Abstract 1808: Discovery of highly selective novel MTA-cooperative PRMT5 inhibitors for the treatment of cancers

Abstract Protein arginine methyltransferase 5 (PRMT5), a type II PRMT catalyzing the formation of symmetric dimethylation of arginine residues on histone and non-histone proteins, regulates many biological pathways in mammalian cells, including cell growth and differentiation. Methylthioadenosine phosphorylase (MTAP) is required for the methionine salvage pathway, deletion of MTAP leads to the accumulation of inhibitory PRMT5 cofactor methylthioadenosine (MTA). MTAP gene is adjacent to and frequently co-deleted with CDKN2A gene, the most commonly deleted tumor suppressor gene in human cancers. The increase in MTA significantly reduced PRMT5 activity in MTAP-deficient cancer cells, rendering them more vulnerable to PRMT5 inhibition than normal cells. Selective Inhibitors of PRMT5-MTA complex (MTA-cooperative) are supposed to exhibit an increased therapeutic index compared to first generation PRMT5 inhibitors for the treatment of MTAP-deleted (MTAP-del) cancer patients. Guided by computation-aided drug design (CADD), binding mode analysis of known PRMT5 inhibitors has led to the design and synthesis of a novel series of MTA-cooperative PRMT5 inhibitors. Many compounds within this series were found to inhibit PRMT5/MEP50 complex with single digit nM of IC50 in enzymatic assay. Cell based activity of these compounds was assessed by measuring the symmetric demethylarginine (SDMA) and 10-day cell proliferation assays. Several compounds exhibited low double-digit nM of cellular potency in HCT116 MTAP-del cells, the inhibition of SDMA and anti-proliferation activities in HCT116 MTAP-del cells over HCT116 MTAP-WT cells have excellent selectivity (80 - 400 fold). Further optimization of in vitro and in vivo pharmacokinetic properties has yielded candidate compounds suitable for evaluation of pharmacodynamic effect in the LU99 MTAP-del NSCLC xenograft model. Tumor growth inhibition (TGI) was observed in a dose-dependent manner, accompanied by a reduction of PRMT5-mediated SDMA levels in both the tumor and bone marrow. In summary, we have identified compounds with novel scaffolds that are potent and highly selective MTA-cooperative PRMT5 inhibitors. Further development of the second-generation PRMT5 inhibitors for treatment of cancers is also planned. Citation Format: Wen-Lian Wu, Taishan Hu, Zhilin Deng, Honghai Li, Quanrong Shen, Lei Zhang, Xiaochu Ma, Peihua Sun, Cindy Cheng, Fang Liu, Xin Chen, Ye Hua, Bryan Huang. Discovery of highly selective novel MTA-cooperative PRMT5 inhibitors for the treatment of cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 1808.