Azidothymidine (AZT), also known as Zidovudine (ZDV), is a thymidine
analogue. It has an unusual linear triple nitrogen group attached to carbon 3 of deoxyribose. In the DNA molecule, this atom, described as the 3' end, forms phosphodiester bonds with the next nucleotide.
It acts as a selective inhibitor of HIV's reverse transcriptase enzyme, which converts viral RNA into DNA, to be incorporated into human T lymphocyte cells.
Once converted into its triphosphate form it is incorporated into the developing proviral DNA chain (in competition with thymidine triphosphate dTTP) but it causes the chain to terminate, and the proviral DNA is not error-checked like the cell's normal DNA.
AZT in combination with other drugs can be used as highly active antiretroviral therapy
(HAART) treatments for HIV.