A small molecule neutrophil elastase inhibitor, KRP-109, inhibits cystic fibrosis mucin degradation

Abstract Background Neutrophil elastase (NE) rapidly degrades gel-forming airway mucins in cystic fibrosis (CF) sputum. We hypothesized that KRP-109, a small molecule NE inhibitor, would inhibit CF mucin degradation in vitro. Methods Sputa were collected from CF patients ( n = 5) chronically or intermittently infected with Pseudomonas aeruginosa (P.a.). Mucin degradation was analyzed using western blot. Protease inhibitor studies were performed using alpha1-proteinase inhibitor (A1-PI Prolastin®) and KRP-109. Elastase activity assays were performed using spectrophotometry. Results There were significant differences in the amount of active NE in different CF sputum samples. KRP-109 decreased the NE driven mucin degradation in vitro. Pseudomonas elastases appeared to blunt elastase inhibition by A1-PI or KRP-109. Conclusion Inhibitors of neutrophil and Pseudomonas -derived elastases might rescue mucus clearance and reverse airway obstruction in CF.