Entecavir is a cyclopentyl guanosine analog launched for the once-daily oral treatment of chronic hepatitis B virus (HBV) infection, and it is the third nucleoside or nucleotide analog to be marketed for this indication. Lamivudine, a deoxythiacytosine analog, and adefovir dipivoxil, a nucleotide analog, have been marketed since 1998 and 2002, respectively. Entecavir and adefovir are specifically indicated for HBV, whereas lamivudine is indicated for both HBV and HIV infections.
