528 Linking CFTR modulators to opportunistic bacterial infections in cystic fibrosis

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators improve clinical outcomes with variable efficacy in patients with cystic fibrosis (CF). However, changes produced by bacterial persistence and adaptation in addition to antibiotic regimens could influence CFTR modulator efficacy and vice versa and hence clinical outcomes. We first evaluated the effects of ivacaftor (IVA), lumacaftor (LUM), tezacaftor, elexacaftor and elexacaftor/tezacaftor/ivacaftor (ETI), alone or combined with antibiotics, on sequential Staphylococcus aureus and Pseudomonas aeruginosa CF isolates. IVA and ETI showed the most potent direct antimicrobial activity against S. aureus , while P. aeruginosa was not affected. Additive effects or synergies were observed between the CFTR modulators and antibiotics against both S. aureus and P. aeruginosa , independently of the stage of colonization. IVA and LUM were the most effective in potentiating antibiotic activity against S. aureus , while IVA and ETI enhanced mainly polymyxins activity against P. aeruginosa . Next, we evaluated the effect of P. aeruginosa pneumonia on the pharmacokinetics of IVA in mice. The time-concentration curves of IVA and its metabolites in plasma, lung and epithelial lining fluid were influenced by P. aeruginosa infection. The area under the concentration-time curve showed that airway exposure to IVA was greater in infected than non-infected mice. These results suggest that CFTR modulators can have direct antimicrobial properties and/or enhance antibiotic activity against S. aureus and P. aeruginosa . Furthermore, bacterial infection impacts the IVA concentration and airway exposure, potentially affecting its efficacy. Our findings suggest optimizing host- and pathogen-directed drug regimens to improve efficacy for personalized treatment. ### Competing Interest Statement The authors have declared no competing interest.