METTL3 Inhibitors for Epitranscriptomic Modulation of Cellular Processes

The methylase METTL3 is the writer enzyme of the N6‐methyladenosine (m6A) modification of RNA. Using a structure‐based drug discovery approach, we identified a METTL3 inhibitor with potency in a biochemical assay of 280 nM, while its enantiomer is 100 times less active. We observed a dose‐dependent reduction in the m6A methylation level of mRNA in several cell lines treated with the inhibitor already after 16 h of treatment, which lasted for at least 6 days. Importantly, the prolonged incubation (up to 6 days) with the METTL3 inhibitor did not alter levels of other RNA modifications (i. e., m1A, m6Am, m7G), suggesting selectivity of the developed compound towards other RNA methyltransferases. Writer's block: We developed and characterized a small‐molecule inhibitor of m6A writer METTL3 by protein crystallography, biochemical and cellular assays. It shows high‐nanomolar potency in the biochemical assay, good selectivity against a panel of protein methyltransferases and kinases, and it reduced m6A/A ratio in mRNAs of different cell lines. In addition, we confirmed the selectivity of our compound towards other RNA methyltransferases in living cells.