Elvucitabine (ACH-126443 or beta-L-Fd4C) is a reverse transcriptase inhibitor exerting antiviral properties. Elvucitabine, an L-cytosine nucleoside analog, is intracellularly phosphorylated to its active 5′-triphosphate metabolite, which has an intracellular half-life of at least 20 hours. Elvucitabine triphosphate inhibits the activity of HIV reverse transcriptase by competing with natural substrates and by causing DNA chain termination after incorporation into viral DNA. Elvucitabine has also demonstrated in vitro and in vivo activity against HBV. Achillion, under license from Vion is developing elvucitabine for the potential treatment of HIV and hepatitis B virus (HBV) infection.

Disoxaril is the antipicornavirus drug. It is an isoxazole heterocyclic compound and a member of the antiviral series commonly referred to as WIN compounds. Disoxaril inhibits enterovirus replication by binding to the hydrophobic pocket within the VP1 coat protein, thus stabilizing the virion and blocking its uncoating. The amino acid sequence of a large VP1 196-258 peptide (disoxaril-binding region) of CVB1/RESISTANT was significantly different from that of the CVB1/SOF (sensitive). Crucially important changes in CVB1/RES were two point mutations, M213H and F237L, both in the ligand-binding pocket. Treatment with disoxaril in newborn mice infected with Coxsackie B1 virus, for 10 days post virus inoculation decreased the virus titer in the mouse brain till day 7.

Omaciclovir (previously known as H2G), a cyclic guanosine analog that is structurally similar to acyclovir and was in clinical development for the treatment of herpesvirus infections. This drug acted against varicella-zoster virus (VZV), by the formation of high concentrations of relatively stable H2G-triphosphate, which is a potent inhibitor of the viral DNA polymerases. However, further development of this drug was discontinued.

Fialuridine, or 1-(2-deoxy-2-fluoro-1-D-arabinofuranosyl)-5-iodouracil (FIAU) is a thymidine nucleoside analog with activity against various herpesviruses and hepatitis B virus (HBV) in vitro and in vivo. Herpes virus thymidine kinase considered to be a target of FIAU. In a Phase II study, fialuridine induced a severe toxic reaction in chronic hepatitis B patients characterized by hepatic failure, lactic acidosis, pancreatitis, neuropathy, and myopathy. These clinical manifestations led to the hypothesis that the toxicity of FIAU was mediated through mitochondrial dysfunction, possibly as a result of the inhibition of mitochondrial DNA polymerase gamma and/or incorporation of FIAU into mitochondrial DNA.

Radalbuvir (also known as GS-9669 ) is a Hepatitis C virus NS 5 protein inhibitor for the treatment of hepatitis C virus (HCV) infection developed by Gilead Sciences. Radalbuvir is a highly optimized thumb site II nonnucleoside inhibitor, with a binding affinity of 1.35 nM for the genotype (GT) 1b protein. It is a selective inhibitor of HCV RNA replication, with a mean 50% effective concentration of ≤ 11 nM in genotype 1 and 5 replicon assays, but lacks useful activity against genotypes 2 to 4. In preclinical Radalbuvir exhibited at least additive activity in combination with agents encompassing four other direct modes of action (NS3 protease, NS5A, NS5B via an alternative allosteric binding site, and NS5B nucleotide) as well as with alpha interferon or ribavirin in replicon assays. It exhibited high metabolic stability in vitro human liver microsomal assays, which, in combination with its pharmacokinetic profiles in rat, dog, and two monkey species, is predictive of good human pharmacokinetics. In clinical trials, Radalbuvir shows highly effective inhibition of wild-type HCV.

Ruzasvir (previously known as MK-8408) was developed as a nonstructural protein 5A (NS5A) inhibitor for the treatment of hepatitis C and hepatitis C infection. Ruzasvir successfully completed phase II clinical trial for combination therapy. The obtained results have shown that ruzasvir in combination with uprifosbuvir was highly effective and well-tolerated in participants infected with hepatitis C virus genotypes GT1, GT2, GT4, GT5, and GT6, with a lower efficacy in GT3-infected persons.

Lobucavir is a new anti-cytomegalovirus infection agent, manufactered by Bristol Myers Squibb, Inc. Lobucavir is a cyclobutyl analog of guanine with broad spectrum antiviral activity against most herpes viruses and Hepatitis B. Lobucavir was shown to inhibit herpes simplex virus (HSV) DNA polymerase after phosphorylation by the HSV thymidine kinase. The drug was well tolerated with few side effects. Lobucavir had been in phase III clinical trial for the treatment of Hepatitis B, Herpes simplex virus infections and in phase II for the treatment of Cytomegalovirus infections. All these studies were discontinued.