Chinese biotechnology company Brii Biosciences Limited (Brii Bio) (HK:2137) has announced end-of-treatment (EOT) results from its ongoing Phase 2b ENRICH and ENHANCE studies investigating sequential versus concurrent combination regimens of BRII-179 with elebsiran and PEG-IFN alpha for chronic hepatitis B virus (HBV) infection.

The two Phase 2b studies are designed to further define the role of BRII-179 in chronic HBV treatment and to select the optimal combination regimen for future development. The ENRICH study evaluates BRII-179 as a priming therapy administered prior to elebsiran and PEG-IFN alpha treatment. ENHANCE evaluates a concurrent triple combination regimen of BRII-179, elebsiran, and PEG-IFN alpha to enhance the functional cure rates.

According to Brii Biosciences, at EOT the ENRICH study demonstrated hepatitis B surface antigen (HBsAg) loss rates of 42.9% (42/98) and 40.0% (20/50) across two different BRII-179 dosing schedules, being 5 doses administered once every 3 weeks versus 7 doses administered once every 2 weeks, respectively. These results were consistent with the HBsAg loss rate observed in ENSURE Cohort 4, 41.9% (13/31) in patients with prior BRII-179 treatment, supporting the immune priming role of BRII-179. The company had engaged with the Center for Drug Evaluation of the China's National Medical Products Administration and reached preliminary alignment regarding a potential registrational study.

At EOT the ENHANCE (Part A-1) study evaluating a concurrent triple combination did not demonstrate improved HBsAg loss rates compared with ENSURE Cohorts 2 and 3, 29.7% (11/37), with an observed rate of 25.5% (25/98). However, higher HBsAg loss rates were observed compared with the PEG-IFN alpha control arm, 10.2% (5/49).

Brii Bio said that subgroup analyses from the ENRICH study suggest potential differentiation in subjects with higher baseline HBsAg levels (1000-3000 IU/mL), consistent with prior findings from ENSURE Cohort 4, indicating that BRII-179 may induce beneficial immune responses regardless of baseline HBsAg levels in this difficult-to-treat population.