Study of EPI-003 in Select Nucleos(t)Ide Analogue-Treated, Chronic Hepatitis B Patients

Prior treatment

• Previous history or current diagnosis of significant liver fibrosis or cirrhosis
• Positive test result for HIV-1 or HIV-2 that suggests a concurrent infection at Screening.
• History of acute febrile illness, symptomatic viral, bacterial, or fungal infection within 1 week before Day 1.
• History of receiving HBV vaccine or other HBV-targeted therapeutic within the 6 months before Day 1.
• Previous treatment with an HBV-targeted treatment other than NAs within the 6 months before Day 1 or planned use during the study.
• Chronic treatment with immunosuppressants.
• Received any antiplatelet or antithrombotic therapy.
• Have received any other IP within 30 days or 5 half-lives of Day 1.
• Have received any vaccination within 14 days prior to Day 1 or vaccination planned for 3 months following administration of IP.
• Received any medications or other treatments that may adversely affect the immune system.
• Significant drug abuse/addiction within 3 months of Screening.

Other illness

• Evidence or history of liver disease of non-HBV aetiology.
• Immunodeficient or autoimmune conditions due to disease.
• History of anaphylaxis, hypersensitivity, or significant drug allergies.
• History of thrombophilia or history of a positive genetic test for Factor V Leiden and/or prothrombin 20210.
• Known or suspected intolerance or hypersensitivity to the IP components.
• Any safety concern or personal condition that is inappropriate for study participation per the Investigator's judgement.

Lab values

• Participants with serum alpha-fetoprotein (AFP) ≥ 200 ng/mL at Screening.
• Any of the laboratory values at Screening (Screening laboratory tests may be repeated once for values thought to be erroneous OR not clinically significant as per the PI):
• Any history of unexplained blackouts, fainting episodes, significant arrythmias, clinically significant abnormality of ECG, marked QT abnormalities, or any known risk factors for Torsade de Points

Other

• Liver ultrasound or other imaging with findings suggestive of HCC at any time.
• Excess alcohol consumption within 3 months of Screening.

• Aged 18 to 65 years (inclusive) at the time of signing the informed consent.
• Body mass index (BMI) ≥ 18 kg/m2 and ≤ 35 kg/m2 at Screening, and body weight of ≤ 120 kg.
• Chronic HBV infection for ≥ 6 months prior to Screening (eg, positive for serum HBsAg, HBV DNA, HBeAg for ≥ 6 months ) or serum immunoglobulin M (IgM) anti-HBc (hepatitis B core antibody) negative at Screening; AND Baseline HBsAg positive at Screening.
• Has received treatment with a NA (entecavir, tenofovir disoproxil fumarate or tenofovir alafenamide) as a stable dose for ≥ 6 months before Screening and plans to continue at the same dose level for the duration of the study. Participants may be on other NAs but require Sponsor approval before enrolment.
• HBV DNA \< LLOQ (according to local guidelines) for ≥ 6 months and at Screening
• Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2 × upper limit of normal (ULN) at Screening.
• Able and willing to attend the necessary visits to the study site.
• Able and willing to provide written informed consent after the nature of the study has been explained and prior to the commencement of any study procedures.