Small-molecule inhibition of METTL3 as a strategy against myeloid leukaemia.

N6-methyladenosine (m6A) is an abundant internal RNA modification1,2 that is catalysed predominantly by the METTL3-METTL14 methyltransferase complex3,4. The m6A methyltransferase METTL3 has been linked to the initiation and maintenance of acute myeloid leukaemia (AML), but the potential of therapeutic applications targeting this enzyme remains unknown5-7. Here we present the identification and characterization of STM2457, a highly potent and selective first-in-class catalytic inhibitor of METTL3, and a crystal structure of STM2457 in complex with METTL3-METTL14. Treatment of tumours with STM2457 leads to reduced AML growth and an increase in differentiation and apoptosis. These cellular effects are accompanied by selective reduction of m6A levels on known leukaemogenic mRNAs and a decrease in their expression consistent with a translational defect. We demonstrate that pharmacological inhibition of METTL3 in vivo leads to impaired engraftment and prolonged survival in various mouse models of AML, specifically targeting key stem cell subpopulations of AML. Collectively, these results reveal the inhibition of METTL3 as a potential therapeutic strategy against AML, and provide proof of concept that the targeting of RNA-modifying enzymes represents a promising avenue for anticancer therapy

Targeting the m(6)A RNA modification pathway blocks SARS-CoV-2 and HCoV-OC43 replication

N-6-methyladenosine (m(6)A) is an abundant internal RNA modification, influencing transcript fate and function in uninfected and virus-infected cells. Installation of m(6)A by the nuclear RNA methyltransferase METTL3 occurs cotranscriptionally; however, the genomes of some cytoplasmic RNA viruses are also m(6)A-modified. How the cellular m(6)A modification machinery impacts coronavirus replication, which occurs exclusively in the cytoplasm, is unknown. Here we show that replication of SARS-CoV-2, the agent responsible for the COVID-19 pandemic, and a seasonal human beta-coronavirus HCoV-OC43, can be suppressed by depletion of METTL3 or cytoplasmic m(6)A reader proteins YTHDF1 and YTHDF3 and by a highly specific small molecule METTL3 inhibitor. Reduction of infectious titer correlates with decreased synthesis of viral RNAs and the essential nucleocapsid (N) protein. Sites of m(6)A modification on genomic and subgenomic RNAs of both viruses were mapped by methylated RNA immunoprecipitation sequencing (meRIP-seq). Levels of host factors involved in m(6)A installation, removal, and recognition were unchanged by HCoV-OC43 infection; however, nuclear localization of METTL3 and cytoplasmic m(6)A readers YTHDF1 and YTHDF2 increased. This establishes that coronavirus RNAs are m(6)A-modified and host m(6)A pathway components control beta-coronavirus replication. Moreover, it illustrates the therapeutic potential of targeting the m(6)A pathway to restrict coronavirus reproduction

Probing Mechanisms of CYP3A Time-Dependent Inhibition Using a Truncated Model System

Time-dependent inhibition (TDI) of cytochrome P450 (CYP) enzymes may incur serious undesirable drug–drug interactions and in rare cases drug-induced idiosyncratic toxicity. The reactive metabolites are often generated through multiple sequential biotransformations and form adducts with CYP enzymes to inactivate their function. The complexity of these processes makes addressing TDI liability very challenging. Strategies to mitigate TDI are therefore highly valuable in discovering safe therapies to benefit patients. In this Letter, we disclose our simplified approach toward addressing CYP3A TDI liabilities, guided by metabolic mechanism hypotheses. By adding a methyl group onto the α carbon of a basic amine, TDI activities of both the truncated and full molecules (<b>7a</b> and <b>11</b>) were completely eliminated. We propose that truncated molecules, albeit with caveats, may be used as surrogates for full molecules to investigate TDI

Figure S1 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

Proliferation + Apoptosis assays</p

Table S6 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

LMOs for sc-RNA sequencing</p

Figure S2 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

Gene expression changes + pathways</p

Figure S3 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

METTL3 KD in B16 cell line</p

Figure S5 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

Co-culture assays + human PBMC data</p

Figure S6 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

PDL1 expression + STM3006 pharmacokinetic studies</p

Table S2 from Inhibition of METTL3 Results in a Cell-Intrinsic Interferon Response That Enhances Antitumor Immunity

Flow antibodies</p