Like AZT, ddI and ddC, TSAO derivatives are modified forms of one of the building blocks of DNA (known as nucleosides). When HIV replicates in the presence of these nucleoside analogue drugs, the virus's reverse transcriptase enzyme incorporates the drug in the place of a normal nucleoside in the growing DNA strand. This prevents the proper assembly of viral genetic material and halts viral replication.

Like the non-nucleoside reverse transcriptase inhibitors, these drugs are active only against HIV-1 and have no effect against HIV-2 or SIV.

Current use

TSAO derivatives are unlicensed, experimental drugs that are still at a very early stage of development. Trials in humans have not yet begun.

Key research

References

Balzarini J et al. 2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5-(4-amino-1,2-oxathio le-2,2-dioxide)-pyrimidine (TSAO) nucleoside analogues: highly selective inhibitors of human immunodeficiency virus type 1 that are targeted at the viral reverse transcriptase. PNAS USA 89(10):4392-4396, 1992.

Balzarini J et al. Human immunodeficiency virus type 1-specific 2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5-(4-amino-1,2-oxathio le-2,2-dioxide)-purine analogues show a resistance spectrum that is different from that of the human immunodeficiency virus type 1-specific non-nucleoside analogues. Mol Pharmacol 43(1):109-114, 1993.