Arbutus Presents Preliminary AB-729 and Pegylated Interferon Alfa-2a Combination Data at the EASL Congress 2023

Treatment was generally well tolerated with continued HBsAg declines in some patients

WARMINSTER, Pa., June 21, 2023 (GLOBE NEWSWIRE) -- Arbutus Biopharma Corporation (Nasdaq: ABUS) (“Arbutus” or the “Company”), a clinical-stage biopharmaceutical company leveraging its extensive virology expertise to develop novel therapeutics that target specific viral diseases, today 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 today 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.

William Collier, President and Chief Executive Officer of Arbutus, commented, “These data continue to support our strategy of utilizing AB-729 as a cornerstone in a combination therapeutic for patients with cHBV. In this trial, some patients that received 12 weeks or more of IFN after AB-729 treatment saw promising declines in surface antigen, which continues to reinforce our confidence in AB-729’s ability to effectively suppress HBsAg. While this is a small sample size and additional follow-up is needed, we believe that the combination of AB-729 and IFN is both safe and lowers surface antigen, which in turn, may allow the patient’s immune system to control the virus. We look forward to providing more data as patients continue to receive treatment.”

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.