Adefovir dipivoxil (GS 0840) is a dipivoxil formulation of adefovir, a nucleoside reverse transcriptase inhibitor analog of adenosine with activity against hepatitis B virus (HBV), herpes virus, and human immunodeficiency virus (HIV).

Compared to the placebo control group with 5.3 log10 GE/mL, Adefovir Dipivoxil significantly reduced serum HBV DNA levels in transgenic mice to 3.5 log10 genome equivalents (GE) per mL, indicating a marked suppression of the hepatitis B virus. In the liver, Adefovir Dipivoxil's antiviral activity peaked on day 10, achieving hepatitis B virus inhibition endpoints at a dose of 1.0 mg/kg/day. Furthermore, Adefovir Dipivoxil decreased liver HBV DNA to <0.1 picograms of hepatitis B virus per total DNA (picograms/mg) in each transgenic mouse.

In the duck HBV (DHBV) model, Adefovir dipivoxil, when used in combination with other nucleoside analogs (Lamivudine, Entecavir, Emtricitabine [FTC], and Telbivudine [L-dT]), exhibits superior antiviral effects compared to monotherapy. Adefovir dipivoxil effectively inhibits viral CCC DNA both in vitro and in vivo within the same model. Notably, Adefovir retains significant anti-HBV activity soon after being introduced to cells. Its use in conjunction with Lamivudine, FTC, or L-dT demonstrates cumulative effects, while synergy is observed when combined with Entecavir or Tenofovir. Additionally, Adefovir dipivoxil suppresses the activity of the polymerase by inhibiting the transcription of the pre-genomic RNA. The dosage of Adefovir dipivoxil is correlated with its ability to suppress the release of the virus in culture supernatants and the synthesis of viral DNA within cells.