Osmolytes and ion transport modulators: new strategies for airway surface rehydration

Mucociliary clearance (MCC) in CF lung disease is limited by airway dehydration, leading to persistent bacterial infection and inflammation in the airways. Agents designed to rehydrate the airway mucosa lead to improved MCC. Hyperosmolar agents, such as hypertonic saline and mannitol, create a luminal osmotic gradient, drawing water into the dehydrated ASL. Ion transport modulators function to activate alternative chloride channels and/or to block sodium hyperabsorption that occurs through a dysregulated ENaC channel. Combinations of these therapies may result in a synergistic improvement in airway hydration, and thus, restore MCC. Active ongoing phase II and III trials of new pharmacotherapeutics are covered in this review.