Brii Biosciences Presents Promising Clinical Data to Support Ongoing Development of Novel HIV Therapeutic Candidates at IDWeek 2022

Findings from two Phase 1 studies show both BRII-732 and BRII-778 are safe and well-tolerated

Results indicate potential for oral once-weekly,long-acting combination therapy for HIV infection,supporting continued clinical development

Additional data presented by Brii's licensing partners at IDWeek 2022 showcase breadth of Company's infectious disease program,spanning six therapeutic candidates and four potential disease indications

DURHAM,N.C. and BEIJING,Oct. 19,2022 --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 from two Phase 1 studies in healthy volunteers in the U.S.,which evaluated long-acting BRII-732 and BRII-778,both drug candidates in development for the treatment of human immunodeficiency virus (HIV) infection. Results from both studies show that once-weekly BRII-732 and BRII-778 are safe and well-tolerated,generating important data to support the ongoing development of a potential first-in-class oral once-weekly combination therapy to treat HIV. The findings from these studies were presented in two poster sessions at IDWeek 2022.

One of the posters presented at IDWeek titled,Safety,Tolerability,and Pharmacokinetics of BRII-732,A Medoxomil Carbonate Prodrug of Islatravir in Healthy Adult Subjects,highlights that oral BRII-732 demonstrated an acceptable safety and tolerability profile following single ascending dose (SAD) up to 200 mg and multiple ascending dose (MAD) up to 25 mg,as well as a favorable and linear pharmacokinetic (PK) profile that achieved therapeutic targets. These data reinforce potential development of BRII-732 as part of a combination antiretroviral therapy,inclusive of once-weekly dosing.

"Our HIV research program aims to advance the standard of care for the more than 38 million people living with HIV around the world,many of whom desire new treatment options that enable more convenient administration while also helping to manage this lifelong infection," said Ji Ma,Ph.D.,Vice President of Preclinical Development and Clinical Pharmacology at Brii Bio. "These findings illustrate the potential for BRII-732 and BRII-778 to become a safe and well-tolerated,novel treatment regimen for patients that may help to ease the burden of daily medications and even minimize social stigma that many people living with HIV currently face. We look forward to progressing the clinical development of both compounds,BRII-732 and BRII-778,into the next stage of studies as we work to advance a first-of-its-kind investigational oral long-acting combination treatment option for patients."

A second poster at IDWeek titled,and Pharmacokinetics of BRII-778,A Modified-Release Oral Formulation of Rilpivirine in Healthy Adult Subjects,demonstrates that SAD and MAD administration of BRII-778 formulations are generally safe and well-tolerated with PK profiles consistent with slower oral absorption,providing key insights for ongoing clinical evaluation and development of BRII-778 as part of a potential once-weekly regimen for the treatment of HIV.

In addition,three of the Brii's strategic development partners are presenting a total of 16 abstracts at IDWeek 2022 related to assets under co-development with the Company. This collective presence at IDWeek underpins the robust scientific progress across Brii's anti-infectives portfolio designed to tackle a broad range of infectious diseases that present significant public health burdens to people around the world. As part of these partnerships,Brii holds licensing rights to advance multiple therapeutic candidates in Greater China for multi-drug resistant (MDR) and extensive drug resistant (XDR) gram-negative infections with Qpex Biopharma,as well as non-tuberculosis mycobacteria with AN2 Therapeutics.

"This robust set of data from Brii's HIV program as well as our partnered assets in MDR/XDR antibiotics not only highlight the Company's expertise and leadership across the infectious disease space,but also demonstrate our commitment to developing unique therapeutic solutions for diseases that present significant—and in some cases rapidly growing—medical needs for patients and healthcare providers alike," said David Margolis,M.D.,MPH,Head of Infectious Diseases Therapy Area at Brii Biosciences. "As we continue our work to bridge the gap between scientific breakthroughs and patients' needs,we are committed to innovating new therapeutic candidates for some of the world's most common illnesses,including HIV,where current oral treatment options are limited to life-long daily dosing,which is considered problematic and disruptive to daily life by many people living with HIV."

The posters presented at the meeting can be accessed online by registered attendees via the interactive program site.

About BRII-732/BRII-778 Combination

BRII-732/BRII-778combination is currently in Phase 1 development in the U.S. as therapy for human immunodeficiency virus (HIV) infection that can be administered on weekly basis – a potentially preferable choice for patients currently receiving once-daily treatment for HIV. This therapeutic combination offers three distinct and comprehensive mechanisms of action – non-nucleoside reverse transcriptase inhibitor (NNRTI),nucleoside reverse transcriptase inhibitors (NRTI),and nucleoside analogue reverse transcriptase translocation inhibitor (NRTTI) – to potentially treat HIV-1 as a complete treatment regimen. BRII-732 is a new chemical entity (NCE) that,upon oral administration,is a proprietary prodrug that is metabolized into the active moiety islatravir,an investigational candidate being studied to treat and prevent HIV infection,which functions as both a potent NRTI and a NRTTI. BRII-778 is an extended-release formulation of rilpivirine hydrochloride,an FDA-approved instant-release NNRTI,which has exhibited antiviral activity against a broad panel of HIV-1 isolates. BRII-778 has been formulated as a modified release oral tablet to enable once-weekly dosing.

The Company is working closely with the U.S. Food and Drug Administration to align its understanding of the CD4+ safety signal identified in the islatravir-related studies and to address the current clinical holdwith BRII-732,including resumed dosing and development of our once-weekly oral combination of BRII-732 and BRII-778.

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 worldwide. For more information,visit www.briibio.com.