ANTISENSE OLIGONUCLEOTIDE PHOSPHOROTHIOATES AGAINST HUMAN-IMMUNODEFICIENCY-VIRUS

Various types of antisense oligonucleotide constructs were synthesized for screening against human immunodeficiency virus (HIV) in two different cell culture assays. Nuclease-resistant internucleoside linkages that were studied included non-ionic methyl phosphonates [5'O-P(O)CH3-O3'] and, primarily, negatively charged phosphorothioates [5'O-P(O)S-O3']. Previously reported results, which had been obtained in a de novo infection assay that measured inhibition of the cytopathic effect of HIV-1, revealed an unexpected sequence-non-specific antiviral effect for phosphorothioate oligomers. The mechanistic basis for this potent antiviral activity (100% at 0.5-1-mu-M) is not clearly established at this time. In contrast, the companion results derived from a chronically HIV-1-infected cell assay indicated that phosphorothioate oligomers directed against HIV-1 rev RNA also exhibit sequence-specific inhibition of gene expression, albeit at higher concentrations in this system (50% at 5-mu-M) relative to the de novo infection assay. More recently, alternative targets in HIV-1 RNA, and alternative types of modified oligomers, were examined but none of these had significantly higher activity then the anti-rev phosphorothioate sequence previously reported. Collaborative studies have been directed at the first pharmacokinetic measurements using fluorescently and radioactively (S-35) labelled versions of the anti-rev phosphorothioate. Efforts are underway to achieve relatively low-cost large-scale synthesis of this antisense oligonucleotide phosphorothioate as a prelude for clinical trials against acquired immunodeficiency syndrome (AIDS).