Antiviral potency significantly differs among various antiviral agentsEntecavir and tenofovir disoproxil fumarate are equally recommendedas first-line treatments for patients with chronic hepatitis B (CHB). However, it is unclear whether treatment with these drugs is associated with equivalent clinical outcomes,especially impacts the risk of HCC recurrence. Entecavir and tenofovir disoproxil fumarate have comparable efficacy in achieving surrogate end points, including virologic response,but they do by different mechanisms .

Entecavir, a guanosine nucleoside analogue with activity against HBV reverse transcriptase (rt),is efficiently phosphorylated to the active triphosphate form, which has an intracellular half-life of 15 hours. By competing with the natural substrate deoxyguanosine triphosphate, entecavir triphosphate functionally inhibits all three activities of the HBV reverse transcriptase: (1) basepriming, (2) reverse transcription of the negative strand from the pregenomic messenger RNA,and (3) synthesis of the positive strand of HBV DNA.

Tenofovir fumarate is a cyclic nucleoside phosphine diester structural analog of adenosine monophosphate. Tenofovir disoproxil fumarate first needs to be converted to tenofovir by hydrolysis of the diester, followed by phosphorylation of cellular enzymes to form tenofovir diphosphate. Tenofovir diphosphate competes with the natural substrate 5'-deoxyadenosine triphosphate for its involvement in the synthesis of viral DNA, which, after entering the viral DNA strand, can cause DNA elongation to be blocked due to its lack of 3'-OH groups,thereby blocking the replication of the virus. Tenofovir diphosphate is a weak inhibitor of mammalian DNA polymerase alpha, beta and mitochondrial DNA polymerase gamma.