Design, synthesis and evaluation of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one derivatives as novel MTA cooperative PRMT5 inhibitors for the treatment of MTAP-deleted cancers.

Protein arginine methyltransferase 5 (PRMT5) has emerged as a promising therapeutic target due to its critical roles in regulating fundamental cellular processes such as proliferation, migration, and differentiation. Although several PRMT5 inhibitors have been reported, but none have gained clinical approval. Herein, we describe the discovery of a novel series of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones derivatives as MTA cooperative PRMT5 inhibitors. Compound 9u exhibited significant antiproliferative activity in MTAP-deleted HCT116 cancer cells, with an IC50 value of 13 nM, exhibiting 70-fold selectivity over MTAP wild type HCT116 cells. Furthermore, 9u displayed robust efficacy across diverse MTAP-deleted cancer cell lines, achieving IC50 values of <1.5-51 nM. Notably, it also showed favorable metabolic stability in both human and mouse liver microsomes. These findings establish a promising lead for the development of PRMT5-MTA inhibitors specifically targeting MTAP-deficient cancers.