(397) Sinonasal epithelial functional and transcriptional responses to long-term highly effective CFTR corrector therapy

Background: The CF airway epithelium manifests detrimental structural and functional changes elicited by chronic inflammation and infection, which fuel cycles of injury and incomplete repair secondary to CFTR mutation. The CFTR modulators elexacaftor+tezacaftor+ivacaftor (ETI) improve pulmonary health in people with cystic fibrosis (PwCF). However, the extent to which underlying airway epithelial structural and functional defects are mitigated by long-term ETI treatment remains untested.

Methods: PwCF (with F508del/F508del or F508del/minimal function mutations) were enrolled and evaluated by sinus computed tomography (CT) and patient-reported outcome measures for changes in sinus disease and general health status at baseline and after 6 and 24 months of ETI. Sinonasal cells obtained at the same timepoints from the right nostril by brush biopsy were subjected to bulk whole-transcriptome sequencing (RNAseq). Cells from the left nostril were subjected to primary air-liquid interface (ALI) culture to assess cellular differentiation and epithelial barrier and mucociliary transport function. Single cell sequencing (scRNAseq) was performed on an additional 9 healthy controls and 10 PwCF who have been receiving ETI for 6-12 months.

Results: Thirty participants initially enrolled and completed baseline data collection. Clinical and transcriptomic analyses were previously completed for 25 and 23 participants respectively at the baseline vs. 6 month timepoints; and 23 will complete 24 month follow-up by 06/01/22. After 6 months of ETI, RNAseq revealed gene expression changes consistent with greatly reduced neutrophilic inflammation, which correlated with substantial clinical improvements in sinus disease. Genes related to ciliated cell formation and function showed more modest and variable increases. Consistent with transcriptomic changes, sinonasal ALI cultures had improved ciliated cell differentiation and barrier and mucociliary transport capacity at 6 months of ETI compared to baseline. However, scRNAseq revealed that the ETI-treated CF sinonasal epithelium remained abnormal compared to healthy controls. The CF sinonasal mucosa retained evidence of substantial neutrophilic inflammation, as well as signatures consistent with ciliated cell dysfunction and mucous and squamous metaplasia. Alterations in Wnt and other developmental signaling pathways correlated with persistent dysfunction of the CF airway epithelium despite ETI therapy. We will report transcriptomic changes and correlations with clinical outcomes for the 24-month timepoint.

Conclusions: These data demonstrate that ETI initiated in adults with existing airway disease reduced inflammation and improved structure and function in the CF sinonasal epithelium at 6 months; however, ETI did not restore the epithelium to healthy control status. We anticipate the effect will be sustained over 2 years of ETI therapy. Unraveling the molecular mechanisms driving these responses will have implications for the long-term use of highly effective CFTR corrector therapy in PwCF.

Acknowledgements: CFF grants TAYLOR19A0 and VLADAR18G0 and the Marshall and Margherite McComb Foundation.

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