Brii Bio Announces Positive Data Demonstrating its Long-Acting COVID-19 Neutralizing Antibody Therapy, Amubarvimab/Romlusevimab Combination, Retains Neutralizing Activity Against Omicron BA.2 Subvariant

Studies conducted by independent labs demonstrate the amubarvimab/romlusevimab combination retains neutralizing activity against COVID-19 Omicron variant

Review of the monoclonal antibody combination therapy is underway by the U.S. Food and Drug Administration (FDA) for Emergency Use Authorization

DURHAM,N.C. and BEIJING,May 9,2022 --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 data demonstrating that its long-acting COVID-19 neutralizing antibody therapy,the amubarvimab/romlusevimab combination,retains neutralizing activity against the Omicron BA.2 SARS-CoV-2 subvariant.

These data,which were assessed in both in vitro pseudovirus neutralization testing and through live virus neutralization assays conducted at independent labs,suggest that exposures of intravenous amubarvimab 1000mg and romlusevimab 1000mg are expected to remain above the level required for neutralizing activity against BA.2,for the treatment of COVID-19 based on the human pharmacokinetic data gathered on the amubarvimab/romlusevimab combination.

Data from the live virus neutralization assay performed at a lab certified by the U.S. National Institutes of Health (NIH) and National Institute of Allergy and Infectious Diseases (NIAID) at the University of Maryland suggest that total serum concentrations of the amubarvimab/romlusevimab combination will remain 60 times the level required for greater than 90% neutralization (Neut99: 2.50 μg/mL) against the live virus isolate BA.2,14 days post dose.As a result,even though the mutations found in the BA.2 subvariant spike protein increase the IC50 relative to wild-type SARS-CoV-2,adequate therapeutic exposures are expected to persist for a minimum of 2 weeks and longer.

"Omicron BA.2 subvariant cases now represent the majority of COVID-19 infections globally,so these data offer timely insights into the longevity and durability of the amubarvimab/romlusevimab combination as a potential new tool to help patients in need of more treatment options," said David Margolis,M.D.,MPH,Vice President and Head of Infectious Diseases Therapy Area at Brii Bio. "There continues to be a critical need for highly effective therapies against COVID-19 infection,which can greatly reduce the risk of hospitalization and death in individuals at high risk. Our combination therapy is one of the few treatments that is proven to retain neutralizing activity against Omicron BA.2 and all previous variants of concern as a result of its unique combination strategy."

Current in vitro pseudovirus testing data suggests 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 and BA.2 (Omicron subvariants).

"Brii stepped up to this public health challenge. We made a point to work with some of the most respected public sector partners,including the 3rd People's Hospital of Shenzhen,Tsinghua University,the U.S. NIH,NIAID,and AIDS Clinical Trial Group. We worked expeditiously with our partners to deliver best-in-class research and data that demonstrate improved clinical outcomes with amubarvimab/romlusevimab combination for a broad range of COVID-19 patients at high risk of severe disease progression," said Rogers Luo,President and General Manager of Greater China of Brii Bio. "As a relatively young biotech company,we have worked tirelessly to advance amubarvimab/romlusevimab combination as a treatment option to help address this global crisis. We have received purchase orders and stockpiling requests from nearly 20 provincial Health Commissions as well as more than 100 healthcare institutions and commercial organizations.We will continue to work closely with global regulatory bodies and our contract development and manufacturing organization (CDMO) to deliver this clinically proven therapy to patients in need."

Brii Bio's Emergency Use Authorization application for the amubarvimab/romlusevimab combination is under review by the U.S. FDA and is pending on satisfactory completion of FDA inspection of the manufacturing sites at our CDMO. Following China's initial Biologics License Application approval of the amubarvimab/romlusevimab combination in December 2021,the Beijing Municipal Medical Products Administration is currently reviewing Brii Bio's Market Authorization Holder (MAH) inspection and application,a necessary step required for commercial sales of the amubarvimab/romlusevimab combination in China. Brii Bio is actively working with regulatory bodies in China to ensure Good Manufacturing Practice (GMP) certification of the amubarvimab/romlusevimab combination.The Company continues to work closely with its CDMO to assist in inspections by both U.S. FDA and China's provincial and municipal regulatory bodies.

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. NIH-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.

In December 2021,the amubarvimab/romlusevimab combination was approved by the National Medical Products Administration (NMPA) of China for the treatment in 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. In March 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.

In October 2021,the Company initiated and subsequently completed the rolling submission of an emergency use authorization (EUA) application with the U.S. Food and Drug Administration. In addition,the Company is pursuing additional efforts and regulatory filings for the amubarvimab/romlusevimab combination in established and emerging markets with an initial focus on securing access in countries where clinical trials were conducted and where significant gaps in access to highly effective treatments have been identified. The Company is planning further studies in China,to evaluate the use of the amubarvimab/romlusevimab combination among immunocompromised population as an additional measure of prophylaxis.

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.