(154) In Vitro Responses OF F508DEL Human Nasal Epithelial Cells Correlate to Clinical Improvement to ELEXACAFTOR/TEZACAFTOR/IVACAFTOR

Background: Well-differentiated human airway epithelial (HAE) cells have formed an important basis for preclinical evaluation of CFTR modulators. Advances for expansion of cells have been leveraged through multi-site collections of human nasal epithelial (HNE) cells through CF Foundation TDN-sponsored observational studies. Our lab has previously demonstrated that in vitro effects of ivacaftor in G551D HNE (specifically CFTR function and airway surface liquid (ASL) or mucociliary transport rate (MCT)) correlated with clinical improvements in sweat chloride and lung function (ppFEV₁), respectively, in the same patients in response to ivacaftor during the GOAL study. This study aimed to determine whether HNE cells derived from patients respond to elexacaftor/tezacaftor/ivacaftor (ETI) and whether the functional responses correlate to clinical improvement with newly initiated ETI on a groupwise and individual basis in the PROMISE study.

Methods: HNE Cells were collected from donors participating in the PROMISE study and were expanded using conditional reprogramming. Cells were differentiated at air-liquid interface using Ultroser-G supplemented differentiation media for 21-28 days. Inserts were analyzed for forskolin-stimulated CFTR-dependent current (Isc) using modified Ussing chambers after pre-treatment with elexacaftor (3μM) /tezacaftor (3μM) and ivacaftor (acute treatment, 10μM) followed by CFTR Inh-172 (20 μM). In addition, each donor was analyzed for change in mucociliary transport (MCT) rate, airway surface liquid depth (ASL), and ciliary beat frequency (CBF) using micro-optical coherence tomography after chronic (48-hour treatment of ETI).

Results: Differentiated monolayers from 19 donors (10 F508del/F508del, 9 F508del/minimal function) have been analyzed to date. Monolayers demonstrated a mean ETI-treated, forskolin-stimulated Iscof 7.6±3.0 μA/cm² (vs 2.1±2.0 μA/cm² for vehicle, p< 0.0001, representing 48% restoration of WT-CFTR Isc). CFTR inhibition with CFTR Inh-172 mirrored these responses. Monolayers demonstrated improved ASL (11.9±4.9 μm ETI vs 5.3±2.5 μm vehicle control, p< 0.05, a 56% improvement with ETI vs vehicle normalized to baseline measurements); acquisition of MCT and CBF data was limited due to variable degrees of differentiation. On an individual basis, ETI-treated Fsk-stimulated Isc correlated with augmented ASL with ETI treatment (r=0.74, p< 0.001). ETI-treated Isc also moderately correlated to 6-month post-ETI sweat chloride (r = 0.59, p< 0.05), but did not relate to absolute change in ppFEV₁ (r = 0.26, p=NS) in this preliminary analysis. Increases in ASL correlated with improvements in ppFEV₁after 6 months of treatment (r=0.58, p < 0.05) Stratification based on prior modulator status is in progress.

Conclusions: Results from the PROMISE HNE sub study demonstrate that HNE cells derived from participants in a multi-center study recapitulate expected changes in CFTR activity and airway surface liquid depth, including the treatment effects of ETI CFTR modulator treatment. At interim analysis, changes in Isc correlated with sweat chloride, and ASL depth correlated to clinical response (ppFEV₁), consistent with relationships established in ivacaftor treated HNE in the GOAL study. These findings add additional confidence that HNE cells are an important in vitro biomarker to better understand treatment response to CFTR-directed therapies, including individual level responses. Supported by CFF and NIH.

Acknowledgements: on behalf of the PROMISE Investigators.

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