Arbutus Biopharma Corporation announced that preliminary data from its on-going Phase 2a clinical trial evaluating the safety, tolerability and antiviral activity of the combination of AB-729, the Company's lead RNAi therapeutic, and pegylated interferon alfa-2a (IFN) in patients with chronic hepatitis B virus (cHBV) was presented at the European Association for the Study of the Liver (EASL) Congress. The preliminary data suggests that the addition of IFN to AB-729 treatment was generally well tolerated and appears to result in continued HBsAg declines in some patients. Forty-three virally suppressed, HBeAg negative cHBV patients were enrolled in the clinical trial and received a lead-in of AB- 729 (60mg every 8 weeks) plus nucleos(t)ide analog (NA) therapy for 24 weeks followed by 12 or 24 weeks of IFN with or without additional AB-729 doses.

The preliminary data showed the following: The mean HBsAg decline from baseline during the lead-in phase was 1.6 log10 at week 24 of treatment which is, comparable to what was previously seen in other clinical trials with AB-729. HBsAg levels <100 IU/mL were noted during the treatment period in 93% (38 of 41 randomized) of the patients. Four patients have reached HBsAg below the lower limit of quantitation (LLOQ) during IFN treatment, however, none of the patients have achieved sustained seroclearance to date.

AB-729 treatment alone or in combination with IFN was generally well tolerated. There were no serious adverse events (SAEs), discontinuations or AB-729 treatment discontinuations. IFN-related treatment emergent adverse events (TEAEs) were consistent with the known safety profile.

Five patients required IFN dose modifications due to laboratory abnormalities. The clinical trial remains ongoing with most patients still in the early IFN treatment period continuing to be followed for on- treatment responses. After completion of the IFN treatment period, patients are followed for an additional 24 weeks on NA therapy alone, then assessed for NA discontinuation.

Three patients have been evaluated to stop NA treatment to date, with one meeting the protocol-defined criteria to stop NA treatment. AB-729 is an RNA interference (RNAi) therapeutic specifically designed to reduce all HBV viral proteins and antigens, including hepatitis B surface antigen, which is thought to be a key prerequisite to enable reawakening of a patient's immune system to respond to the virus. AB-729 targets hepatocytes using Arbutus' novel covalently conjugated N- Acetylgalactosamine (GalNAc) delivery technology that enables subcutaneous delivery.

Clinical data generated thus far has while providing meaningful reductions in hepatitis B surface antigen and hepatitis B DNA. AB-729 is currently in multiple Phase 2a clinical trials. About HBV Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV).

HBV can cause chronic infection which leads to a higher risk of death from cirrhosis and liver cancer. Chronic HBV infection represents a significant unmet medical need. The World Health Organization estimates that over 290 million people worldwide suffer from chronic HBV infection, while other estimates indicate that approximately 2.4 million people in the United States suffer from chronic HBV infection.

Approximately 820,000 people die every year from complications related to chronic HBV infection despite the availability of effective vaccines and current treatment options.