To evaluate the efficacy of Y-ART-3 as an antiviral drug for HIV infections, its anti-HIV activity was assessed in vitro in cell culture systems and in vivo in hu-PBL-SCID mice. The results indicated that Y-ART-3 invariably inhibited not only HIV-1, but also HIV-2 and SIV strains. Its mechanism of action is ascribed to inhibition of viral adsorption to CD4-positive cells. In an in vivo study, human Ig- and CD4-positive cells were detected at similar levels in Y-ART-3-treated hu-PBL-SCID mice that were infected with HIV, and in PBS-treated control hu-PBL SCID mice that were not infected with HIV. If HIV positivity was calculated using the number of tests in which HIV was detected (i.e. PCR, and p24 from co-cultures of spleen and peritoneal wash cells), a significant effect of Y-ART-3 at a dose of 4 mg/kg was noted. Therefore, Y-ART-3 may be considered to be a potent and effective anti-HIV compound.