Aerosolized Hypertonic Xylitol Versus Hypertonic Saline in Cystic Fibrosis (CF) Subjects

Overview

Cystic fibrosis (CF) lung disease is characterized by chronic bacterial colonization and recurrent infection of the airways. Lowering the airway surface liquid (ASL) salt concentration has been shown to increase activity of salt sensitive antimicrobial peptides. Xylitol is a 5-carbon sugar that can lower the ASL salt concentration, thus enhancing innate immunity. In this study, the investigators propose to test the safety and tolerability of aerosolized xylitol used daily for 2 weeks in subjects with cystic fibrosis. In a pilot, 2-week study, 60 subjects with cystic fibrosis with an FEV1(Forced expiratory volume in 1 second ) \>30% predicted will be randomized to receive aerosolized 7% hypertonic saline (5 ml) or 15% xylitol, (5 ml) twice a day for 14 days. The primary outcomes will be safety as assessed by FEV1 change from baseline, adverse events and respiratory symptom score. Outcomes for trend in efficacy include density of colonization of sputum, time to next exacerbation, sputum cytokines and revised CF quality of life questionnaire.

Cystic fibrosis (CF) lung disease is characterized by chronic bacterial colonization and recurrent infection of the airways. Disruption of the cystic fibrosis transmembrane conductance regulator chloride channels in subjects with CF results in altered fluid and electrolyte transport across the airway epithelium thereby initiating infections. These infections eventually destroy the lungs and contribute to significant morbidity and mortality in patients with CF. It is well known that antibacterial activity of innate immune mediators such as lysozyme and beta defensins in human airway surface liquid (ASL) is salt-sensitive; an increase in salt concentration inhibits their activity. Conversely, their activity is increased by low ionic strength. Lowering the ASL salt concentration and increasing the ASL volume might therefore potentiate innate immunity and therefore decrease or prevent airway infections in subjects with CF. Xylitol, a five-carbon sugar with low transepithelial permeability, which is poorly metabolized by bacteria can lower the salt concentration of both cystic fibrosis (CF) and non-CF epithelia in vitro. Xylitol is an artificial sweetener that has been successfully used in chewing gums to prevent dental caries; it has been used as an oral sugar substitute without significant adverse effects. It has also been shown to decrease the incidence of acute otitis media by 20-40%; nasal application to normal human subjects was found to decrease colonization with coagulase negative staphylococcus. We found that aerosolized iso-osmolar xylitol was safe in mice, healthy volunteers and stable subjects with CF when administered over a single day. In a recent study, we observed that single doses of 10% followed by 15% xylitol was well tolerated by subjects with cystic fibrosis who were stable. In this pilot study we propose to test the hypothesis that aerosolized hypertonic xylitol given daily for 2 weeks, will be safe and well tolerated and potentially lower the density of colonization in subjects with CF compared to hypertonic saline. We chose hypertonic concentration of xylitol to be comparable in part to hypertonic saline which is being offered as a routine treatment in hospitalized patients with CF exacerbation.