Brii Bio Initiates Submission of Emergency Use Authorization Filing to U.S. FDA for BRII-196/BRII-198, its Monoclonal Antibody Combination Therapy for Non-Hospitalized COVID-19 Patients at High Risk of Clinical Progression to Severe Disease

DURHAM,N.C. and BEIJING,Oct. 9,2021 -- 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 needs and large public health burdens,today announced the filing of an emergency use authorization (EUA) application for its investigational SARS-CoV-2 (virus that causes COVID-19) combination therapy,BRII-196/BRII-198 ("combination BRII-196/BRII-198") with the U.S. Food and Drug Administration (FDA).Data to support the EUA filing will be submitted by the Company to the U.S. FDA on a rolling basis.

The EUA filing is based on positive results from the NIH-sponsored Phase 3 clinical trial,ACTIV-2,in which the BRII-196/BRII-198 combination demonstrated a statistically significant 78% reduction of hospitalization and death and improved safety 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. This analysis also showed zero deaths in the treatment arm versus eight deaths in the placebo arm through day 28. There was one death in each arm during the post 28-day follow up. Following completion of the EUA submission,review and approval,Brii Bio plans to work closely with the FDA to coordinate on the next steps for full regulatory approval of combination BRII-196/BRII-198.

"We are very pleased with the continued positive clinical outcomes and favorable safety profiles throughout the development of BRII-196/BRII-198 in this well designed and executed global clinical trial,and we intend to bring this potential new treatment option,supported by the strong clinical evidence,to a broad range of COVID-19 outpatients at high risk of clinical progression," said Zhi Hong,Ph.D.,Chairman and CEO of Brii Bio. "If authorized for emergency use,we are well positioned to accelerate manufacturing of BRII-196/BRII-198 as quickly as possible in order to supply the ongoing demand for the treatment of non-hospitalized COVID-19 patients at high risk of clinical progression throughout the U.S."

In addition,the Company is pursuing additional efforts and regulatory filings for combination BRII-196/BRII-198 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. Investigational New Drug (IND) applications have been submitted by the Company and approved for the combination therapy to the U.S. FDA,the China National Medical Products Administration (NMPA) and the Department of Health in Hong Kong,China. The Company 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 lower dose combination BRII-196/BRII-198 for the treatment of COVID-19.

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.

About Phase 3 ACTIV-2

BRII-196/BRII-198 is a SARS-CoV-2 neutralizing monoclonal antibody combination therapy. Interim results from Phase 3 of the NIH-sponsored ACTIV-2 trial recently demonstrated that the combination therapy achieved a statistically significant reduction,78%,of relative risk in the combined endpoint of hospitalization and death in non-hospitalized COVID-19 patients at high risk of clinical progression (nominal one-sided p value = 0.00001). Of those subjects who received treatment with BRII-196/BRII-198 within five days of symptom onset,2% (4/196) progressed to hospitalization or death,compared with 11% (21/197) in the placebo arm. Similarly,2% (5/222) of subjects who received treatment with BRII-196/BRII-198 at six to 10 days following symptom onset progressed to hospitalization or death,compared with 11% (24/222) of those receiving placebo. Grade 3 or higher adverse events (AEs) were less common in the BRII-196/BRII-198 treatment arm versus placebo,3.8% (16/418) versus 13.4% (56/419),with no drug related severe adverse events (SAEs) or infusion reactions observed. Following the clear demonstration of both clinical and safety outcomes,the independent data safety monitoring board (DSMB) permitted the early release of the interim results while the complete study follow-up remains ongoing.

This study was conducted at clinical trial sites around the world,including the U.S.,Brazil,South Africa,Mexico,Argentina and the Philippines,with patients enrolled 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),B.1.617.2 (Delta),B.1.429 (Epsilon),P.1 (Gamma),C.37 (Lambda),and B.1.621 (Mu).

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,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.

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