A synthetic antiviral acyclic nucleotide analogue of adenosine 5-monophosphate. Tenofovir is incorporated into human immunodeficiency viral DNA instead of the natural substrate deoxyadenosine 5-triphosphate, thereby inhibiting HIV-1 reverse transcriptase (RT), an RNA-dependent DNA polymerase, and resulting in DNA chain termination and impairment of viral replication and propagation. This agent prevents HIV from reproducing in uninfected cells only. Tenofovir exhibits activity against the hepatitis B virus (HBV). (NCI04)