Small Molecular Compounds Inhibit HIV-1 Replication through Specifically Stabilizing APOBEC3G

APOBEC3G (hA3G) is a host inhibitor for human immunodeficiency virus, type 1 (HIV-1). However, HIV-1 Vif binds hA3G and induces its degradation. We have established a screening system to discover inhibitors that protect hA3G from Vif-mediated degradation. Through screening, compounds IMB-26 and IMB-35 were identified to be specific inhibitors for the degradation of hA3G by Vif. The inhibitors suppressed HIV-1 replication in hA3G-containing cells but not in those without hA3G. The anti-HIV effect correlated with the endogenous hA3G level. HIV-1 particles from hA3G(+) cells treated with IMB-26/35 contained a hA3G level higher than that from those without IMB-26/35 treatment and showed decreased infectivity. IMB-26/35 bound directly to the hA3G protein, suppressed Vif/hA3G interaction, and therefore protected hA3G from Vif-mediated degradation. The compounds were safe with an anti-HIV therapeutic index >200 in vitro. LD₅₀ of IMB-26 in mice was >1000 mg/kg (intraperitoneally). Therefore, IMB-26 and IMB-35 are novel anti-HIV leads working through specific stabilization of hA3G.