Covalent S-Adenosylhomocysteine-Based DNA Methyltransferase 2 Inhibitors with a New Type of Aryl Warhead

The DNA methyltransferase 2 (DNMT2) is an RNA modifying enzyme associated with pathophysiological processes, such as mental and metabolic disorders or cancer. Although the development of methyltransferase inhibitors remains challenging, DNMT2 is not only a promising target for drug discovery, but also for the development of activity-based probes. Here, we present covalent SAH-based DNMT2 inhibitors decorated with a new type of aryl warhead. Based on a noncovalent DNMT2 inhibitor with N-benzyl substituent, the Topliss scheme was followed for optimization. The results showed that electron-deficient benzyl moieties highly increased affinity. By decorating the structures with strong electron-withdrawing moieties and leaving groups, we adjusted the electrophilicity to create covalent DNMT2 inhibitors. A 4-bromo-3-nitrophenylsulfonamide-decorated SAH derivative (80) turned out to be the most potent (IC₅₀ = 1.2 ± 0.1 μM) and selective inhibitor. Protein mass spectrometry confirmed the covalent reaction with the catalytically active cysteine-79.