Arbutus Biopharma and Barinthus Bio Present Preliminary Data from Phase 2a Clinical Trial Combining Imdusiran with VTP-300 at AASLD - The Liver Meeting®

The combination of imdusiran and VTP-300 provides a meaningful reduction of HBsAg levels that are maintained well below baseline

Preliminary data in subset of patients given imdusiran and then VTP-300 show early signs of immune activation

WARMINSTER, Pa. and OXFORD, United Kingdom, Nov. 09, 2023 (GLOBE NEWSWIRE) -- Arbutus Biopharma Corporation (Nasdaq: ABUS), a clinical-stage biopharmaceutical company leveraging its extensive virology expertise to develop a cure for people with chronic hepatitis B virus (cHBV) infection, and Barinthus Biotherapeutics plc (Nasdaq: BRNS), formerly Vaccitech plc, a clinical-stage biopharmaceutical company developing novel T cell immunotherapeutic candidates designed to guide the immune system to overcome chronic infectious diseases, autoimmunity and cancer, today announced a late breaking poster presentation at The American Association for the Study of Liver Diseases (AASLD) – The Liver Meeting® 2023. The poster contains preliminary data from the Phase 2a clinical trial (AB-729-202) combining Arbutus’ RNAi therapeutic, imdusiran (AB-729), with Barinthus Bio's T-cell stimulating immunotherapeutic, VTP-300, and standard-of-care nucleos(t)ide analogue (NA) therapy.

Professor Man-Fung Yuen, D.Sc., M.D., Ph.D., Chief of the Division of Gastroenterology and Hepatology, University of Hong Kong, and a lead investigator of this Phase 2a clinical trial, stated, “These preliminary data are very encouraging and we look forward to additional follow-up of these patients which will provide insight into the possibility of a functional cure with this combination treatment regimen. It is well accepted that a combination therapy that can both reduce HBV surface antigen and stimulate an HBV-specific host immune response will be needed to provide a functional cure for patients with chronic HBV. These promising initial data show that the combination of imdusiran followed by VTP-300 reduces surface antigen from baseline and, importantly, the reduced levels are maintained compared to placebo controls. Although the patient numbers are small and the data are early to see the expected clinical effect of VTP-300 on surface antigen, it is impressive to see that some patients have more robust immune activation post-VTP-300 treatment compared to controls.”

Clinical trial AB-729-202 enrolled 40 non-cirrhotic, virally suppressed cHBV patients that were on stable NA therapy. The patients initially received imdusiran (60mg every 8 weeks) for 24 weeks and were then randomized to receive either VTP-300 or placebo at week 26 and 30 (and conditionally at week 38 if they experienced a >0.5 log10 decline in HBsAg between weeks 26 and 34), in addition to ongoing NA therapy. The preliminary data include a subset of patients that received the two dose VTP-300 regimen (28/40 patients) and available follow-up data to week 48 (12/40 patients) and showed the following:

• Robust reductions of HBsAg were seen during the imdusiran treatment period (-1.86 log10 mean reduction from baseline after 24 weeks of treatment). This decline in HBsAg is comparable to the declines seen with imdusiran in other clinical trials conducted to date.
• 97% of the imdusiran treated patients (33/34) had HBsAg