PRMT5-MTA-IN-1 (Compound A9a) is an inhibitor for protein arginine methyltransferase PRMT5-MTA. PRMT5-MTA-IN-1 inhibits the proliferation of colorectal cancer cell HCT116 wildtype and MTAP del mutant, with an IC 50 of 16 nM and 2.47 μM. PRMT5-MTA-IN-1 exhibits good liver microsomal stability and film permeability. PRMT5-MTA-IN-1 exhibits good pharmacokinetic characteristics in CD-1 mice.