AMD-3451 free base is a dual CCR5 CXCR4 antagonist which may be useful in the treatment of a wide variety of R5, R5 X4, and X4 strains of human immunodeficiency virus type 1 (HIV-1) and HIV-2. AMD3451 is the first low-molecular-weight anti-HIV agent with selective HIV coreceptor, CCR5 and CXCR4, interaction.