Brii Biosciences Exercises Option for Vir Biotechnology's VIR-3434, a Broadly Neutralizing Monoclonal Antibody Targeting Hepatitis B in Greater China

Exclusive development and commercialization rights to VIR-3434 in China strengthen Company's leadership and robust clinical pipeline in HBV

Key partnership with Vir enables multitude of combination treatment options as part of Company's strategic approach to developing a functional cure for HBV

DURHAM,N.C. and BEIJING,July 4,2022 -- Brii Biosciences Limited ("Brii Bio" or the "Company",stock code: 2137.HK) a multi-national company developing innovative therapies for diseases with significant unmet medical needs and large public health burdens,today announced that it exercised its option to acquire exclusive development and commercialization rights for VIR-3434 in Greater China as part of its broader collaboration with Vir Biotechnology,Inc. ("Vir",Nasdaq: VIR). This move provides additional growth to the Company's leading clinical pipeline of therapeutic candidates for hepatitis B virus (HBV) and provides an expansive set of potential combination treatment options for Brii Bio to explore as part of its efforts to develop a functional cure for HBV.

VIR-3434,also known as BRII-877,is a broadly neutralizing monoclonalantibody targeting HBV that is currently in Phase 2development. This is Brii Bio's second option exercise to a Vir infectious disease program with two remaining options still available to the Company.

"By exercising our option for VIR-3434 (BRII-877),Brii further solidifies our leading position in developing a functional cure for millions of HBV patients in China," said Li Yan,MD,Ph.D.,Chief Medical Officer of Brii Bio. "Recently announced data by Vir showed that BRII-835 (VIR-2218) and BRII-877 (VIR-3434) are additive to each other resulting in a robust reduction of hepatitis B surface antigen (HBsAg),with no clinically significant safety signals for the combination. We are confident that this new asset further strengthens our HBV pipeline by providing more potent and assured reduction of HBsAg in all patients. BRII-877 (VIR-3434) will be integrated into our innovative drug combination strategies that may lead to a higher functional cure rate across all patient groups. Our continued strategic partnership with Vir and the ongoing expansion of our already robust HBV pipeline reinforces our commitment to patients living with HBV as we aim to explore a range of combination treatment options."

As part of Brii Bio's unique approach to developing a functional cure for HBV by leveraging potential combination treatments,the Company is currently progressing multiple studies with the BRII-179 (VBI-2601) and BRII-835 (VIR-2218) combination,as well as BRII-179 and/or BRII-835 in combination with other agents. Brii Bio's partner,Vir,is also evaluating VIR-2218 (BRII-835) in a Phase 2 study for HBV with selgantolimod (GS-9688),Gilead's investigational TLR-8 agonist,and nivolumab,an approved PD-1 inhibitor. Several combinations involving BRII-835 (VIR-2218),BRII-877 (VIR-3434) and BRII-179 (VBI-2601) are being investigated in Phase 2 studies.

In May 2018,the Company entered into a collaboration,option and license agreement with Vir,under which Brii Bio was granted the option to acquire exclusive rights to certain Vir programs in Greater China. In June 2020,Brii Bio exercised its option to acquire the exclusive rights to further develop and commercialize BRII-835 (VIR-2218) in Greater China.

Under the terms of the agreement,following the exercise of the option for VIR-3434 (BRII-877),Brii Bio will pay an option exercise fee,regulatory and commercial milestone payments,and tiered royalty payments based on net sales with royalty rates from mid-teens to mid-twenties,with such royalty rates or payments subject to certain specified reductions and offsets.

About BRII-877 (VIR-3434)

BRII-877 (VIR-3434) is an investigational subcutaneously administered HBV-neutralizing monoclonal antibody designed to block entry of all 10 genotypes of HBV into hepatocytes and also to reduce the level of virions and subviral particles in the blood. BRII-877 (VIR-3434),which incorporates Xencor's Xtend™ and other Fc technologies,has been engineered to potentially function as a T cell vaccine against HBV in infected patients,as well as to have an extended half-life.

About Brii Bio

Brii Biosciences Limited ("Brii Bio",stock code: 2137.HK) is a biotechnology company based in China and the United States committed to advancing therapies for significant infectious diseases,such as hepatitis B,COVID-19,human immunodeficiency virus (HIV) infection,multi-drug resistant (MDR) or extensive drug resistant (XDR) gram-negative infections,and other illnesses,such as the central nervous system (CNS) diseases,which have significant public health burdens in China and worldwide. For more information,visit www.briibio.com.