Current pharmacotherapy for the treatment of chronic hepatitis B.

The virological profile of infection with the hepatitis B virus (HBV) is changing in many parts of the world from the classical hepatitis B e antigen (HBeAg)-positive serological pattern to a HBeAg-negative pattern, linked to the replacement of wild-type HBV by HBV variants with mutations in the core-promoter and in the precore region that prevent the secretion of HBeAg. The wild-type HBV disease is characterised by steady levels of alanine aminotransferase (ALT) and high HBV-DNA levels, responding relatively well to IFN treatment (3 - 5 MU/day or 10 MU every other day for 16 weeks), which induces anti-HBe seroconversion and normalises ALT levels in approximately 30% of the adults, with a minimal risk of relapse. Pegylated-IFN appears to have superior efficacy over conventional IFN-alpha. Mutant-type disease (anti-HBe-positive/HBeAg-negative) is less responsive to IFN given for 6 - 12 months. This has led to the use of novel nucleoside analogues, of which the prototype is lamivudine. The response to lamivudine therapy shares with IFN a rapid decline in ALT accompanied by an improvement in histology; at variance with IFN, in HBeAg-positive chronic hepatitis B (CHB) there is delayed seroconversion to anti-HBe which accumulates over time, the switch to anti-HBs is more rare and in the long-term, the activity of the drug is abolished by the emergence of viral mutations (YMDD-motif mutants) that may rekindle the disease. The combination of IFN plus lamivudine may be more efficacious than IFN or lamivudine monotherapy. Lamivudine therapy needs to be prolonged in HBeAg-negative CHB. Short-term lamivudine-therapy is highly efficacious in preventing HBV reinfection in liver transplants. Recent data suggest that long-term IFN therapy (24 months) may achieve a response in 30% of HBeAg-negative patients. The advent of adefovir, an analogue of adenosine monophosphate, may provide a safer alternative to lamivudine in the control of HBV disease; the drug is well-tolerated and treatment raises drug-resistant mutants in < 2% of the patients over 2 years of therapy. Adefovir provides rescue therapy against YMDD mutants raised by lamivudine therapy.