DURHAM, N.C., - February 14, 2023 and BEIJING, China – February 15, 2023 – Brii Biosciences Limited (“Brii Bio” or the “Company”, stock code: 2137.HK), a biotechnology company developing therapies to improve patient health and choice across diseases with high unmet need, today announced interim findings from a Phase 2 study, which showed that combination therapy with BRII-835 (also known as VIR-2218) and BRII-179 (also known as VBI-2601) was safe and well-tolerated, induced stronger anti-HBsAg antibody responses and led to improved HBsAg-specific T-cell responses, when compared with BRII-835 or BRII-179 alone. All cohorts achieved HBsAg reduction at the end of treatment with a mean decrease of -1.7 to -1.8 log₁₀ IU/mL. In addition, two participants in combination cohorts achieved maximum reductions in HBsAg at or below the lower limit of quantification (LLOQ) by Week 40, along with robust HBsAg-specific antibody and T-cell responses.

Brii Bio is developing BRII-835, a small interfering ribonucleic acid (siRNA), and BRII-179, a recombinant protein-based HBV immunotherapeutic, as a combination therapy to provide a functional cure for HBV infection. With complementary mechanisms of action previously demonstrated in Phase 1b studies as single agents, this Phase 2 study of BRII-835 and BRII-179 combination shines an important light on how to restore patients’ highly suppressed or exhausted immune responses. Additional data from this trial are expected later this year.

“We’re encouraged by these preliminary data, which reinforce the complementary nature of BRII-835 and BRII-179’s unique modes of action and suggest that, together, they have potential to provide meaningful clinical benefit to chronic HBV patients,” said Man Fung Yuen, M.D., PhD, DSc, Chair and Chief of the Division of Gastroenterology and Hepatology in the University of Hong Kong and principal investigator of the study. “In China alone, there are 87 million people infected with HBV, yet there is no effective functional cure for the disease, and today’s standard of care requires patients to maintain a life-long treatment regimen. A sustained functional cure has the potential to be transformative for HBV patients, mitigating their risk of disease progression and giving patients greater freedom from disease limitations. We look forward to completing this Phase 2 trial with further data analysis.”

“These initial interim results from our Phase 2 study provide important insight to support our clinical approach to identify and explore, alongside our partners, multiple novel combination treatments to improve the probability of achieving a high rate of functional cure in various subpopulations of HBV patients,” said Qing Zhu, Ph.D., Head of China R&D at Brii Bio. “We are eager to continue advancing the development of BRII-835, BRII-179 and BRII-877 (also known as VIR-3434) as part of our lead therapeutic programs in Greater China, as we work to bring the first sustained functional cure to the largest HBV market in the world.”

The Phase 2, randomized, open-label trial is ongoing to evaluate the safety and efficacy of the BRII-835 and BRII-179 as a combination therapy for the treatment of chronic HBV. Results presented are from 50 participants that were broken up into three cohorts to receive nine subcutaneous doses of 100 mg BRII-835 alone (Cohort A) every four weeks through Week 32 or with the addition of 40 μg BRII-179 co-admixed with (Cohort B) or without (Cohort C) 3 MIU IFN-α as co-adjuvant from Week 8 through Week 40, all administered via intramuscular injection.

Data from the Phase 2 study will be shared in an oral presentation, titled Preliminary Safety and Efficacy of the Combination Therapy of BRII-835 and BRII-179 Treating Chronic HBV Infection, at the 32^nd Conference of the Asian Pacific Association for the Study of the Liver (APASL 2023) taking place in Taipei, Taiwan February 18, 2023 at 14:10 local time.

About Hepatitis B

Hepatitis B viral infection (HBV) is one of the world’s most significant infectious disease threats with more than 290 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 each year.¹ HBV is of exceptional concern in China, where 87 million people are infected.²

About BRII-835/BRII-179 Combination

BRII-835/BRII-179 is currently in Phase 2 development in China as a combination therapy for HBV functional cure. BRII-835 is a GalNAc-conjugated siRNA targeting all HBV viral RNAs that has shown to block viral transcription, reduce viral protein, and alleviate immune suppression. BRII-179 is a novel recombinant, protein-based HBV immunotherapeutic that expresses the Pre-S1, Pre-S2, and S HBV surface antigens, and is designed to induce enhanced B-cell and T-cell immunity. Based on licensing agreements with Vir Biotechnology, Inc. and VBI Vaccines, Brii Bio has the exclusive rights to develop and commercialize BRII-835 and BRII-179, respectively, in Greater China.

About Brii Bio

Brii Biosciences is a biotechnology company developing therapies to address some of the world’s most common diseases where patients experience high unmet medical needs, limited choice and significant social stigmas. With a focus on infectious and central nervous system diseases, the Company is advancing a broad pipeline of unique therapeutic candidates with lead programs to develop a novel functional cure for hepatitis B viral infection (HBV) and a first-of-its-kind treatment for postpartum depression (PPD). The Company is led by a visionary and experienced leadership team and has operations in key biotech hubs, including Raleigh-Durham, the San Francisco Bay Area, Beijing and Shanghai. For more information, visit www.briibio.com.

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¹ World Health Organization. (June 2022). Hepatitis B. World Health Organization. Retrieved from https://www.who.int/news-room/fact-sheets/detail/hepatitis-b

² World Health Organization. Hepatitis. World Health Organization. Retrieved from https://www.who.int/china/health-topics/hepatitis#:~:text=There%20are%2087%20million%20people,living%20with%20chronic%20hepatitis%20C.