Abstract: Provided herein are O-GlcNAc transferase (OGT) inhibitor compounds of Formula (I), and pharmaceutically acceptable salts, solvates, hydrates, polymorphs, co-crystals, tautomers, stereoisomers, isotopically labeled derivatives, prodrugs, and compositions thereof. Also provided are methods and kits involving the inventive compounds or compositions for treating and/or preventing diseases (e.g., diabetes and complications thereof, neurodegenerative diseases, proliferative diseases such as cancers, autoimmune diseases, and inflammatory diseases) in a subject. Provided are methods of inhibiting OGT in a subject or biological sample.