Three drugs have been approved by the Food and Drug Administration (FDA) for treatment of chronic HBV: interferon-α (IFN-α), lamivudine, and adefovir dipivoxil. Only one-third of chronic HBV patients develop a sustained response to IFN-α treatment, and adverse effects are common [ref 2]. Use of the newer orally-administered nucleoside analogues (lamivudine or adefovir dipivoxil) typically causes rapid initial clearance of virus and is associated with fewer adverse effects; however, seroconversion rates are low, and long-term therapy with lamivudine (required for sustained responses) frequently results in resistance [ref 2]. Adefovir dipivoxil has, so far, not shown the high rate of resistance observed with lamivudine, but it is expected that resistance will eventually develop [ref 3]. In summary, major problems with currently approved therapy of HBV include expense, toxicity, and development of resistance.