Discovery of a potent, selective and cell active inhibitor of m6A demethylase ALKBH5

AlkB homolog 5 (ALKBH5) is an RNA m6A demethylase involved in the regulation of genes transcription, translation and metabolism and has been considered as a promising therapeutic target for various human diseases, especially cancers. However, there is still a lack of potent and selective ALKBH5 inhibitors. Herein, we report a new class of ALKBH5 inhibitors containing the 1-aryl-1H-pyrazole scaffold, which were obtained through fluorescence polarization-based screening, structural optimization and structure-activity relationship analysis. Among these compounds, 20m was the most potent one, which showed an IC50 value of 0.021 μM in fluorescence polarization assay. Compound 20m exhibited high selectivity towards ALKBH5 versus FTO as well as other AlkB subfamily members, indicating good selectivity for ALKBH5. Cellular thermal shift assay (CETSA) analysis showed that 20m could efficiently stabilize ALKBH5 in HepG2 cells. Dot blot assay demonstrated that 20m could increase m6A level in intact cells. Collectively, 20m is a potent, selective and cell active ALKBH5 inhibitor and could be used as a versatile chemical probe to explore the biological function of ALKBH5.