BARACLUDE® is the tradename for entecavir, a guanosine nucleoside analogue with selective activity against hepatitis B virus (HBV). It inhibits all three steps in the viral replication process. By competing with the natural substrate deoxyguanosine triphosphate, entecavir functionally inhibits all three activities of the HBV polymerase (reverse transcriptase, rt): (1) base priming, (2) reverse transcription of the negative strand from the pregenomic messenger RNA, and (3) synthesis of the positive strand of HBV DNA. Upon activation by kinases, the drug can be incorporated into the DNA which has the ultimate effect of inhibiting the HBV polymerase activity. Entecavir is used for the treatment of chronic hepatitis B virus infection in adults with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease.

The potential antiviral effect of adefovir, an acyclic nucleoside phosphonate analog of 2′-deoxyadenosine monophosphate, was first studied by Holý and De Clercq in 1980s. Adefovir is an acyclic nucleotide analog of adenosine monophosphate which is phosphorylated to the active metabolite adefovir diphosphate by cellular kinases. Adefovir diphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate and by causing DNA chain termination after its incorporation into viral DNA. Oral adefovir dipivoxil is effective and generally well tolerated in HBeAg-positive and -negative patients chronically infected with wild-type or lamivudine-resistant HBV.

CMX157 is a lipid (1-0-hexadecyloxypropyl) conjugate of the acyclic nucleotide analog tenofovir (TFV) with activity against both wild-type and antiretroviral drug-resistant HIV strains, including multidrug nucleoside/nucleotide analog-resistant viruses. CMX157 was designed to mimic lysophosphatidylcholine to take advantage of natural lipid uptake pathways and to achieve high intracellular concentrations of the active antiviral, with the aim of increasing the effectiveness of TFV against wild-type and mutant HIV. CMX157 demonstrated potential to effectively suppress replication of multiNRTI-resistant (MNR) HIV that cannot be treated with any currently available NRTIs, including TDF. It is in phase II clinical trial for HIV infections in USA and phase Ib portion of the phase I/II trial for Hepatitis B in Thailand (PO).