The purpose of this study is to compare the use of HepeX-B versus HBIg, two anti-viral drugs, in patients who have received liver transplants due to liver failure caused by Hepatitis B infection. Patients will be evaluated over a 6 month to 1.5 year period to evaluate whether or not the drugs prevent the Hepatitis B virus from infecting the new liver.

Inclusion Criteria:

• Male and female patients who are 18 years of age or older,
• Patients who are at least 6 months post first orthotopic liver transplantation (living or cadaveric donor) for treatment of end-stage liver disease due to HBV infection,
• Patients who have received HBIg since transplantation and are on a stable regimen (i.e., same dose and frequency) for at least the 3 months immediately preceding study entry (Day 1),
• Patients who have received treatment with an inhibitor of HBV polymerase for at least the 3 months immediately preceding study entry (Day 1),
• Patients with undetectable HBsAg and HBV DNA concentrations on two consecutive tests at least 1 week apart during the screening period,
• Female patients who are of childbearing potential, and males whose partners are women of childbearing potential, are required to use adequate contraception, and
• Patients who are able to provide written informed consent.
• Patients who successfully complete the initial 20-week treatment in the core trial are eligible for the 52-week extension phase.

Exclusion Criteria:

• Women who are pregnant or breastfeeding,
• Patients who have received another organ transplant that requires immunosuppression,
• Patients who are co-infected with hepatitis delta virus (HDV), hepatitis C virus (HCV) and/or human immunodeficiency virus (HIV),
• Patients with clinical conditions or diseases, which, in the judgment of the investigator, would place the patient at undue risk, interfere with study participation, or confound the results of the study, and/or
• Patients who have participated in clinical studies in the 3 months prior to study entry.