Discovery of AMG 193, an MTA-Cooperative PRMT5 Inhibitor for the Treatment of MTAP-Deleted Cancers

MTAP deletion occurs in 10-15% of all human cancers due to its proximity to the tumor suppressor gene CDKN2A. The loss of MTAP leads to accumulation of methylthioadenosine (MTA), which shares structural similarity to S-adenosyl methionine (SAM), the methyl donor for the cell-essential protein arginine methyltransferase 5 (PRMT5). By competing with SAM, MTA partially inhibits PRMT5, making MTAP-deleted tumors susceptible to further PRMT5 inhibition. Herein, we report the discovery of MTA-cooperative PRMT5 inhibitor AMG 193, a molecule that inhibited the proliferation of HCT116 MTAP-deleted cells with ∼40x selectivity over HCT116 MTAP-WT cells. AMG 193 was orally efficacious in mouse xenografts of endogenous MTAP-null tumors such as BxPC-3 (96% TGI @ 100 mg/kg QD) and U87MG (88% TGI @ 100 mg/kg QD). Preclinical data indicate that AMG 193 is brain-penetrant. AMG 193 is currently in Phase I/II clinical trials for the treatment of advanced MTAP-deleted solid tumors.