BRII-B (02137) announced the 24-week post-treatment follow-up results from Cohort 4 of its ongoing ENSURE Phase II study. The latest findings were presented at the American Association for the Study of Liver Diseases (AASLD) Liver Meeting® held in Washington, D.C., from November 7–11, 2025, and simultaneously published in *Nature Medicine*.

The ENSURE study (NCT05970289) is a multicenter, open-label Phase II trial conducted in the Asia-Pacific region. Cohort 4 evaluated an innovative sequential combination therapy strategy for hepatitis B (HBV), utilizing the company’s therapeutic vaccine BRII-179 to activate and enrich patient immune responses, thereby improving their potential for functional cure.

Participants in this cohort had previously received nine doses of elebsiran combined with BRII-179 in the BRII-179-835-001 Phase II study (NCT04749368) and were subsequently treated with a 48-week regimen of elebsiran and PEG-IFNα. Based on peak anti-HBs antibody levels (≥10 IU/L or <10 IU/L) from prior studies, participants were categorized as BRII-179 anti-HBs responders or non-responders.

The newly released data demonstrated sustained benefits in hepatitis B surface antigen (HBsAg) clearance among BRII-179 responders during follow-up. At the end of treatment (EOT), 58% (11/19) of anti-HBs responders achieved HBsAg clearance, compared to only 17% (2/12) in non-responders. At 24 weeks post-treatment, 42% (8/19) of responders maintained HBsAg clearance, while only 8% (1/12) of non-responders did so.

Notably, among anti-HBs responders who sustained HBsAg clearance at 24 weeks post-EOT, 50% (4/8) had baseline HBsAg levels between 1,514–3,086 IU/mL, indicating that BRII-179 can induce immune responses even in patients with higher baseline HBsAg levels. This supports BRII-179’s potential to improve functional cure outcomes and expand its applicability across diverse patient populations.

To further clarify BRII-179’s role in HBV treatment and optimize combination therapies for pivotal studies, the company is conducting two additional Phase IIb trials. The ENRICH study aims to assess BRII-179’s ability to induce HBV-specific immunity and identify patients more likely to achieve functional cure. The ENHANCE study consists of two parts: evaluating a 48-week concurrent triple therapy (BRII-179, elebsiran, and PEG-IFNα) and exploring a sequential approach—24 weeks of BRII-179 and elebsiran followed by 24 weeks of triple therapy, compared to a 48-week PEG-IFNα control group. Both studies have completed patient enrollment, with EOT data expected in 2026.

Dr. David Margolis, Chief Medical Officer of BRII-B, stated, "We are encouraged that the difference in HBsAg clearance rates at EOT was maintained through the 24-week follow-up. These results highlight BRII-179’s potential to achieve faster, more durable HBsAg clearance and possibly shorten PEG-IFNα treatment duration. We look forward to confirming these findings in ongoing confirmatory studies."