Brii Biosciences Announces Positive Data Demonstrating its Long-Acting COVID-19 Neutralizing Antibody Therapy, Amubarvimab/Romlusevimab Combination, Retains Neutralizing Activity Against Live Omicron Virus BA.4/5 and BA.2.12.1 Subvariants

Independent lab results demonstrate that the combination therapy retains neutralizing activity against currently dominant COVID-19 strains,as previously demonstrated with all variants of concern to date

The amubarvimab/romlusevimab combination is commercially available in China and is under review for Emergency Use Authorization by the U.S. Food and Drug Administration (FDA)

DURHAM,N.C. and BEIJING,July 27,2022 --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 new live virus data confirming that the amubarvimab/romlusevimab combination,a long-acting COVID-19 monoclonal antibody (mAb) therapy,retains neutralizing activity against the Omicron BA.4/5 and BA.2.12.1 SARS-CoV-2 subvariants.

Data from the live virus neutralization assay performed at a University of Maryland lab certified by the U.S. National Institutes of Health (NIH) and National Institute of Allergy and Infectious Diseases (NIAID) predict that total serum concentrations of the amubarvimab/romlusevimab combination will remain greater than 170 times the level required for greater than 90% neutralization (Neut99: 0.94 μg/mL) against the live virus,14 days post dose.As a result,adequate therapeutic exposures are expected to persist throughout the treatment period.

The mutations found in the BA.4/5 and BA.2.12.1 subvariants spike protein confer a limited reduction in neutralization activity from wild-type SARS-CoV-2. Based on the human pharmacokinetic data gathered on the amubarvimab/romlusevimab combination,exposures of intravenous amubarvimab 1000mg and romlusevimab 1000mg are expected to remain above the level required for neutralizing activity against BA.4/5 and BA.2.12.1,for the treatment of COVID-19.

"As the COVID-19 pandemic continues to surge with evolving variants,these data further validate the durability and longevity of our long-acting amubarvimab/romlusevimab combination treatment and reinforce its position as a leading investigational monoclonal antibody therapy with potential to retain activity against the most dominating strains that are circulating worldwide," said David Margolis,M.D.,MPH,Vice President and Head of Infectious Diseases Therapy Area at Brii Bio. "We're at a critical moment in the pandemic in which the new Omicron subvariants are more contagious,resulting in a sustained urgency for safe and effective treatment options. We look forward to continuing our discussions with global regulatory bodies as we work to advance this innovative combination therapy for COVID-19 patients in need around the world."

On December 8,2021,the National Medical Products Administration (NMPA) of China approved the amubarvimab/romlusevimab combination for the treatment of adults and pediatric patients (age 12-17 weighing at least 40 kg) with mild and normal type of COVID-19 at high risk for progression to severe disease,including hospitalization or death. The indication of pediatric patients (age 12-17 weighing at least 40 kg) is under a conditional approval. On March 15,2022,the National Health Commission of China added the amubarvimab/romlusevimab combination to its COVID-19 Diagnosis and Treatment Guidelines (9th Pilot Edition) for the treatment of COVID-19. On July 7,the amubarvimab/romlusevimab combination was made commercially available in China.

The U.S. FDA is currently reviewing Brii Bio's Emergency Use Authorization application for the amubarvimab/romlusevimab combination.

About Long-Acting COVID-19 Neutralizing Antibody Therapy,Amubarvimab/Romlusevimab Combination

Amubarvimab and Romlusevimab are non-competing SARS-CoV-2 monoclonal neutralizing antibodies derived from convalesced COVID-19 patients developed in collaboration with the 3rd People's Hospital of Shenzhen and Tsinghua University. 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.

Based on the final results from the U.S. National Institutes of Health (NIH)/National Institute of Allergy and Infectious Diseases (NIAID)-sponsored ACTIV-2 Phase 3 clinical trial with 837 enrolled outpatients,the amubarvimab/romlusevimab combination demonstrates a statistically significant 80% reduction of hospitalization and death with fewer deaths through 28 days in the treatment arm (0) relative to placebo (9),and improved safety outcome over placebo in non-hospitalized COVID-19 patients at high risk of clinical progression to severe disease. Similar efficacy rates were observed in participants initiating therapy early (0-5 days) and late (6-10 days),following symptom onset,providing critically needed clinical evidence in COVID-19 patients who were late for treatment.

The live virus testing data,as well as pseudovirus testing data from multiple independent labs,have demonstrated that the amubarvimab/romlusevimab combination 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),AY.4.2 (Delta Plus),C.37 (Lambda),B.1.621 (Mu),B.1.1.529-BA.1 (Omicron),and BA.1.1,BA.2,BA.2.12.1,BA.4/5 (Omicron subvariants).

About Brii Bio

Brii Biosciences Limited ("Brii Bio",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,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.