Pharmacological inhibition of CaMKK2 with the selective antagonist STO-609 regresses NAFLD

Binding of calcium to its intracellular receptor calmodulin (CaM) activates a family of Ca(2+)/CaM-dependent protein kinases. CaMKK2 (Ca(2+)/CaM-dependent protein kinase kinase 2) is a central member of this kinase family as it controls the actions of a CaMK cascade involving CaMKI, CaMKIV or AMPK. CaMKK2 controls insulin signaling, metabolic homeostasis, inflammation and cancer cell growth highlighting its potential as a therapeutic target for a variety of diseases. STO-609 is a selective, small molecule inhibitor of CaMKK2. Although STO-609 has been used extensively in vitro and in cells to characterize and define new mechanistic functions of CaMKK2, only a few studies have reported the in vivo use of STO-609. We synthesized functional STO-609 and assessed its pharmacological properties through in vitro (kinase assay), ex vivo (human liver microsomes) and in vivo (mouse) model systems. We describe the metabolic processing of STO-609, its toxicity, pharmacokinetics and bioavailability in a variety of mouse tissues. Utilizing these data, we show STO-609 treatment to inhibit CaMKK2 function confers protection against non-alcoholic fatty liver disease. These data provide a valuable resource by establishing criteria for use of STO-609 to inhibit the in vivo functions of CaMKK2 and demonstrate its utility for treating metabolically-related hepatic disease.