KRH-3955 is a CXCR4 antagonist with good bioavailability and potent anti-HIV-1 activity. KRH-3955 can effectively inhibit the replication of X4 HIV-1 , including clinical isolates from different donors. KRH-3955 also shows activity against recombinant X4 HIV-1 containing reverse transcriptase , protease and tyrosinase resistance mutations. KRH-3955 can inhibit the binding of SDF-1alpha to CXCR4 and calcium ion signaling through this receptor. KRH-3955 inhibits the binding of an antibody against CXCR4 to CXCR4 , showing a potent antagonistic effect on CXCR4. KRH-3955 shows an oral bioavailability of 25.6% in rats and can inhibit the replication of X4 HIV-1 in vivo.