Brii Bio Presents Cross-Study Analysis of Post-Treatment HBsAg Rebound at APASL 2026

- Participants achieving HBsAg loss with pegylated interferon alfa (PEG-IFNα) ± elebsiran or BRII-179 demonstrated favorable off-treatment clinical outcomes, with most HBsAg rebounds <10 IU/mL and HBV DNA rebound infrequent and not associated with clinically significant ALT elevation. These findings indicate durable post‑treatment immunological control, supporting the potential for safe nucleos(t)ide reverse transcriptase inhibitor (NRTI) discontinuation in regimens combining PEG-IFNα with novel therapeutic modalities.

- Shorter NRTI consolidation was not associated with higher HBsAg rebound rates, suggesting that shortening or potentially eliminating the NRTI consolidation period may be feasible in these combination regimens.

DURHAM, N.C. and BEIJING, April 26, 2026 /PRNewswire/ -- Brii Biosciences Limited  ("Brii Bio," "Brii," 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, presented a cross-study analysis of post-treatment hepatitis B surface antigen (HBsAg) rebound profiles at the 35^th Annual Meeting of Asian Pacific Association for the Study of the Liver (APASL 2026), taking place from April 22-25, 2026 in Istanbul, Turkey.

This analysis evaluated post-end-of-treatment (EOT) HBsAg rebound in NRTI-experienced participants with chronic hepatitis B virus (HBV) infection who achieved HBsAg loss in the Phase 2 ENSURE study or the Phase 2 BRII-179-002 study. The Phase 2 ENSURE study is designed to assess the safety and efficacy of combination approaches aimed at improving functional cure outcomes. Cohorts 1-3 evaluate elebsiran in combination with PEG-IFNα compared to PEG-IFNα monotherapy, while Cohort 4 evaluates the potential role of BRII-179 in identifying immunologically responsive patients and improving HBsAg loss rate. BRII-179-002 is a multicenter, randomized, double-blind, proof-of-concept Phase 2 study that evaluates BRII-179 as an add-on therapy to PEG-IFNα.

Data from the two studies were pooled to assess the incidence, magnitude and clinical relevance of HBsAg rebound following EOT in participants treated with PEG‑IFNα alone or in combination with elebsiran or BRII‑179. Across studies, participants demonstrated favorable off‑treatment clinical outcomes. All HBsAg rebounds remained below 100 IU/mL with most rebounds remaining below 10 IU/mL. HBV DNA rebound was infrequent and not associated with clinically meaningful alanine aminotransferase (ALT) elevations following NRTI discontinuation. Together, these results suggest durable post‑treatment immunological control and further support the potential for safe discontinuation of NRTIs in PEG‑IFNα-based combination with novel therapeutic modalities. Notably, shorter NRTI consolidation periods (12 to 20 weeks versus 24 weeks) were not associated with higher HBsAg rebound rates, suggesting that shortening—and potentially eliminating—the NRTI consolidation period may be feasible in future treatment strategies.

"We are encouraged by the growing evidence showing that our novel therapeutic combinations can achieve not only rapid HBsAg loss, but also durable immunological control after treatment withdrawal," said David Margolis, M.D., Chief Medical Officer of Brii Bio. "These findings strengthen our confidence in the potential of BRII‑179 and elebsiran as components of next‑generation HBV cure strategies, and we look forward to additional readouts from our ongoing studies throughout 2026."

Additional details of the oral presentation are as follows:

Title: Cross-study Analysis of HBsAg Rebound Following Treatments of Elebsiran/BRII-179 in Combination with Peginterferon Alfa

Session/Presentation Type: Oral Presentation Session 58

Date and time: 13:40 - 15:10 on April 25 (UTC+3)

Presenter: Jidong Jia, M.D., Ph.D., Professor of Medicine at the Liver Research Centre, Beijing Friendship Hospital, Capital Medical University in Beijing, China

• Post‑EOT HBsAg rebound was observed in 24 of 55 participants (43.6%) with similar rates during NRTI consolidation (13/55, 23.6%) and after NRTI discontinuation (11/41, 26.8%).
• Shorter NRTI consolidation was not associated with higher HBsAg rebound rates after NRTI withdrawal, with 15.0% (3/20) of participants receiving 12–20 weeks of NRTI consolidation and 23.8% (5/21) of those receiving 24 weeks experiencing HBsAg rebound by 24 weeks after NRTI discontinuation.
• The magnitude of HBsAg rebound was limited, with all rebounds <100 IU/mL and 75.0% (18/24) remaining <10 IU/mL. HBV DNA rebound after NRTI discontinuation was infrequent, with >90% (38/41) of participants maintaining HBV DNA <LLOQ at the last available visit. No ALT flares were observed; one participant exceeded the normal range and received NRTI retreatment at investigator discretion.

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.

SOURCE Brii Biosciences Limited