Project Summary Cystic fibrosis (CF) is one the most common life-shortening single gene defective disorders with over 70,000 cases worldwide. Mortality of CF patients has significantly decreased over the last decades and we are facing new treatment challenges for an aging CF population. While CF transmembrane conductance regulator (CFTR) modulator therapy is effective for many CF manifestations, airway inflammation as a hallmark of CF lung disease is not consistently impacted leading to impaired mucus clearance and susceptibility to chronic airway infections. Therefore, it is of great interest to identify novel therapeutic approaches that improve CF-associated chronic inflammation, mucociliary dysfunction and recurrent infections to be ultimately applicable for all CF patients. We have recently published that Fibroblast Growth Factor (FGF) signaling, a well characterized pro-inflammatory and aging signaling pathway, is activated in CF lung disease. We hypothesize that FGF receptor (FGFR) inhibition will attenuate CF-associated inflammation and impaired mucociliary clearance. We will test our hypothesis by employing a multidisciplinary approach combining cell culture with animal models including a chronic airway infection model. Aim 1 will establish the effects of FGFR inhibition in vitro on airway inflammation and mucociliary clearance in the human CF lung using primary human bronchial epithelial cells, cultured at the air liquid interface from different CF genotypes. The in vivo Aim 2 will recapitulate these findings in established CF rat models and assess FGFR inhibition and its impact on CF-associated inflammation, muco-obstructive disease and lung function. Aim 3 will further establish FGFR modulation in the chronically infected CF lung in vivo. The overall aim of this proposal is to establish the role of FGFR modulation in CF associated lung complications as an amenable therapeutic target to ultimately improve functional outcomes, quality of life, and long-term survival in the growing population of aging individuals with CF.