Tenofovir is an adenosine
analogue. Like AMP, the molecule consists of the base adenine and a phosphate group, but in between there is no deoxyribose (a five-carbon ring shaped structure) and there is no equivalent of the 3' carbon atom which forms phosphodiester linkages, so the backone of the DNA cannot be formed.
It acts as a selective inhibitor of the reverse transcriptase enzyme, which converts viral RNA into DNA, to be incorporated into human cells. It can thus be used to treat HIV as well as hepatitis B .
Because of the likelihood of viral mutations which might limit the action of this compound in inhibiting reverse transcritase, tenofovir needs to be used in combination with other drugs in highly active antiretroviral therapy
(HAART) treatments for HIV.