Abstract 1768: Pharmacological inhibition of METTL1 as a novel therapeutic strategy against aggressive malignancies

METTL1 catalyzes N7-methylation of guanine (m7G) in a subset of transfer RNAs (tRNAs). We have shown that METTL1 is a promising therapeutic target for various malignancies, including acute myeloid leukemia (AML), melanoma, and pancreatic ductal adenocarcinoma (PDAC). Here, we present characterization of STM9005, a novel small-molecule inhibitor of METTL1, as an effective therapeutic strategy against cancer.Aims: To evaluate the therapeutic potential of STM9005, a novel and bioavailable METTL1 tRNA methyltransferase inhibitor, in aggressive malignancies. Methods: High-throughput screening and subsequent chemical optimization identified STM9005 as a potent small-molecule inhibitor of the catalytic activity of METTL1. STM9005 was tested in vitro to assess its impact on cancer models, including effects on growth, differentiation, and cell cycle regulation. RNA sequencing, m7G profiling of tRNAs, and proteome analysis identified molecular pathways affected by the inhibition of METTL1. In vivo experiments assessed therapeutic efficacy in solid and hematological cancer models. Results: The impact of STM9005 was measured by cellular mechanistic assays and modification-induced misincorporation tRNA sequencing, revealing decreased m7G methylation and lower levels of target tRNAs. The efficacy of STM9005 was determined in a panel of cancer models, including AML, melanoma, and PDAC. METTL1 inhibition impaired cell proliferation and viability in multiple cancer models, with no effects in non-cancerous cells, suggesting a cancer-specific mechanism of action. In vitro treatment with STM9005 led to significant differentiation of AML, suggesting an important connection between m7G and status of oncogenesis. STM9005 treatment also reduced cell cycle progression and downregulated cell cycle oncogenes. Mechanistic interrogation using m7G profiling of tRNAs, RNA sequencing, and proteome analysis identified drug-specific changes at both RNA and protein levels. In vivo characterization of STM9005 demonstrated excellent bioavailability in mice with no detectable toxicity. We evaluated its anti-cancer effects across a range of aggressive cancer models, including melanoma, PDAC, and AML patient-derived xenografts (PDX). Daily administration of STM9005 significantly inhibited disease progression, indicating potent anti-cancer activity. Target engagement was confirmed by reduced m7G levels on METTL1-dependent tRNA substrates. Summary We describe STM9005 as a first-in-class inhibitor targeting the tRNA methyltransferase METTL1. Small-molecule inhibition of METTL1 demonstrates potent anti-cancer effects in vitro and in vivo using physiologically and clinically relevant models of advanced malignancies. These findings provide proof-of-concept that pharmacological inhibition of METTL1 offers a novel therapeutic strategy for aggressive cancers with unmet clinical needs. Citation Format: Eliza Yankova, Alexandra Sapetschnig, Beth Thomas, Sian Evans, Maria Eleftheriou, James Russell, Vidur Tandon, Natalie Webster, Harry Fischl, Sarah Bucknell, George S. Vassiliou, Walid T. Khaled, Maria P. Alcolea, Oliver Rausch, Konstantinos Tzelepis. Pharmacological inhibition of METTL1 as a novel therapeutic strategy against aggressive malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1768.