Modulators of Na/K-ATPase: a patent review

INTRODUCTION: Na/K-ATPase is a heterodimeric transmembrane protein that regulates neuronal signaling, ion homeostasis, muscle contraction and substrate transportation. Modulators of Na/K-ATPase inhibit Na(+)/K(+) exchange and increase cytosolic Ca(2+) to induce inotropic activity in heart failure patients. Besides producing inotropic effects, the Na/K-ATPase acts as a signal transducer for the regulation of many cellular events, including those associated with tumor cell growth. This has aroused new interest for development of Na/K-ATPase inhibitors as anticancer agents. AREAS COVERED: This article summarizes the various Na/K-ATPase inhibitors that have shown biological importance in clinical study and drug development for inotropic and anticancer agents. EXPERT OPINION: The field of Na/K-ATPase modulators has attracted much interest in the past because of their clinical implication in heart failure treatments. Recent studies have shown that Na/K-ATPase modulators are capable of producing profound anticancer effects upon binding to the Na/K-ATPase. Interestingly, certain Na/K-ATPase isoforms are highly expressed in particular cancer cells, providing the opportunity for a Na/K-ATPase modulator to selectively target these cellular abnormalities. Indeed the most well-known Na/K-ATPase modulators, cardiac glycosides, have shown both strong binding affinity and moderate selectivity for isoforms. It is anticipated, in the future, that the further development of more selective and potent Na/K-ATPase modulators will take place, which in turn could lead to a more effective treatment for either heart failure or cancer.