Newly Designed Six-Membered Azasugar Nucleotide-Containing Phosphorothioate Oligonucleotides as Potent Human Immunodeficiency Virus Type 1 Inhibitors

A series of modified oligonucleotides (ONs), characterized by a phosphorothioate (P=S) backbone and a six-membered azasugar (6-AZS) as a sugar substitute in a nucleotide, were newly synthesized and assessed for their ability to inhibit human immunodeficiency virus type 1 (HIV-1) via simple treatment of HIV-1-infected cultures, without any transfection process. While unmodified P=S ONs exhibited only minor anti-HIV-1 activity, the six-membered azasugar nucleotide (6-AZN)-containing P=S oligonucleotides (AZPSONs) exhibited remarkable antiviral activity against HIV-1/simian-human immunodeficiency virus (SHIV) replication and syncytium formation (50% effective concentration = 0.02 to 0.2 μM). The AZPSONs exhibited little cytotoxicity at concentrations of up to 100 μM. DBM 2198, one of the most effective AZPSONs, exhibited antiviral activity against a broad spectrum of HIV-1, including T-cell-tropic, monotropic, and even drug-resistant HIV-1 variants. The anti-HIV-1 activities of DBM 2198 were similarly maintained in HIV-1-infected cultures of peripheral blood mononuclear cells. When we treated severely infected cultures with DBM 2198, syncytia disappeared completely within 2 days. Taken together, our results indicate that DBM 2198 and other AZPSONs may prove useful in the further development of safe and effective AIDS-therapeutic drugs against a broad spectrum of HIV-1 variants.