Cystic fibrosis (CF) is characterized by lack of hydration in the airways by impaired functioning of cystic fibrosis transmembrane conductance regulator (CFTR), leading to infection, inflammation and lung tissue damage. It is hypothesized that inhibiting the epithelial sodium channel (ENaC) in the airways in CF may enhance the mucociliary clearance (MCC) and provide clinical benefit, but numerous inhaled ENaC blockers have failed in clinical trials. Enterprise Therapeutics Ltd. is developing an inhaled ENaC blocker compound, ETD-001, for the treatment of CF.