Brii Bio Presents Late-Breaking Data from Its Phase 2 ENRICH and ENHANCE Studies at AASLD 2026, Supporting BRII-179-Based Priming and Enrichment Strategy for HBV Functional Cure

• Data across five Phase 2 studies of BRII-179, including ENSURE, ENRICH and ENHANCE, support its potential role in priming HBV-specific immune responses and improving functional cure rates with siRNA-based therapies
• ENRICH prospectively reproduced the BRII-179 priming effect previously observed in ENSURE Cohort 4, with 41.9% of participants achieving HBsAg loss at end of treatment (EOT) and 32.4% maintaining HBsAg loss through 24 weeks post-EOT
• Findings across ENSURE, ENRICH and ENHANCE support the potential of BRII-179-based strategies to improve HBsAg loss rates among participants with higher baseline HBsAg levels, a population that remains particularly difficult to cure

DURHAM, N.C. and BEIJING, Nov. 6, 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-treatment (EOT) and follow-up results from its Phase 2b ENRICH and ENHANCE studies in three late-breaking presentations at the American Association for the Study of Liver Diseases (AASLD) The Liver Meeting®, taking place in Denver, Colorado, from November 5 to 9, 2026.

The new results add to data generated across five Phase 2 studies of BRII-179. In particular, ENSURE, ENRICH and ENHANCE have progressively evaluated the potential of BRII-179 to prime HBV-specific immunity, enrich immunologically responsive participants and inform the design of combination regimens aimed at achieving durable hepatitis B surface antigen (HBsAg) loss and functional cure.

Cohort 4 of the ENSURE study first identified the potential priming and enrichment role of BRII-179, with higher functional cure rates observed among BRII-179-experienced participants, particularly those who developed anti-HBs responses. The ENRICH study subsequently evaluated this strategy prospectively by administering BRII-179 every 3 or 2 weeks for 12 weeks before elebsiran and pegylated interferon alpha (PEG-IFNα).

Across the two BRII-179 dose regimens in the ENRICH study, 41.9% of participants achieved HBsAg loss at EOT and 32.4% maintained HBsAg loss at 24 weeks post EOT; both rates were consistent with the observations from ENSURE Cohort 4.

The ENHANCE study further evaluated how BRII-179 may be incorporated into a triple combination regimen of BRII-179, elebsiran and PEG-IFNα. In Part A1, concurrent triple therapy with BRII-179, elebsiran and PEG-IFNα achieved higher HBsAg loss rates than PEG-IFNα monotherapy at EOT, 25.5% versus 10.2%, and at 24 weeks post-EOT, 17.3% versus 6.1%. Part A2 of the ENHANCE study evaluated a 24-week priming phase with BRII-179 and elebsiran, followed by elebsiran and a shortened, 24-week course of PEG-IFNα. At EOT, 22.5% of participants achieved HBsAg loss. Anti-HBs responders following BRII-179 and elebsiran priming, defined as participants with anti-HBs ≥ 10 IU/L at Week 24, demonstrated higher HBsAg loss rates at EOT than nonresponders (30.6% vs 15.9%). At eight weeks post-EOT, the HBsAg loss rates further increased to 25.0% in the overall population and 33.3% among anti-HBs responders. These findings provide additional insights into the priming effect of BRII-179 in improving responses to subsequent combination therapy with siRNA and PEG-IFNα.

Across the ENRICH and ENHANCE studies, encouraging HBsAg loss rates were observed among participants with higher baseline HBsAg levels. In the ENRICH study, 32.1% of participants with baseline HBsAg levels greater than 1,000 IU/mL and up to 3,000 IU/mL achieved HBsAg loss at EOT and 20.8% at 24 weeks post-EOT. In Part A1 of the ENHANCE study, among participants with baseline HBsAg levels greater than 1,000 IU/mL, HBsAg loss was observed in 24.2% of those receiving triple therapy at EOT and 18.2% at 24 weeks post-EOT, compared with 0% in the PEG-IFNα monotherapy group at both time points. In ENHANCE Part A2, a meaningful HBsAg loss rate was also observed in this high baseline subgroup at EOT (14.6%) and eight weeks post-EOT (16.7%). These results support further evaluation of BRII-179-based priming strategies in participants with higher baseline HBsAg levels, a population in which functional cure remains particularly challenging based on historical data.

Across the studies, the regimens were generally safe and well tolerated.

"The findings across our Phase 2b studies provide a stronger scientific foundation for the continued evaluation of BRII-179-based priming and enrichment strategies," said Dr. David Margolis, Chief Medical Officer of Brii Bio. "They also offer important insights into how BRII-179 may be used to prime HBV-specific immunity and how early immune responses could help inform subsequent treatment. Together, these learnings may help guide the design of future studies, including in people with higher baseline HBsAg levels for whom achieving functional cure remains particularly difficult."

Oral presentation details are as follows:

Publication Number: 5009

Title: Efficacy and safety of sequential BRII-179, elebsiran, and pegylated interferon alfa therapy in chronic hepatitis B virus infection: end-of-treatment and follow-up results from the phase 2 ENRICH study

Presenter: Jinlin Hou, M.D., Director of Institute of Hepatology of Guangdong, Director of Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Department of Infectious Diseases & Hepatology Unit, Nanfang Hospital, Southern Medical University

• Across Cohorts A and B, 41.9% (62/148) of participants achieved HBsAg loss at the end of treatment and 32.4% (48/148) maintained HBsAg loss through 24 weeks after treatment.
• Among participants with baseline HBsAg levels greater than 1,000 IU/mL and up to 3,000 IU/mL, 20.8% (11/53) achieved HBsAg loss at 24 weeks post-EOT, demonstrating the potential priming effect of BRII-179 in improving the HBsAg loss rate in patients with high baseline HBsAg levels.
• The regimen was generally safe and tolerated, with most commonly reported adverse events consistent with the known side effects of PEG-IFNα.

Publication Number: 5017

Title: Elebsiran plus BRII-179 and peginterferon alfa achieve greater HBsAg loss and enhanced immune responses compared with peginterferon alfa alone in virologically suppressed chronic hepatitis B: Results from the Phase 2 ENHANCE Part A1

Presenter: David Margolis, M.D., M.P.H., Chief Medical Officer of Brii Biosciences

• In virologically suppressed adults with chronic HBV infection, BRII-179, elebsiran and PEG-IFNα triple therapy group achieved higher HBsAg loss rates than PEG-IFNα monotherapy group at EOT (25.5% [25/98] vs 10.2% [5/49], p=0.0301) and 24 weeks post-EOT (17.3% [17/98] vs 6.1% [3/49]).
• Among participants with baseline HBsAg >1,000 IU/mL, HBsAg loss was observed in 24.2% (8/33) at EOT and 18.2% (6/33) at 24 weeks post-EOT in the triple therapy group, versus 0% (0/18) in the PEG-IFNα monotherapy group at both time points.
• Triple therapy elicited greater anti-HBs responses. At EOT, 50.0% (49/98) and 40.8% (40/98) of participants in the triple therapy group achieved anti-HBs levels ≥10 IU/L and ≥100 IU/L, respectively, whereas anti-HBs responses remained limited in the PEG-IFNα monotherapy group. Exploratory findings suggest a potential association between higher anti-HBs levels at EOT and subsequent maintenance of HBsAg loss.
• The regimen was generally safe and well tolerated, with commonly reported adverse events generally consistent with the known profile of PEG-IFNα. No new or unexpected safety signals were identified.

Poster presentation details are as follows:

Publication Number: 5029

Title: Immune Priming With BRII-179 and Elebsiran Enables Shortened Pegylated Interferon Alfa Treatment While Maintaining HBsAg Loss in Participants With Chronic HBV Infection: Results From ENHANCE Part A2

• BRII-179 + elebsiran priming enabled a 50% reduction in PEG-IFNα treatment duration, while maintaining an HBsAg loss rate (22.5% [18/80] at EOT, 25.0% [20/80] at 8 weeks post-EOT) comparable to that observed in Part A1 (25.5%),where participants received 48 weeks of concurrent triple combination.
• EOT HBsAg loss rates were higher in participants with baseline HBsAg ≤ 1,000 IU/mL (34.4% [11/32], while a meaningful proportion of participants with baseline HBsAg >1,000 IU/mL also achieved HBsAg loss (14.6% [7/48].
• At Week 24 (end of the priming phase), anti-HBs levels reached ≥ 10 IU/L and ≥ 100 IU/L in 45.0% (36/80) and 21.3% (17/80) of participants, respectively. Anti-HBs responder, defined as anti-HBs ≥ 10 IU/L at Week 24, demonstrated higher HBsAg loss rates at EOT than nonresponders (30.6% [11/36] vs 15.9% [7/44]).
• At Week 56 (8 weeks post-EOT), the HBsAg loss rate further increased to 37.5% (12/32) in participants with baseline HBsAg ≤ 1,000 IU/mL, to 16.7% (8/48) in participants with baseline HBsAg ＞1,000 IU/mL, and to 33.3% (12/36) among anti-HBs responders.
• The regimen was generally safe and well tolerated. During the BRII-179 + elebsiran priming period, Grade ≥ 3 AEs were rare. Following addition of PEG-IFNα, the safety profile is consistent with the known profile of PEG-IFNα, with certain adverse events reported less frequently in Part A2 than in Part A1, in the context of the shorter duration of PEG-IFNα treatment in Part A2.

For more information about Brii Bio’s HBV candidates, 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, and is designed to induce enhanced and broad B-cell and T-cell immunity. In November 2023, the Center for Drug Evaluation (the "CDE") of the 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 hepatitis B virus 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 obtained exclusive license from Vir Biotechnology, Inc. in 2020 for the research, development, and commercialization of elebsiran in Greater China including Mainland China, Macau, Hong Kong and Taiwan. 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 patient health by addressing diseases and high unmet medical needs with limited treatment options. The Company is advancing a broad pipeline of differentiated therapeutic candidates, including internally discovered programs enabled by its in-house RNA technology capabilities such as its proprietary BRiSC^TM siRNA discovery platform. The Company is led by an experienced leadership team and has operations in China and the United States. For more information, visit www.briibio.com.