Brii Biosciences Announces Topline End-of-Treatment Data from Phase 2b ENRICH and ENHANCE Studies in Chronic Hepatitis B

Zhitong Finance APP News: Brii Biosciences-B (02137) announced the end-of-treatment (EOT) results from its ongoing Phase 2b ENRICH and ENHANCE studies. These studies aim to evaluate sequential and concurrent combination regimens of BRII-179 with elebsiran and pegylated interferon alpha (PEG-IFNα) in chronic hepatitis B virus (HBV) infection.

ENRICH and ENHANCE are two Phase 2b studies designed to further elucidate the role of BRII-179 in the treatment of chronic hepatitis B virus (HBV) infection and to identify the optimal combination regimen for subsequent development. The ENRICH study evaluates the efficacy of BRII-179 as an immune activator administered prior to treatment with elebsiran and pegylated interferon-alpha (PEG-IFNα). The ENHANCE study assesses a triple-combination synchronous dosing regimen of BRII-179, elebsiran, and PEG-IFNα, with the aim of improving functional cure rates.

At the end of treatment, the ENRICH study demonstrated that in a regimen involving initial treatment with BRII-179 followed by combination therapy with elebsiran and PEG-IFNα, hepatitis B surface antigen (HBsAg) clearance rates of 42.9% (42/98) and 40.0% (20/50) were achieved under two different BRII-179 dosing regimens (corresponding to five doses administered once every three weeks and seven doses administered once every two weeks, respectively). These results are consistent with the HBsAg clearance rate of 41.9% (13/31) observed in patients previously treated with BRII-179 in Cohort 4 of the ENSURE study, supporting the immune-priming effect of BRII-179. The Company has communicated with the Center for Drug Evaluation of the National Medical Products Administration regarding potential registration-enabling studies and has reached preliminary consensus.

At the end of treatment, no increase in HBsAg clearance rate was observed with the triple simultaneous administration regimen evaluated in the ENHANCE (Part A-1) study compared to Cohorts 2 and 3 of the ENSURE study (HBsAg clearance rates at the end of treatment in ENSURE Cohorts 2 and 3: 29.7% (11/37); this study: 25.5% (25/98)). However, a higher HBsAg clearance rate was observed with this triple regimen compared to the PEG-IFNα control group (10.2% (5/49)).

Subgroup analysis of the ENRICH study suggests that this treatment regimen may exhibit differential efficacy in patients with higher baseline HBsAg levels (1,000–3,000 IU/mL), consistent with previous observations from ENSURE Cohort 4. This indicates that BRII-179 may induce a favorable immune response in this population with greater treatment difficulty, regardless of baseline HBsAg levels.

The A-2 part of the ENHANCE study also evaluated a sequential treatment regimen aimed at potentially shortening the course of PEG-IFNα therapy, consisting of BRII-179 combined with elebsiran for the first 24 weeks, followed by elebsiran combined with PEG-IFNα for the subsequent 24 weeks. At the end of treatment, this regimen achieved an HBsAg clearance rate of 22.5% (18/80), suggesting that a full course of PEG-IFNα therapy remains critical for achieving optimal cure outcomes.

HBsAg clearance is a key endpoint for assessing functional cure regimens; however, post-treatment follow-up is still required to confirm the risk of rebound and the durability of efficacy. No new safety signals were identified in either study. The Company plans to present detailed data, including additional efficacy and safety results, subgroup analyses, and follow-up findings, at academic conferences in the second half of 2026.

Dr. David Margolis, Chief Medical Officer of the Company, stated, “The end-of-treatment data mentioned above provide important evidence for evaluating the relative performance of the ENRICH and ENHANCE study designs. Although longer-term follow-up is still needed to assess the durability of HBsAg clearance, the currently observed data are highly consistent with the end-of-treatment and post-treatment results from multiple previous studies, supporting the ENRICH design as the preferred option for registration-enabling studies. We look forward to sharing more complete data later this year.”

As previously disclosed, given the ongoing arbitration (the “Arbitration”) with Vir Biotechnology, Inc., and the uncertainty surrounding the outcome of the Arbitration or any potential settlement of the related claims, including their content and timing, the Company believes that the future of the elebsiran program is uncertain. In particular, unless and until the claims in the Arbitration are resolved satisfactorily, the Company will be unable to invest in conducting Phase 3 clinical studies of any hepatitis B combination therapy regimens containing elebsiran. The Company will continue to assess relevant developments and their impact on the prospects for continuing the elebsiran program, and will provide updates to its shareholders and the public in a timely manner in accordance with applicable regulations.