CMP-5 dihydrochloride is a potent, specific, and selective PRMT5 inhibitor, while displays no activity against PRMT1 , PRMT4 , and PRMT7 enzymes. CMP-5 dihydrochloride selectively blocks S2Me-H4R3 by inhibiting PRMT5 methyltransferase activity on histone preparations. CMP-5 dihydrochloride prevents EBV-driven B-lymphocyte transformation but leaving normal B cells unaffected.