Taribavirin, an oral prodrug of ribavirin that was developed as nucleoside antimetabolite, which interferes with duplication of viral genetic material. Taribavirin was studied in phase III clinical trial for the treatment of chronic hepatitis C patients. However, this drug not yet approved for pharmaceutical use.

Vicriviroc or SCH 417690 is a potent and selective antagonist of the CCR5 receptor. vicriviroc binds specifically to the CCR5 receptor and prevents infection of target cells by CCR5-tropic HIV-1 isolates. In antiviral assays, vicriviroc showed potent, broad-spectrum activity against genetically diverse and drug-resistant HIV-1 isolates and was consistently more active than SCH-C in inhibiting viral replication. This compound demonstrated synergistic anti-HIV activity in combination with drugs from all other classes of approved antiretrovirals. Competition binding assays revealed that vicriviroc binds with higher affinity to CCR5 than SCH-C. Functional assays, including inhibition of calcium flux, guanosine 5'-[35S]triphosphate exchange, and chemotaxis, confirmed that vicriviroc acts as a receptor antagonist by inhibiting signaling of CCR5 by chemokines. Finally, vicriviroc demonstrated diminished affinity for the human ether a-go-go related gene transcript ion channel compared to SCH-C, suggesting a reduced potential for cardiac effects. Vicriviroc represented a promising new candidate for the treatment of HIV-1 infection. Vicriviroc for HIV treatment was previously in Phase III studies but has since been discontinued.

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.

Mimbane was developed by Parke-Davis as an analgesic. Information about the current use of the drug is not available.

Aplaviroc (GW873140) is a small-molecule noncompetitive allosteric CCR5 antagonist or HIV entry inhibitor (EI) that binds specifically to human CCR5 and exhibits potent anti-HIV activity in vitro in the nanomolar or subnanomolar range. Aplaviroc has exhibited potent in vivo antiviral activity (1.66 log decrease in viral load at nadir) following 10 days of monotherapy. In vitro studies of antiviral activity demonstrate that aplaviroc is active against HIV isolates from a variety of clades as well as those resistant to current HIV therapies targeting RT, PR, and gp41. However, GlaxoSmithKline has decided to terminate Phase III trials of aplaviroc after encountering additional cases of liver damage in patients taking the drug.

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.

Torcitabine is the beta-L-enantiomer of the natural nucleoside D-cytidine. The drug was under development as an antiviral agent for the treatment of chronic hepatitis B virus infection. Torcitabine has poor oral bioavailability, but its 3’,5’-derivative ester (val-L-dC) and the 3’-monovaline ester, valtorcitabine dihydrochloride, have excellent oral bioavailability and consequently the torcitabine prodrug, valtorcitabine, has replaced torcitabine in clinical development. Torcitabine is active against hepadnaviruses, specifically human hepatitis B virus (HBV), duck hepatitis virus (DHBV) and woodchuck hepatitis virus (WHV). Torcitabine triphosphate is a selective inhibitor of the polymerase enzyme of HBV.

Somantadine, an adamantane derivative, is an antiviral agent. Somantadine was synthesized by Pennwalt and has been undergoing tests for the treatment of herpes virus for nearly five years.

Memotine (UK2371)is an isoquinoline antiviral compound. In vitro, it is active against myxoviruses and paramyxoviruses. It is not active against rhinoviruses. Memotine given orally reduces the antibody response and the incidence of clinical reactions.

Famotine, 1 -(p-chlorophenoxymethyl)-3,4-dihydroisoquinoline (UK 2054), is an antiviral compound.