Background and Importance Elexacaftor/tezacaftor/ivacaftor (ETI) are bringing about a major change in the treatment of cystic fibrosis (CF) patients. However, continuing with other treatments such as nebulised antibiotics is necessary.

Aim and Objectives To assess the adherence to inhaled antibiotics before and after starting ETI. Secondary objectives: To assess effectiveness of ETI.

Material and Methods Observational, retrospective study carried out between March 2023 and September 2023, including patients who started with ETI before September 2022, 12 years of age or older when they started, and treated with at least one nebulised antibiotic.

Variables: age, sex, change from baseline in percentage of predicted forced expiratory volume in 1 second (FEV1) at month 12, difference in rate of pulmonary exacerbations 1 year before and after starting ETI, difference in Medication Possession Ratio (MPR) to nebulised antibiotics 1 year before and after starting ETI and MPR to ETI for 12 months.

Data were collected from electronic medical records and pharmacy dispensing programs.

A statistical analysis was performed using dependent samples t-test with IBM SPSS Statistics v21.0.

The study was approved by Ethics Committee of the hospital.

Results In total, 33 patients were included, 21/33 (63.6%) were female. The mean age was 28.1 (±12.5). 14/33 (42.4%) patients had been previously treated with tezacaftor/ivacaftor.

Percentage of predicted FEV1 was 17.8% higher (95% CI 11.8–23.7) at 12 months. Rate of pulmonary exacerbations was 70.2% lower (95% CI 43.3–97.2) and rate of severe pulmonary exacerbations was 86.1% lower (95% CI 43,2–128,9) 12 months after starting ETI. MPR to nebulised antibiotics was 22% lower (95% IC 7,5–36,5) 12 months after starting ETI. (P<0,001 for all comparisons). MPR to ETI was 89,7% (±18,5).

Conclusion and Relevance The introduction of ETI to CF treatment has been a hopeful advance. ETI has shown a good efficacy in our population. However, the adherence to nebulised antibiotics decreased significantly. More studies are needed to evaluate the safety of withdrawing nebulised therapies post-ETI. A strategy to improve adherence in patients with CF has been initiated in collaboration with the CF unit of our hospital.

References and/or Acknowledgements 1. Song JT, et al. Research letter: The impact of elexacaftor/tezacaftor/ivacaftor on adherence to nebulised maintenance therapies in people with cystic fibrosis. J Cyst Fibros 2022;21:1080–1

Conflict of Interest No conflict of interest.