Abstract 503: ISM3412, a novel and selective MAT2A inhibitor for the treatment of cancer

Abstract The enzyme methionine adenosyltransferase 2α (MAT2A) has an important role in metabolism and epigenetics as the major producer of the universal methyl donor S-adenosyl methionine (SAM). Despite broad cellular functions, MAT2A was recently implicated as a synthetic lethal target in cancers that have a deletion of the methylthioadenosine phosphorylase (MTAP) gene, which is found in approximately 15% of all cancers. Here, we report ISM3412 is a novel potent MAT2A inhibitor with high selectivity. In enzymatic assays, ISM3412 demonstrated a strong inhibition of MAT2A with an IC50 of 19.4 nM. In both HCT116 MTAP-/- cells and HCT116 parental cells, the compound inhibited SAM production, with IC50 values of 5.97 nM and 3.66 nM, respectively. Additionally, it inhibited SDMA production in HCT116 MTAP-/- cells (IC50 of 6.37 nM), but not in HCT116 parental cells (IC50 > 2000 nM). Consistent with the large SDMA inhibitory potency difference between the HCT116 isogenic cell pair, ISM3412 also exhibited very good selectivity in cellular proliferation assays. While it inhibited cellular growth in HCT116 MTAP-/-cells with an IC50 of 199nM, its inhibitory potency on HCT116 parental cells was very weak (IC50 of >21117nM), revealing more than a 100-fold selectivity in inhibiting growth in this isogenic pair cell line. Furthermore, while ISM3412 strongly inhibited proliferation in multiple cancer cell lines with natural MTAP deficiency (including pancreatic cancer, bladder cancer, and NSCLC), the same was not observed in multiple MTAP-intact cell lines (IC50 > 30 uM). Consistent with the in vitro data, ISM3412 demonstrated robust mono-therapeutic efficacy in an MTAP-/- HCT116 CDX model with tumor growth inhibition of 66% at 3 mg/kg QD. Similarly, ISM3412 also demonstrated robust single-agent efficacy in CDX models of pancreatic cancer, bladder cancer and NSCLC, as well as in a PDX model of esophageal cancer. Notably, ISM3412 showed improved efficacy when combined with docetaxel, compared to the individual monotherapy. ISM3412, at 10 uM, showed no obvious agonistic or antagonistic effect on 44 selected targets in a mini safety panel, demonstrating its selectivity as a MAT2A inhibitor. In addition to its strong biological potency and selectivity, ISM3412 exhibited favorable drug-likeness properties, including low molecular weight, good solubility and permeability, and low plasma protein binding. In vivo PK data revealed low clearance and high oral-bioavailability. Further, it was well tolerated with no significant hepatobiliary toxicity. In conclusion, ISM3412 is a novel and highly selective MAT2A inhibitor for MTAP-deficient cancers, and merits clinical evaluation. Citation Format: Qingyuan Meng, Xiao Ding, Xiaosong Liu, Hailong Wang, Ling Wang, Junwen Qiao, Hua Cao, Yushu Yin, Congcong Zhu, Xing Liang, Xin Cai, Yuanyuan Xu, Chenxi Xu, Shan Chen, Sujata Rao, Feng Ren, Alex Zhavoronkov. ISM3412, a novel and selective MAT2A inhibitor for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 503.