[New treatment options in chronic hepatitis B].

To date, four different nucleoside/nucleotide analogues are available in the treatment of chronic hepatitis B (CHB): lamivudine, adefovir dipivoxil and entecavir; telbivudine, a deoxythymidine analogue that specifically inhibits polymerase-DNA of HBV, approved by the European Medicines Agency (EMEA), has recently become obtainable in Italy. Lamivudine, the first antiviral drug to be used in the treatment of chronic hepatitis B, shows an excellent bioavailability, a virtual absence of significant adverse drug reactions, and a high efficacy in reducing the viral load. Such good pharmacological features are not paralleled by a high genetic barrier. Adefovir dipivoxil, a nucleotide analogue, is considered an effective alternative option to lamivudine, due to the better genetic barrier (almost 30 percent of resistant mutants after 5 years of treatment). However, at the therapeutic approved doses (10 mg/die), adefovir demonstrates sub-optimal efficacy in suppressing viral replication. By contrast, it has proved highly effective against viral strains resistant to lamivudine. Entecavir, the nucleoside analogue most recently introduced in Italy, exhibits a substantial inhibition of viral replication and a high genetic barrier both in naive patients (< 1% of resistant mutants after three years), and in patients resistant to lamivudine treatment. Telbivudine appears a new, promising antiviral agent, characterised by a rapid and sustained virologic response, together with a good genetic barrier. Its excellent tolerability and safety profile (FDA Pregnancy Category B), specific mechanism of activity (no activity against HIV) and efficacy characteristics make telbivudine a first choice therapeutic option for treatment of patients affected by CHB.