- Final results from the ENSURE study demonstrate that the addition of elebsiran resulted in a higher functional cure rate compared with pegylated interferon alfa (PEG-IFNα) alone

- Data from Cohort 4 suggested that participants responding to prior BRII‑179 treatment achieved the most robust functional cure outcomes, further supporting its potential clinical benefit

- Data from an ENSURE translational study demonstrated that BRII‑179-induced epitope-mismatched CD4+ T cells and HBs‑specific B cell maturation were associated with enhanced HBsAg loss following curative treatment, offering additional insights into its potential mechanisms

DURHAM, N.C. and BEIJING, May 27, 2026 /PRNewswire/ -- Brii Biosciences Limited ("Brii Bio" or the "Company", stock code: 2137.HK), a biotechnology company developing therapies to improve patient health and choice across diseases with high unmet medical need, today announced end-of-study (EOS) data from Cohorts 1-4 of its Phase 2 ENSURE study at the European Association for the Study of the Liver (EASL) Congress 2026 in Barcelona, Spain.

The ENSURE study (NCT05970289) is a multicenter, open-label Phase 2 study in the Asia-Pacific region. Cohorts 1-3 were designed to evaluate the contribution of elebsiran, an investigational small interfering ribonucleic acid (siRNA), to the combination treatment with PEG-IFNα in participants with chronic hepatitis B virus (HBV) infection with baseline hepatitis B surface antigen (HBsAg) of 100-3,000 IU/mL.

Cohort 4 evaluated a novel sequential combination treatment strategy for HBV utilizing Brii Bio's therapeutic vaccine, BRII-179, to prime and enrich participants with a goal of improving responsiveness to curative therapies. Participants previously treated with 9 doses of BRII-179 and elebsiran in the prior Phase 2 study BRII-179-835-001 (NCT04749368) were enrolled and received 48 weeks of combination treatment with elebsiran and PEG-IFNα. These participants were categorized as BRII-179 anti-HBs responders or non-responders based on whether their peak hepatitis B surface antibody (anti-HBs) titers exceeded 10 IU/L during the prior study.  

All participants were maintained on nucleos(t)ide analogues (NAs) for an additional 24 weeks upon completion of PEG-IFNα + elebsiran treatment. Functional cure rates at the end of ENSURE study, defined as sustained HBsAg loss with undetectable HBV DNA for at least 24 weeks after stopping all treatment, including NAs, are presented. Final results demonstrated that the HBsAg loss benefit observed in the elebsiran and PEG-IFNα combination cohorts translated into a higher functional cure rate compared to the PEG-IFNα alone cohort. BRII-179-experienced participants achieved higher functional cure rates, particularly among anti-HBs responders, suggesting that BRII-179 may play an important role in achieving durable immunological control of HBV.  

Brii Bio is conducting two additional Phase 2b trials to further define the role of BRII-179 in the treatment of chronic HBV infection and to optimize combination regimens for pivotal studies. The ENRICH study is evaluating the role of BRII-179 in priming HBV-specific immunity and identifying immuno-responsive patients with a higher likelihood of achieving functional cure. The ENHANCE study consists of two parts: one evaluating concurrent triple combination therapy with BRII-179, elebsiran and PEG-IFNα for 48 weeks, and another evaluating a sequential regimen of BRII-179 and elebsiran for 24 weeks followed by triple combination therapy for 24 weeks. End-of-treatment (EOT) data from both studies are expected to be presented in 2026.

"We are encouraged by the consistency of the findings observed throughout the ENSURE study and believe these final results highlight the potential of BRII-179 and elebsiran in improving functional cure outcomes," said David Margolis, M.D., Chief Medical Officer of Brii Bio. "Together with upcoming data from our ongoing studies, these results provide important insights to guide the future development of our HBV functional cure program."

Details of the late-breaker poster presentation are as follows:

Title: Functional cure rate in chronic hepatitis B virus infected participants receiving elebsiran and pegylated interferon alfa: final results from the phase 2 ENSURE study

Session/Presentation Type: Late-breaker posters

Session Time: May 27, 08:30 - May 30, 16:00 (UTC+1)

Abstract Number/Identifier: LB26-5012/ LBP-040

Presenter: Grace Lai-Hung Wong, MBChB (CUHK), MD (CUHK), FRCP (Lond, Edin), FHKCP, FHKAM (Medicine), Professor of Gastroenterology and Hepatology at CUHK Medical Data Analytics Centre (MDAC) and Department of Medicine and Therapeutics in Hong Kong SAR, China

• At Week 72 (24 weeks post EOT), 19 of 20 participants who achieved HBsAg loss met NA discontinuation criteria and stopped NA for the additional 24-week follow-up; One participant remained HBeAg positive.
• In Cohorts 1-3, functional cure was achieved in 2/19 (10.5%) and 3/18 (16.7%) participants from the elebsiran 200 mg or 100 mg + PEG-IFNα cohorts, respectively, compared with 1/18 (5.6%) in the PEG-IFNα cohort. In Cohort 4, functional cure was achieved in 8/31 (25.8%) participants, including 7/19 (36.8%) among anti-HBs responders compared with 1/12 (8.3%) among non-responders.
• Although all participants achieving functional cure had a baseline HBsAg levels below 1,000 IU/mL in the ENSURE study, 4/7 (57.1%) of anti-HBs responders achieving functional cure had baseline HBsAg levels between 1,154 and 3,086 IU/mL at enrollment in the prior BRII-179-835-001 study.
• After NA discontinuation, no new treatment-related adverse events (TRAE) were reported. Most TRAEs resolved during the post EOT follow-up period.
• Participants achieving sustained HBsAg loss through combination therapy demonstrated favorable off-NA outcomes, characterized by infrequent HBV DNA rebound and no ALT elevations.

In a separate oral presentation, Dr. Nina Le Bert will report findings from a translational study evaluating immunological responses associated with BRII‑179 using samples from the ENSURE and prior BRII-179-835-001 trials. The study identified a novel mechanism whereby BRII‑179 induced CD4+ T‑cell response targeting epitope sequences in the Pre-S1 region that are mismatched to circulating HBV genotypes. These vaccine‑induced T cells remained functionally stable for over two years, persisted during subsequent PEG-IFNα and siRNA treatment. Notably, these T‑cell responses were associated with progressive maturation of HBs‑specific B cells during treatment, an effect linked to enhanced HBsAg loss rates. These findings provide new insights into the potential mechanisms underlying BRII‑179–mediated functional cure.

For more information about Brii Bio's HBV programs visit www.briibio.com.

About Hepatitis B

Hepatitis B virus (HBV) infection is one of the world's most significant infectious disease threats with more than 254 million people infected globally.^[1] Chronic HBV infection is the leading cause of liver disease and an estimated 820,000 people die of complications from chronic HBV infection each year.^[1] HBV is of exceptional concern in China, where 87 million people are chronically infected.^[2]

About BRII-179

BRII-179 is a novel recombinant protein-based HBV immunotherapeutic candidate that expresses the Pre-S1, Pre-S2, and S HBV surface antigens, designed to induce enhanced and broad B-cell and T-cell immunity. In November 2023, the Center for Drug Evaluation (the "CDE") of China's National Medical Products Administration (the "NMPA") granted BRII-179 Breakthrough Therapy Designation.

About Elebsiran

Elebsiran is an investigational subcutaneously administered HBV-targeting siRNA designed to degrade HBV RNA transcripts and limit the production of hepatitis B surface antigen. It has the potential to have direct antiviral activity against HBV and HDV. It is the first siRNA in the clinic to include Enhanced Stabilization Chemistry Plus technology to enhance stability and minimize off-target activity, which potentially can result in an increased therapeutic index. Brii Bio licensed exclusive rights to develop and commercialize elebsiran for the Greater China territory from Vir Biotechnology, Inc. in 2020. In May 2024, the CDE of China's NMPA granted elebsiran Breakthrough Therapy Designation.

About Brii Bio

Brii Biosciences Limited ("Brii Bio", stock code: 2137.HK) is a biotechnology company developing therapies to improve patients' health by addressing high unmet medical needs with limited treatment options. The Company is advancing a broad pipeline of unique therapeutic candidates with lead programs against hepatitis B virus (HBV) infection. The Company is led by a visionary and experienced leadership team and has operations in both China and the United States. For more information, visit www.briibio.com.