Boromycin is a boron-containing macrolide antibiotic that has been found in Streptomyces. Boromycin inhibits growth of B. subtilis (MIC = 0.05 μg ml) and induces efflux of potassium ions from B. subtilis without affecting Na+ K+-ATPase activity. It decreases the synthesis of protein, RNA, and DNA in B. subtilis when used at a concentration of 0.05 μg ml. It inhibits the growth of B. halodurans (MIC = 10 ng ml) and inhibits the futalosine pathway of menaquinone synthesis in B. halodurans. Boromycin (3.4 nM) reverses bleomycin-induced cell cycle arrest at the G2 phase in Jurkat cells. It inhibits replication of the HIV-1 strains LAV-1 and RF and the HIV-2 strain LAV-2 in MT-4 cells (IC50s = 0.008, 0.11, and 0.007 μM, respectively). It also inhibits replication of a clinical isolate of HIV-1, strain KK-1, in MT-4 cells and peripheral blood mononuclear cells (PBMCs; IC50s = 0.14 and <0.1 μM, respectively).
KRH-1636 is an orally active, selective and extremely potent CXC chemokine receptor 4 antagonist. KRH-1636 exhibits a potent and selective anti-HIV-1 activity. KRH-1636 efficiently blocked replication of various T cell line-tropic (X4) HIV type 1 (HIV-1) in MT-4 cells and peripheral blood mononuclear cells through the inhibition of viral entry and membrane fusion via the CXC chemokine receptor (CXCR)4 coreceptor but not via CC chemokine receptor 5. KRH-1636 also inhibits binding of the CXC chemokine, stromal cell-derived factor 1alpha, to CXCR4 specifically and subsequent signal transduction. KRH-1636 prevented monoclonal antibodies from binding to CXCR4 without down-modulation of the coreceptor. KRH-1636 seems to be a promising agent for the treatment of HIV-1 infection.