Synthesis and In Vitro Characterization of OGA-2506 as a High Affinity Radioligand for O-GlcNAcase

Abstract

O-GlcNAcase (OGA) is a glycoside hydrolase that regulates protein O-GlcNAcylation, a dynamic post-translational modification implicated in numerous cellular processes. Dysregulation of OGA alters cellular O-GlcNAc homeostasis and has been linked to neurodegenerative and other chronic diseases. The development of radioligands targeting OGA, particularly those derived from well-characterized tool compounds, could substantially advance drug discovery in this area. Herein, we report the radiosynthesis of a novel tritium (3H)-labeled radioligand 7 (code name [3H]OGA-2506) derived from a chiral piperidine scaffold, and its preliminary in vitro binding evaluation. Starting from iodine precursor 8, palladium-catalyzed tritiation afforded [3H]7 with excellent molar activity (1822 GBq/mmol) and high radiochemical purity (>99%). Saturation binding studies revealed that [3H]7 binds OGA with high affinity to rat striatum homogenates (Kd = 3.56 nM; Bmax = 42.62 nM). Competition assays yielded an IC50 of 5.55 nM, and preliminary autoradiography demonstrated heterogeneous regional distribution in the brain with specific binding. These findings highlight [3H]7 as a valuable tool for OGA binding studies and provide a foundation for the future development of novel positron emission tomography (PET) ligands to probe O-GlcNAc signaling in the brain.