TY - JOUR T1 - MK-8719, a Novel and Selective <em>O</em>-GlcNAcase Inhibitor That Reduces the Formation of Pathological Tau and Ameliorates Neurodegeneration in a Mouse Model of Tauopathy JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 252 LP - 263 DO - 10.1124/jpet.120.266122 VL - 374 IS - 2 AU - Xiaohai Wang AU - Wenping Li AU - Jacob Marcus AU - Michelle Pearson AU - Lixin Song AU - Karen Smith AU - Giuseppe Terracina AU - Julie Lee AU - Kwok-Lam Karen Hong AU - Sherry X. Lu AU - Lynn Hyde AU - Shu-Cheng Chen AU - David Kinsley AU - Jerry P. Melchor AU - Daniel J. Rubins AU - Xiangjun Meng AU - Eric Hostetler AU - Cyrille Sur AU - Lili Zhang AU - Joel B. Schachter AU - J. Fred Hess AU - Harold G. Selnick AU - David J. Vocadlo AU - Ernest J. McEachern AU - Jason M. Uslaner AU - Joseph L. Duffy AU - Sean M. Smith Y1 - 2020/08/01 UR - http://jpet.aspetjournals.org/content/374/2/252.abstract N2 - Deposition of hyperphosphorylated and aggregated tau protein in the central nervous system is characteristic of Alzheimer disease and other tauopathies. Tau is subject to O-linked N-acetylglucosamine (O-GlcNAc) modification, and O-GlcNAcylation of tau has been shown to influence tau phosphorylation and aggregation. Inhibition of O-GlcNAcase (OGA), the enzyme that removes O-GlcNAc moieties, is a novel strategy to attenuate the formation of pathologic tau. Here we described the in vitro and in vivo pharmacological properties of a novel and selective OGA inhibitor, MK-8719. In vitro, this compound is a potent inhibitor of the human OGA enzyme with comparable activity against the corresponding enzymes from mouse, rat, and dog. In vivo, oral administration of MK-8719 elevates brain and peripheral blood mononuclear cell O-GlcNAc levels in a dose-dependent manner. In addition, positron emission tomography imaging studies demonstrate robust target engagement of MK-8719 in the brains of rats and rTg4510 mice. In the rTg4510 mouse model of human tauopathy, MK-8719 significantly increases brain O-GlcNAc levels and reduces pathologic tau. The reduction in tau pathology in rTg4510 mice is accompanied by attenuation of brain atrophy, including reduction of forebrain volume loss as revealed by volumetric magnetic resonance imaging analysis. These findings suggest that OGA inhibition may reduce tau pathology in tauopathies. However, since hundreds of O-GlcNAcylated proteins may be influenced by OGA inhibition, it will be critical to understand the physiologic and toxicological consequences of chronic O-GlcNAc elevation in vivo.SIGNIFICANCE STATEMENT MK-8719 is a novel, selective, and potent O-linked N-acetylglucosamine (O-GlcNAc)-ase (OGA) inhibitor that inhibits OGA enzyme activity across multiple species with comparable in vitro potency. In vivo, MK-8719 elevates brain O-GlcNAc levels, reduces pathological tau, and ameliorates brain atrophy in the rTg4510 mouse model of tauopathy. These findings indicate that OGA inhibition may be a promising therapeutic strategy for the treatment of Alzheimer disease and other tauopathies. ER -