Drug repurposing for Cystic Fibrosis: identification of drugs that induce CFTR-independent fluid secretion in nasal organoids

Individuals with Cystic Fibrosis (CF) suffer from severe respiratory disease due to a genetic defect in the Cystic Fibrosis Transmembrane conductance Regulator ( CFTR ) gene, which impairs airway epithelial ion and fluid secretion. New CFTR modulators that restore mutant CFTR function have been recently approved for a large group of people with CF (pwCF), but ∼19% of pwCF cannot benefit from CFTR modulators [1]. Restoration of epithelial fluid secretion through non-CFTR pathways might be an effective treatment for all pwCF. Here we developed a medium-throughput 384-wells screening assay using nasal CF airway epithelial organoids, with the aim to repurpose FDA-approved drugs as modulators of non-CFTR dependent epithelial fluid secretion. From a ∼1400 FDA-approved drug library, we identified and validated 12 FDA-approved drugs that induced CFTR-independent fluid secretion. Among the hits were several cAMP-mediating drugs, including β2-adrenergic agonists. The hits displayed no effects on chloride conductance measured in Ussing chamber, and fluid secretion was not affected by TMEM16A as demonstrated by knockout (KO) experiments in primary nasal epithelial cells. Altogether, our results demonstrate the use of primary nasal airway cells for mediumscale drug screening, target validation with a highly efficient protocol for generating CRISPR-Cas9 KO cells and identification of compounds which induce fluid secretion in a CFTR- and TMEM16A-indepent manner.