PRMT5 is an important protein arginine methyltransferase that catalyzes the symmetric dimethylation of arginine resides on histones or non-histone substrate proteins.It has been thought as a promising target for many diseases,particularly cancer.Despite the potential applications of PRMT5 inhibitors in cancer treatment,very few of PRMT5i have been publicly reported.In this investigation,virtual screening and structure-activity relationship(SAR)studies were carried out to discovery novel PRMT5i,which finally led to the identification of a number of new PRMT5i.The most active compound,P5i-6,exhibited a considerable inhibitory potency against PRMT5 with an IC50 value of 0.57μM,and a high selectivity for PRMT5 against other tested PRMTs.It displayed a very good anti-viability activity against two colorectal cancer cell lines,HT-29 and DLD-1,and one hepatic cancer cell line,HepG2,in a sensitivity assay against 36 different cancer cell lines.Western Blot assays indicated that P5i-6 selectively inhibited the symmetric dimethylations of H4R3 and H3R8 in DLD-1 cells.Overall,P5i-6 could be used as a chemical probe to investigate new functions of PRMT5 in biology and also served as a good lead compound for the development of new PRMT5-targeting therapeutic agents.