Brii Biosciences Limited (Stock Code: 2137) reported 24-week post end of treatment (EOT) findings from Cohort 4 of its ongoing Phase 2 ENSURE study at the American Association for the Study of Liver Diseases conference (AASLD) 2025, with simultaneous publication in Nature Medicine. ENSURE (NCT05970289) is a multicenter, open-label trial in the Asia-Pacific region, investigating a sequential therapeutic approach for hepatitis B virus (HBV) built around the company’s therapeutic vaccine, BRII-179.

Cohort 4 enrolled participants previously treated with nine doses of elebsiran and BRII-179 in an earlier Phase 2 study, who received a 48-week combination of elebsiran and PEG-IFNα. Based on peak hepatitis B surface antibody (anti-HBs) levels in the prior study, these participants were categorized as responders (≥10 IU/L) or non-responders (<10 IU/L). At EOT, hepatitis B surface antigen (HBsAg) loss was achieved in 58% (11/19) of responders compared to 17% (2/12) of non-responders. After 24 weeks of follow-up, 42% (8/19) maintained HBsAg loss in the responder group versus 8% (1/12) in non-responders. Half of the responders with sustained HBsAg loss at 24 weeks had previously initiated therapy with baseline HBsAg levels between 1,514 and 3,086 IU/mL, suggesting that BRII-179 may elicit anti-HBs responses even in higher baseline antigen contexts. The combination of elebsiran and PEG-IFNα was generally safe and well-tolerated.

Two additional Phase 2b trials, ENRICH and ENHANCE, are underway to further assess BRII-179 in priming HBV-specific immunity, evaluate triple therapies using BRII-179, elebsiran, and PEG-IFNα, and optimize regimens for potential pivotal studies. Both trials are fully enrolled, with end-of-treatment data anticipated in 2026.

A cautionary statement from the company advises there is no guarantee that BRII-179 and elebsiran will ultimately be successfully developed or marketed. Shareholders and potential investors are advised to exercise caution and consult professional advice if in doubt.