oxygen uptake among pwCF after one year of ETI treatment without any further intervention.•A significant outcome but it seems not to be clinically relevant. Cystic Fibrosis (CF) is an inherited multiorgan disease that causes lung damage and early death. People with CF (pwCF) experience diminished exercise capacity compared to the general population. This is due to an accelerated decline in lung function resulting from recurrent lung infections, declining lung function and nutritional challenges. Since 2020 the CFTR-modulator Elexacaftor/Tezacaftor/Ivacaftor (ETI) has been approved for pwCF aged 12 and above in Denmark. Initial experiences with the medication have shown promising results, including improved lung function and disease stability. To date a limited number of studies have evaluated the impact of CFTR-modulators on exercise capacity in pwCF. The study aims to assess the impact of one year of ETI treatment, without any further intervention, on exercise capacity measured through cardiopulmonary exercise test (CPET) in pwCF aged 12 years and above. A Danish prospective registry cohort study including pwCF from CF-Center Copenhagen, Copenhagen University Hospital and CF-Center Aarhus, Aarhus University Hospital. Participants underwent CPET before initiating ETI and at follow up one year later. Primary outcomes were VO₂ peak (ml/kg/min), secondary outcomes were VO2 peak (ml/min), VO2 peak (% pred), watt-max, HR-max and saturation at max. The difference between baseline and follow-up was assessed using a paired-sample t-test and regression analyses were applied to relevant outcomes. We included 229 pwCF in the analyses. An increase in oxygen uptake, VO₂ peak (ml/kg/min) from baseline to follow-up was observed; 0.6, 95% CI [0.06; 1.09] p = 0.03. Moreover, significant increase was noted for all other CPET outcomes. Regression analysis showed that changes in FEV₁% pred and BMI could explain some of the differences, 0.05 ml/kg/min, 95% CI [0.01, 0.1] p = 0.02 and -0.5 ml/kg/min, 95% CI [-0.8, -0.2] p = 0.002 respectively. Among Danish pwCF we found a significant, but not clinically relevant, increase in oxygen uptake, after one year of ETI treatment.