Discovery of 5‑Azaindole Inhibitors of O‑GlcNAcase for the Treatment of Alzheimer's Disease and Related Tauopathies

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by extracellular Amyloid-β plaque accumulation and intracellular tau neurofibrillary tangles, with tau pathology correlating more closely with cognitive decline. Modulation of tau phosphorylation through the regulation of O-GlcNAcylation, a post-translational modification controlled by O-GlcNAcase (OGA), represents a promising therapeutic strategy. In this study, we report the optimization of a pyrimidine hit identified by high-throughput screening, leading to the discovery and optimization of a novel series of 5-azaindole-based OGA inhibitors. From this series, compound 24 was identified as an in vivo tool candidate that demonstrated a favorable pharmacokinetic profile and measurable brain exposure. Pharmacodynamic studies in murine models demonstrated that compound 24 induced a significant and transient elevation of brain O-GlcNAcylation levels, confirming the in vivo target engagement. These findings underscore the potential of 5-azaindole-based OGA inhibitors as a novel validated chemotype for modulation of O-GlcNAcylation.