Pharmacotherapy of Chronic Hepatitis B with Entecavir

Actually three nucleotide/nucleoside analogues are used for chronic hepatitis B: lamivudine, adefovir dipivoxil, entecavir and telbivudine. Lamivudine and adefovir are advantageous for oral administration and safety, but they induce a sustained response after withdrawal of therapy in only a minority of patients. Telbivudine is a new drug and further studies are need to evaluate its real efficacy. Entecavir, a cyclopentyl guanosine analog, is a potent inhibitor of HBV-DNA polymerase and it inhibits both priming and elongation steps of viral DNA replication. In phase II and III clinical trials, entecavir was found to be superior to lamivudine for all primary endpoints evaluated in both nucleoside-naive and lamivudine-resistant patients and it was effective in both HBeAg-positive and HBeAg-negative nucleoside-naive patients. Only one trial has evidenced cases of viral resistance to entecavir. The approved dosage in treatment-naive patients is 0.5 mg/day orally, while in patients who have failed lamivudine therapy or are known to harbour lamivudine-resistant mutants, the approved dosage is 1.0 mg/day.