Onametostat
Onametostat is an orally available small molecule inhibitor of protein arginine methyltransferase 5 (PRMT5), with potential antiproliferative and antineoplastic activities. Upon oral administration,onametostat selectively targets and irreversibly binds to the S-adenosylmethionine (SAM)- and substrate-binding pockets of the PRMT5/methylosome protein 50 (MEP50) complex, and inhibits its function. By inhibiting its methyltransferase activity, levels of both monomethylated and dimethylated arginine residues in histones H2A, H3 and H4 are decreased. This modulates the expression of genes involved in several cellular processes, including cellular proliferation. This may increase the expression of antiproliferative genes and/or decrease the expression of genes that promote cell proliferation, which may lead to decreased growth of rapidly proliferating cells, including cancer cells. PRMT5, a type II methyltransferase that catalyzes the formation of both omega-N monomethylarginine (MMA) and symmetric dimethylarginine (sDMA) on histones and a variety of other protein substrates involved in signal transduction and cellular transcription, is overexpressed in several neoplasms. Elevated levels are associated with decreased patient survival.