Biologically active oligodeoxyribonucleotides--IX. Synthesis and anti-HIV-1 activity of hexadeoxyribonucleotides, TGGGAG, bearing 3'- and 5'-end-modification.

We have determined that hexadeoxyribonucleotides (5'TGGGAG3'), with modified aromatic groups such as a trityl group at the 5'-end, have anti-HIV-1 activity in vitro. The 6-mer bearing a 3,4-dibenzyloxybenzyl (3,4-DBB) group at the 5'-end had the most potent activity and the least cytotoxicity. When the 3'-end of the 5'-(3,4-DBB)-modified 6-mer was substituted with a 2-hydroxyethylphosphate, a 2-hydroxyethylthiophosphate, or a methylphosphate group at the 3'-end, anti-HIV-1 activity increased. Moreover, among various 3'- and 5'-end-modified 6-mers that were tested, the 6-mer (R-95288) bearing a 3,4-DBB group at the 5'-end and a 2-hydroxyethylphosphate group at the 3'-end was the most stable, when incubated with mouse, rat, or human plasma. Therefore, R-95288 was chosen as the best candidate for possible use in therapy on the basis of its anti-HIV-1 activity.