• Venkateshwar Mutyam, Ming Du, Xiaojiao Xue, Kim M Keeling, E Lucile White, J Robert Bostwick, Lynn Rasmussen, Bo Liu, Marina Mazur, Jeong S Hong, Emily Falk Libby, Feng Liang, Haibo Shang, Martin Mense, Mark J Suto, David M Bedwell, and Steven M Rowe.
• 1 Department of Medicine.
• Am. J. Respir. Crit. Care Med. 2016 Nov 1; 194 (9): 109211031092-1103.

RationalePremature termination codons (PTCs) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF). Several agents are known to suppress PTCs but are poorly efficacious or toxic.ObjectivesTo determine whether there are clinically available agents that elicit translational readthrough and improve CFTR function sufficient to confer therapeutic benefit to patients with CF with PTCs.MethodsTwo independent screens, firefly luciferase and CFTR-mediated transepithelial chloride conductance assay, were performed on a library of 1,600 clinically approved compounds using fisher rat thyroid cells stably transfected with stop codons. Select agents were further evaluated using secondary screening assays including short circuit current analysis on primary cells from patients with CF. In addition, the effect of CFTR modulators (ivacaftor) was tested in combination with the most efficacious agents.Measurements And Main ResultsFrom the primary screen, 48 agents were selected as potentially active. Following confirmatory tests in the transepithelial chloride conductance assay and prioritizing agents based on favorable pharmacologic properties, eight agents were advanced for secondary screening. Ivacaftor significantly increased short circuit current following forskolin stimulation in cells treated with pyranoradine tetraphosphate, potassium p-aminobenzoate, and escin as compared with vehicle control. Escin, an herbal agent, consistently induced readthrough activity as demonstrated by enhanced CFTR expression and function in vitro.ConclusionsClinically approved drugs identified as potential readthrough agents, in combination with ivacaftor, may induce nonsense suppression to restore therapeutic levels of CFTR function. One or more agents may be suitable to advance to human testing.

26 keywords...

hide…