 NAPs have been previously shown to clear serum hepatitis B virus surface antigen HBsAg both preclinically in duck HBV infected ducks and in human patients. REP 2139-Ca mediated HBsAg clearance acts synergistically with immunotherapeutic agent pegylated interferon-alpha 2a to restore host immunological control of HBV infection. REP 2165 is a version of REP 2139 which has been shown preclinically to retain antiviral activity with lower accumulation in the liver. 