Brii Biosciences Announces Positive Data from the Phase 3 ACTIV-2 Trial Evaluating Combination BRII-196 and BRII-198 in Non-Hospitalized COVID-19 Patients

DURHAM,N.C. and BEIJING,Aug. 25,2021 -- 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 need and large public health burden,today announced that its SARS-CoV-2 (virus that causes COVID-19) neutralizing monoclonal antibody combination therapy,BRII-196/BRII-198 ("combination BRII-196/BRII-198"),demonstrated a statistically significant reduction of 78%,relative risk ([95% CI]: 0.22 [0.05,0.86],p<0.00001 (nominal,one-sided)) in the combined endpoint of hospitalization and death compared with placebo in 837 non-hospitalized COVID-19 patients at high risk of clinical progression. In this interim analysis of the ACTIV-2 trial based on partial follow-up of the 837 participants,a reduction in both hospitalizations (12 active vs. 45 placebo) and deaths (1 active vs. 9 placebo) was observed. Additional subgroup analysis may further delineate the clinical benefits of early (≤5 days) versus late (6-10 days) treatment with BRII-196/BRII-198 following symptom onset,providing unique insight to inform real-world treatment decisions.

The BRII-196/BRII-198 arm of the Phase 2/3 ACTIV-2 platform trial,which is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID),part of the National Institutes of Health (NIH),evaluated 837 outpatients,enrolled within 10 days of symptom onset and at high risk of clinical progression (i.e. age ≥ 60 or the presence of other medical conditions at any age). Following a clear demonstration of statistical significance,which evaluated approximately 69% of participants through the primary endpoint as part of a pre-specified review,the independent data safety monitoring board (DSMB) permitted the early release of these results while the complete study follow-up remains ongoing. The participants enrolled are evaluated for the combined primary endpoint of hospitalizations and death relative to placebo in the 28 days following treatment.

Grade 3 or higher adverse events (AEs) were observed less frequently among the BRII-196/BRII-198 arm (3.8% active vs. 13.4% placebo),with few events being considered drug related. There were no drug related serious adverse events (SAEs) or deaths observed in either arm. There were no severe infusion reactions observed.

"We are thrilled to announce the interim Phase 3 results from ACTIV-2,which demonstrate a significant reduction in the endpoint of hospitalizations or death among non-hospitalized people with mild COVID-19 who were treated with BRII-196/BRII-198," said Teresa H. Evering,M.D.,M.S.,Weill Cornell Medicine,co-lead investigator of BRII-196/BRII-198 in ACTIV-2. "The devastating resurgence in COVID-19 cases over the past several months is a sobering reminder of how desperately we need treatment options."

"ACTIV-2 has shown the benefits of BRII-196/BRII-198 as a treatment for people who were at high risk for progression to severe disease and we expect that the final study results will solidify this combination monoclonal antibody treatment as a new COVID-19 therapeutic option," saidEric S. Daar,Lundquist Institute at Harbor-UCLA Medical Center,co-lead investigator of BRII-196/BRII-198 in ACTIV-2.

"We are very pleased with the positive results of this important global trial," said Zhi Hong,Ph.D.,CEO of Brii Biosciences. "As we all continue to research and evolve our understanding of this novel virus,Brii Biosciences is committed to advancing global standards of treatment for a broad range of patients at various stages of disease as well as those affected by the newly-emerging COVID-19 variants. We look forward to completing the analysis of this full data set and sharing our findings from this large global trial."

Upon completion of this study,the full analysis of the ACTIV-2 dataset will include participants enrolled in the United States,Brazil,South Africa,Mexico,Argentina and the Philippines between January and July of 2021 – a period of rapid global emergence of novel SARS-CoV-2 variants. Data on the clinical efficacy of combination BRII-196/BRII-198 by variant type will also be evaluated as part of the study. Current in vitro pseudovirus testing data suggests that combination BRII-196/BRII-198 retains activity against major SARS-CoV-2 variants of concern,including the following commonly identified variants,B.1.1.7 (Alpha),B.1.351 (Beta),P.1 (Gamma),B.1.429 (Epsilon),B.1.617.2 (Delta),and C.37 (Lambda).

Combination BRII-196/BRII-198 was generally safe and well tolerated in Phase 1 and Phase 2 clinical trials conducted to date. In early 2020,Brii Biosciences partnered with Tsinghua University and Shenzhen Third People's Hospital to establish TSB Therapeutics for the development of BRII-196 and BRII-198. The Phase 2 clinical trial in China (NCT04787211) is ongoing led by Dr. Nanshan Zhong,the Academician of the Chinese Academy of Engineering and Director of the National Clinical Medical Research Center for Respiratory Diseases at the First Affiliated Hospital of Guangzhou Medical University. In response to the recent emergence of COVID-19 cases in China,including cases caused by the Delta variant,Brii Biosciences has cooperated with governmental agencies and hospitals in China to supply BRII-196/BRII-198 for emergency use in Guangzhou,Shenzhen,Ruili,Kunming,Nanjing,Yangzhou,Zhangjia Jie and Zhengzhou.

About ACTIV-2

The ACTIV-2 trial (NCT04518410) is sponsored by NIAID,one of the institutes of the NIH,and is led by the NIAID-funded AIDS Clinical Trials Group (ACTG). ACTIV-2 is part of NIH's Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV),a public-private partnership program to create a coordinated research strategy that prioritizes and speeds development of the most promising treatments and vaccines.

The ACTIV-2 master protocol evaluates the safety and efficacy of investigational agents for the treatment of symptomatic non-hospitalized adults with COVID-19 under a randomized,blinded,controlled adaptive platform. Participants identified as being at high risk for progression to more severe disease were eligible for enrollment onto combination BRII 196/BRII-198 or placebo. Phase 3 of the study was designed to determine if combination BRII-196/BRII-198 prevents the composite endpoint of either hospitalization or death through study day 28. The Phase 3 trial was a continuation of the Phase 2 trial in which combination BRII-196/BRII-198 met study-defined safety and efficacy criteria.

About BRII-196 and BRII-198

BRII-196 and BRII-198 are non-competing SARS-CoV-2 monoclonal neutralizing antibodies derived from convalesced COVID-19 patients. They have been specifically engineered to reduce the risk of antibody-dependent enhancement and prolong the plasma half-lives for potentially more durable treatment effect. Their non-overlapping epitope binding regions provide a high degree of neutralization activity against SARS-CoV-2.

Investigational New Drug (IND) applications have been submitted for the combination therapy to the U.S. Food and Drug Administration (FDA),the China National Medical Products Administration (NMPA) and the Department of Health in Hong Kong,China. Combination BRII-196/BRII-198 was generally safe and well tolerated in Phase 1 studies,supporting evaluation in later stage studies. In addition to the collaboration with NIAID,Brii Biosciences is conducting additional studies in China,evaluating the pharmacokinetics and safety of combination BRII-196/BRII-198 as well as a Phase 2 efficacy study of combination BRII-196/BRII-198 for the treatment of COVID-19.

About Brii Biosciences

Brii Biosciences Limited ("Brii Biosciences",or the "Company",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 virus (HBV),human immunodeficiency virus (HIV),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.

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