Objectives: Aspergillus fumigatus is the commonest fungi to colonise the airways of people with cystic fibrosis (CF). Colonisation, both with or without the presence of allergic bronchopulmonary aspergillosis (AGPA), has been found to be associated with increased respiratory exacerbations, hospitalisations, reduced pulmonary function and CT scan abnormalities. Management with anti-fungal agents has shown limited clinical benefit, as well as issues with side effects and drug resistance. The effect of CFTR modulator therapies; revolutionary in the management of CF in recent years, on Aspergillus related disease in CF has yet to be established. We aimed to assess whether elexacaftor-tezacaftor-ivacaftor (ETI) therapy impacted on Asp. fumigatus serology in a population of adults with CF.