Therapeutic vaccine BRII-179 restores HBV-specific immune responses in patients with chronic HBV in a phase Ib/IIa study

Background & aims: Functional cure of chronic HBV infection (CHB) without life-long treatment requires the restoration of defective HBV-specific humoral and cellular immunity. Therapeutic vaccines based on the major structural and non-structural proteins have been tested in patients with CHB but have shown scarce immunogenicity. BRII-179, also known as VBI-2601, is a novel formulation comprised of all 3 HBV surface envelope proteins (Pre-S1, Pre-S2, and S). Safety, antiviral activity, and immunogenicity of BRII-179 admixed with co-adjuvant interferon (IFN)-α were assessed in patients with CHB.

Method: This randomized, open-label, controlled phase Ib/IIa study included 2 dose levels, 20 μg BRII-179 (Part 1, n = 25) and 40 μg BRII-179 (Part 2, n = 24). Patients, virally suppressed under nucleos(t)ide analogue (NA) therapy were randomized 1:2:2 into 3 cohorts in Part 1 and 1:1 into 2 cohorts in Part 2 to receive 4 monthly intramuscular injections of BRII-179 admixed with/without 3 MIU IFN-α. Antibody and cellular responses to HBsAg, as well as evolution of circulating HBsAg were monitored.

Results: Both 20 μg and 40 μg BRII-179 with/without IFN-α were well tolerated with no severe adverse events. BRII-179 induced anti-HBs responses in >30% patients in all treatment cohorts, however, moderate anti-Pre-S1 or anti-Pre-S2 antibody responses were only observed in patients receiving BRII-179 with IFN-α. BRII-179 also restored S-, Pre-S1-, Pre-S2-specific IFN-γ-producing T-cells in the majority of treated patients. Overall, no notable reduction of HBsAg was observed after BRII-179 treatment.

Conclusion: In patients with CHB under NA therapy, BRII-179 with/without IFN-α exhibited a good safety profile and induced HBV-specific B- and T-cell immune responses. These data support further clinical evaluation of BRII-179 in combination with other therapies.

Clinical trial number: ACTRN12619001210167.

Lay summary: BRII-179 is a therapeutic vaccine designed to improve the immune response in patients with chronic hepatitis B. In this study, BRII-179 alone or with a low dose of interferon-α was safe, well tolerated, and induced enhanced HBV-specific antibody and T-cell responses in patients with chronic hepatitis B. However, BRII-179 treatment alone had minimal effect on patient's virological status. The potential of BRII-179 to achieve a functional cure in conjunction with other agents is being evaluated in the clinic.