Study Comparing the Safety of Switching From Lamivudine to Adefovir Dipivoxil Versus Overlapping Lamivudine and Adefovir Before Adefovir Dipivoxil Monotherapy in Patients With Chronic Hepatitis B

Chronic HBV infection is an important worldwide cause of morbidity, mortality and source of
potential new infections. There are an estimated 350 million carriers of HBV in the world.
In China, Southeast Asia and sub-Saharan Africa, as many as 10-15% of the population are
chronically infected. In North America and Northern Europe, infection and carrier rates are
much lower, usually below 1%. Intermediate carrier rates of 1-5% are found in Southern
Europe (e.g., Italy, Greece and Spain), parts of South and Central America, the Middle East
and Japan. Persistent infection develops in over 90% of perinatally infected children and
in 3-10% of people who become infected after the age of 6 years. Worldwide, it has been
estimated that more than one million people die annually due to HBV-related end stage
diseases such as cirrhosis and hepatocellular carcinoma.

The goal of antiviral therapy for hepatitis B is to reduce a patient’s risks for progressive
liver disease through prolonged suppression or eradication of HBV infection and to arrest or
ameliorate HBV-related liver damage.

Inclusion Criteria:

- Males and females ≥ 18 years of age with chronic hepatitis B

- Hepatitis B surface antigen (HBsAg)(+) for a minimum of 6 months prior to entry

- Hepatitis B envelope antigen (HBeAg)(+) or (-) at baseline

- Patients having previously received LAM for at least 24 weeks

- Patients with compensated liver function (Child-Pugh score ≤ 6)

Exclusion Criteria:

- Any serious or active medical or psychiatric illness which, in the opinion of the
investigator, would interfere with patient treatment, assessment or compliance with
the protocol.

- Received immunoglobulins, interferon or other immune or cytokine-based therapies with
possible activity in hepatitis B disease within 6 months prior to study screening.

- Organ or bone marrow transplant recipients.

- Evidence of active liver disease due to other causes (e.g., Wilson’s disease,
hemochromatosis, autoimmune hepatitis, hepatitis C or hepatitis D co-infection)

- Patients taking parenteral (intravenous or intramuscular or subcutaneous) or oral
steroids, immuno-suppressant therapies or chemotherapeutic agents within 2 months of
study screening or expected to receive these agents during the course of the study.

- Previous participation in an investigational trial involving administration of any
investigational compound within 2 months prior to the study screening or those who
received anti-HBV therapy other than lamivudine within the previous 3 months (e.g.
anabolic steroids, ketaconazole, itraconazole, isoniazid, rifampin, rifabutin,
simvastatin, lovastatin)

- Clinically relevant alcohol or drug use or history of alcohol or drug use considered
by the investigator to be sufficient to hinder compliance with treatment, follow up
procedures or evaluation of adverse events

- Lactating females or females with a positive serum pregnancy test.

- Females of childbearing potential (post-puberty) unwilling or unable to have
pregnancy testing at any study visit

- Therapy with nephrotoxic drugs (e.g. aminoglycosides, amphotericin B, vancomycin,
cidofovir, foscarnet, cisplatin pentamidine, tacrolimus, cyclosporine) or competitors
of renal excretion (e.g. probenecid) within 2 months prior to study screening or the
expectation that subject will receive these during the course of the study.

- The use of antiviral therapy with agents demonstrating potential anti-HBV activity
other than lamivudine within the previous 3 months (e.g. famciclovir, lobucavir,
emtricitabine, DAPD, L-FMAU, entecavir, ganciclovir or others).

- History of hypersensitivity to nucleoside and/or nucleotide analogues.

- Clinical, ultrasonographic or radiologic evidence of hepatic mass suggestive of
hepatocellular carcinoma.

- Serum alphafetoprotein (AFP) > 50 ng/mL at the first screening visit. However, if the
AFP level is > 50 ng/mL at the first screening visit, but has remained stable or
decreased over the 6 months preceding the first screening visit, and if there is no
radiologic or ultrasonic evidence of hepatic mass(es) suggestive of hepatocellular
carcinoma, the patient will be allowed to enroll.

- Inability to comply with study requirements.