P042 Nasal nitric oxide increases in patients with cystic fibrosis treated with elexacaftor/tezacaftor/ivacaftor

Objectives: In health, nitric oxide (NO) can be measured in high concentrations in the upper respiratory tract. It has been shown that nasal NO (nNO) is significantly lower in patients with sinonasal inflammation such as patients with Cystic Fibrosis (CF). In patients with CF treated with elexacaftor-tezacaftor-ivacaftor (ETI), clinical improvement of sinonasal inflammatory symptoms could be observed. We therefore hypothesised that nNO would increase in patients undergoing ETI treatment between a baseline measurement and after several months of treatment. Furthermore we are interested to see if nNO correlates with other parameters such as inflammatory markers, lung function and sweat chloride. Methods: 32 patients with CF had nNO measurement at baseline before starting ETI treatment and repeated the measurement after ten to twelve months of treatment. NNO was measured using velum closure (VC) techniques in cooperative patients and tidal breathing (TB) for all patients. Preliminary data analyses were conducted for thirteen patients with paired measurements. Results: At baseline and under ETI therapy, nNO had a mean value of 521.60 (standard deviation (SD): 204.21) ppb and 863.81 (SD: 230.45) ppb respectively for VC (p < 0.001). For TB measurement, the mean value at baseline and under ETI therapy was 313.54 (SD: 122.88) ppb and 519.70 (SD: 185.45) ppb respectively (p < 0.001). Analysis of nNO of all patients and correlation analysis for inflammatory markers from nasal lavages, lung function testing and sweat chloride is ongoing, but will be finalized until June 2023. Conclusions: In patients with CF undergoing ETI treatment, the nNO value significantly increased after several months of treatment in comparison to baseline. This suggests that nNO is a potential non-invasive biomarker to examine sinonasal inflammatory disease and supports the observation of clinical improvement in these patients.