Entecavir inhibits HBV polymerase base priming, reverse transcription of the negative strand from the pregenomic messenger RNA, and synthesis of positive-strand HBV DNA. It is approximately 30-fold more potent than lamivudine in vitro. Entecavir is a nucleoside analog that works by inhibiting the hepatitis B virus (HBV) replication process at three stages Base priming : Entecavir competes with deoxyguanosine triphosphate (dGTP) for uptake by the HBV DNA polymerase Reverse transcription : Entecavir inhibits the reverse transcription of the negative strand of DNA from the pre-genomic messenger RNA Positive strand synthesis : Entecavir inhibits the synthesis of the positive strand of HBV DNA