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A7625 - hCFTR (human Cystic Fibrosis Transmembrane Conductance Regulator) mRNA Delivered Using a Novel Biodegradable Nanovector to CFTR Knock-Out Rats Improves CFTR Expression and Chloride Transport Across the Nasal Epithelium In Vivo
Author Block: N. Kaza1, L. Tang1, R. Shei1, D. Stanford1, L. W. Rasmussen1, F. DeRosa2, S. Karve2, M. Heartlein2, S. M. Rowe1; 1Medicine, Div of Pulmonary, Allergy and Critical Care, University of Alabama at Birmingham, Birmingham, AL, United States, 2Translate Bio, Cambridge, MA, United States.
RATIONALE: Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene resulting in dysfunction of the CFTR protein, an anion channel. Restoring normal CFTR function across the airway epithelium can help alleviate the respiratory symptoms of CF disease. Here, we investigate the efficacy of delivering a codon-optimized human CFTR (hCFTR) mRNA via a novel biodegradable nanovector in CFTR knockout rats (CFTR-/-), an investigational approach in humans. METHODS: Adult CFTR-/- rats were treated with 7 doses (QOD) of 200µL biodegradable nanovector solution, delivered by either oropharyngeal aspiration (N=7) or whole-body exposure (N=5), containing either hCFTR mRNA (concentration of 2mg/mL; N=7) or no mRNA vehicle control (N=5). Physiologic ion transport across the nasal respiratory epithelium was assessed in vivo by nasal potential difference (NPD) measurements, 24 hrs post dosing. The expression of hCFTR in CFTR-/- rat lungs was assessed by histochemistry. RESULTS: Total CFTR-dependent Cl¯ transport by NPD (ΔCl¯ free + forskolin) was significantly improved in hCFTR-treated rats (ΔPD= -4.4±1.4 mV, p=0.01) whereas vehicle controls were consistent with CF (+1.7±1.3 mV). ΔPD components ΔCl¯ free (-1.3±1.0 mV hCFTR vs. +1.0±1.1 mV vehicle) and Δforskolin (-2.6±0.8 mV hCFTR vs. +0.8±1.2 mV vehicle, p=0.04) exhibited similar trends. Both delivery methods exhibited very similar results on NPD, and the magnitude of effect is ~ 40% of wild type CFTR function. hCFTR protein expression was confirmed in the peripheral airways and lung parenchyma of CFTR-/- rats by robust immunohistochemical staining in hCFTR treated rats, but not observed in vehicle controls. Of note, a cohort of wild type rats also demonstrated an increase in ΔPD (-16.5±1.2 mV hCFTR vs. -11.5±1.8 vehicle) and was without adverse effects. Additional studies are in progress to characterize effects on ion transport in the lower airways (i.e. excised trachea and bronchus short-circuit current) in CF rats. CONCLUSIONS: hCFTR mRNA replacement therapy in CFTR-/- rats using a novel nanovector delivery system significantly improved CFTR-dependent Cl¯ transport by nasal transepithelial potential difference and resulted in diffuse CFTR staining throughout the lower (distal) airways and parenchyma. Further studies are ongoing to assess the functional effect of hCFTR replacement on airway surface liquid (ASL), periciliary layer (PCL), ciliary beat frequency (CBF), and mucociliary transport (MCT) using micro-optical coherence tomography (µOCT) in the airways of CFTR-/- rats, with and without the presence of chronic P. aeruginosa infection.