Abacavir is a nucleoside reverse transcriptase inhibitor used for treatment of HIV infection (either alone or in combination with other antiviral drugs). It was shown that abacavir exerts its antiviral activity through its active metabolite, carbovir triphosphate. Carbovir triphosphate is a guanine analogue and a potent and selective inhibitor of viral reverse transcriptases. Upon administration, abacavir is first converted to abacavir monophosphate by ADK, then the monophosphate is deaminated to carbovir monophosphate, which is then anabolized by cellular kinases to carbovir diphosphate and then finally to carbovir triphosphate. Abacavir causes hypersensitivity reaction in patients with HLA-B*57:01 allele.

Efavirenz (brand names Sustiva® and Stocrin®) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) and is used as part of highly active antiretroviral therapy (HAART) for the treatment of a human immunodeficiency virus (HIV) type 1. For HIV infection that has not previously been treated, efavirenz and lamivudine in combination with zidovudine or tenofovir is the preferred NNRTI-based regimen. Efavirenz is also used in combination with other antiretroviral agents as part of an expanded postexposure prophylaxis regimen to prevent HIV transmission for those exposed to materials associated with a high risk for HIV transmission.

Lamivudine is a reverse transcriptase inhibitor used alone or in combination with other classes of anti-human immunodeficiency virus (HIV) drugs in the treatment of HIV infection. This molecule has two stereo-centers, thus giving rise to four stereoisomers: (+/-)-cis-lamivudine and (+/-)-trans-lamivudine. The latter is considered to be impurity of the pharmaceutically active isomer, (-)-cis-lamivudine.

Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Zidovudine is phosphorylated to active metabolites that compete for incorporation into viral DNA. They inhibit the HIV reverse transcriptase enzyme competitively and act as a chain terminator of DNA synthesis. The lack of a 3'-OH group in the incorporated nucleoside analogue prevents the formation of the 5' to 3' phosphodiester linkage essential for DNA chain elongation, and therefore, the viral DNA growth is terminated. Zidovudine, a structural analog of thymidine, is a prodrug that must be phosphorylated to its active 5′-triphosphate metabolite, zidovudine triphosphate (ZDV-TP). It inhibits the activity of HIV-1 reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue. It competes with the natural substrate dGTP and incorporates itself into viral DNA. It is also a weak inhibitor of cellular DNA polymerase α and γ. Zidovudine is used in combination with other antiretroviral agents for the treatment of human immunovirus (HIV) infections. Zidovudine is marketed as Retrovir.

Trifluridine (also called trifluorothymidine or TFT) is an anti-herpesvirus antiviral drug, used primarily on the eye. It was sold under the trade name, Viroptic, by Glaxo Wellcome, now merged into GlaxoSmithKline. It is a nucleoside analogue, a modified form of deoxyuridine, similar enough to be incorporated into viral DNA replication, but the -CF3 group added to the uracil component blocks base pairing, thus interfering with DNA replication. It is a component of the experimental anti-cancer drug TAS-102. Trifluridine is a fluorinated pyrimidine nucleoside with in vitro and in vivo activity against herpes simplex virus, types 1 and 2 and vaccinia virus. Some strains of adenovirus are also inhibited in vitro. VIROPTIC is also effective in the treatment of epithelial keratitis that has not responded clinically to the topical administration of idoxuridine or when ocular toxicity or hypersensitivity to idoxuridine has occurred. In a smaller number of patients found to be resistant to topical vidarabine, VIROPTIC was also effective. The mechanism of action of trifluridine has not been fully determined, but appears to involve the inhibition of viral replication. Trifluridine does this by incorporating into viral DNA during replication, which leads to the formation of defective proteins and an increased mutation rate.

ABX-464 is being developed by Abivax, in collaboration with the Cuban Center for Genetic Engineering and Biotechnology (CIGB), for the treatment of HIV. ABX-464, has demonstrated the potential to address indications in two disease areas: treatment of inflammation in ulcerative colitis and reduction of the viral reservoir in HIV. ABX-464 is an oral, first-in-class, small molecule that has demonstrated safety and profound anti-inflammatory activity in preclinical trials and in a completed Phase 2a proof-of-concept study to treat lesions in ulcerative colitis. It also inhibited HIV replication through an entirely new mechanism of action, and has completed three Phase 2a clinical trials. ABX-464 inhibits HIV-1 replication in stimulated peripheral blood mononuclear cells (PBMCs) with an IC50 ranging between 0.1 uM and 0.5 uM. In two Phase 2a clinical trials, ABX464-004 and ABX464-005, ABX-464 demonstrated up to 50% reduction of HIV-DNA in peripheral blood mononuclear cells after 28 days of combination treatment with anti-retroviral therapy. This unique mode of action and the preclinical data to-date suggest that ABX-464 has the potential to: Reduce or eliminate the viral reservoirs in patients with HIV Induce long term control of the viral load, Prevent the emergence of HIV mutants that are resistant to treatment after six months of treatment in vitro Be less frequently administered. When evaluated in a Phase 2a Proof-of-Concept study, ABX464-101, ABX-464 demonstrated both safety and statistically significant efficacy based on both clinical and endoscopic endpoints with 35% of the patients achieving a clinical remission (placebo: 11%) and 50% of patients achieving mucosal healing (placebo: 11%), (p=0.034) Because of its ability to greatly upregulate production of a unique RNA splicing product and anti-inflammatory agent, miR-124, ABX-464’s mechanism of action is unique and has shown promise in clinical trials in its ability to bring patients to remission and heal inflammatory lesions in ulcerative colitis.