Proof-of-concept Study Evaluating the Safety and Efficacy of EBP921 in Delta Hepatitis (HDV)

This is an open-label, phase 1b, proof-of-concept study to assess the safety and efficacy of
EBP921, a prenylation inhibitor, in subjects chronically infected with delta hepatitis.
Subjects will be randomized to receive one of two different doses of EBP921. Dosing will
occur over 28-days and during that time, evidence of antiviral response will be assessed by
frequent measurements of HDV-RNA via PCR assay. In addition, safety lab data will also be
collected along with surveillance monitoring of HBV activity.

Inclusion Criteria:

1. Men and women age 18 or older with the capacity to give written informed consent

2. Patients with compensated chronic HDV infection as indicated by presence of anti-HDV
in serum.

3. Liver biopsy should be performed within one-year of study screening and graded using
the Knodell scoring system.

4. Presence of HDV antigen in liver tissue or HDV-RNA in serum.

5. Active HBV replication will not exclude patients.

6. Previous therapy with standard alpha-interferon or peginterferon will not exclude
patients.

7. Patients who are HBV therapy-naïve or who previously received HBV antiviral therapy
will be eligible. Patients currently taking HBV antiviral therapy will e considered
on a case basis.

8. Female subjects of reproductive potential and female partners of male subjects should
be on two reliable forms of contraception from the start of the study until 60 days
from the end of EBP921 dosing.

Exclusion Criteria:

1. Severe neuropsychiatric disorders

2. History or clinical manifestations of significant metabolic, hematological,
pulmonary, ischemic heart disease, significant or unstable heart disease,
gastrointestinal, neurological, renal, urological, endocrine, ophthalmologic
disorders including severe retinopathy, or immune-mediated disease

3. Pregnant or breast-feeding patients or the inability to practice adequate
contraception during the conduct of the study

4. Underlying autoimmune/immune-deficiency disease (e.g., lupus, sarcoidosis, celiac
disease, HIV antibody positive, AIDS)

5. Chronic (> 4 weeks duration) diarrhea

6. Body weight > 128 kg and < 40 kg

7. Uncompensated cirrhosis

8. Absolute neutrophil count less than 1500 per cubic millimeter

9. Platelet count less than 90,000 per cubic millimeter

10. Evidence of concurrent HCV infection with positive serum HCVRNA

11. Evidence of hepatocellular carcinoma

12. Active substance abuse (alcohol, inhaled or injected drugs) within the past 12 months

13. Diagnosis of malignancy in the previous five years excluding superficial dermatologic
malignancies

14. Any experimental therapy in the previous 6 months prior to enrollment.

16. Patients with a history of multiple drug resistant HBV 17. Patients receiving
interferon therapy for any reason.