A 42.9% HBsAg loss rate at end of treatment is the number Brii Biosciences is betting its HBV franchise on, and it carries real weight when you consider that PEG-IFNα monotherapy produces end-of-treatment HBsAg clearance of roughly 4.4% in meta-analysis data. That gap between standard-of-care and Brii’s ENRICH regimen, which primes patients with BRII-179 before adding elebsiran and PEG-IFNα, is the central argument for a functional cure strategy that the company has now tested across three Phase 2b studies: ENSURE, ENRICH, and ENHANCE.
The ENRICH result, 42.9% HBsAg loss across 98 patients on the five-dose BRII-179 schedule, mirrors the 41.9% seen in ENSURE Cohort 4 patients who had prior BRII-179 exposure. That cross-study consistency is meaningful; it suggests the immune-priming effect of BRII-179 is reproducible, not a one-trial artifact. More commercially relevant, subgroup data from ENRICH hint at differentiation in patients with baseline HBsAg between 1,000 and 3,000 IU/mL, a segment historically resistant to interferon-based therapy. ENHANCE told a more complicated story: the concurrent triple combination in Part A-1 produced only 25.5% HBsAg loss, falling short of ENSURE’s combination cohorts at 29.7%, though still well above the PEG-IFNα control arm at 10.2%. That underperformance in the concurrent design narrows the question Brii now has to answer before committing to a registrational regimen: sequential priming appears superior, but detailed ENRICH and ENHANCE data presentations in the second half of 2026 will need to show durability at follow-up, not just end-of-treatment snapshots.
Separately, the first patient was dosed in a clinical study of BRII-5395, an internally discovered mRNA therapeutic vaccine for advanced hepatocellular carcinoma. The company describes this as the first clinical evaluation of an RNA-based therapeutic originating from its internal discovery engine, a signal that Brii is deliberately building pipeline depth beyond its licensed HBV assets. The company holds approximately $260 million in cash as of June 30, 2026, which gives it runway to run both tracks without forcing an immediate partnership decision.
The competitive clock is running. Bepirovirsen, the GSK/Ionis antisense oligonucleotide, achieved functional cure in roughly 20% of chronic HBV patients in Phase 3 trials and is now in regulatory review. Brii’s priming regimen outperforms that benchmark on raw HBsAg loss, but the durability data expected later this year will determine whether that advantage holds at sustained off-treatment follow-up, which is the number regulators and prescribers will actually require before any functional cure label becomes real.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
