Amiloride-sensitive, ENaC-mediated, active absorption of Na⁺ is elevated in airway epithelium of cystic fibrosis patients resulting in excess fluid removal from the airway lumen. This excess fluid/volume absorption corresponds to cystic fibrosis transmembrane regulator-linked defects in ENaC regulation resulting in the reduced mucociliary clearance found in CF airways. Here we show that INO-4995, a synthetic analog of the intracellular signaling molecule, inositol 3,4,5,6 tetrakisphosphate, inhibits Na⁺ and fluid absorption across cystic fibrosis airway epithelia, thus alleviating this critical pathology. This conclusion was based on electrophysiological studies, fluid absorption and ²²Na⁺ flux measurements in cystic fibrosis airway epithelia contrasted with normal epithelia and on electrophysiological studies in MDCK cells and 3T3 cells overexpressing ENaC. The effects of INO-4995 were long-lasting, dose-dependent and more pronounced in epithelia from cystic fibrosis patients vs. controls. These findings support preclinical development of INO-4995 for cystic fibrosis treatment and demonstrate for the first time the therapeutic potential of inositol polyphosphate derivatives.