Brii Biosciences Provides Update on Strategic Clinical Development Progress

Topline Phase 2 data from multiple hepatitis B viral (HBV) infection functional cure combination studies expected in the first half of 2023

Initiation of Phase 2 postpartum depression (PPD) study planned for early 2023 to advance potential first-of-its-kind treatment

U.S. FDA lifted clinical hold on BRII-732 allowing the Company to reinitiate a clinical trial to investigate a lower once-weekly oral dose,intended for the treatment and prevention of HIV infection

DURHAM,N.C.,and BEIJING,Dec. 27,2022 -- Brii Biosciences Limited ("Brii Bio" or the "Company",stock code: 2137.HK),a biotechnology company developing therapies to improve patient health and choice across diseases with high unmet need,today announced progress against its strategic clinical development priorities,including various updates across its pipeline of infectious disease and central nervous system disease candidates.

"We continue to progress clinical development of our two lead pipeline programs for a novel functional cure for hepatitis B viral infection in China and a potential first-of-its-kind treatment for postpartum depression in the U.S.," said Zhi Hong,Ph.D.,Chairman and Chief Executive Officer of Brii Bio. "These recent advancements in HBV and PPD provide a sharper focus for our China and U.S. teams,respectively,and further exemplify our differentiated approach to pursue curative or single treatment options in two large and important disease areas. We look forward to continuing to foster strategic collaborations and harness our proven development capabilities as we advance our pipeline of therapeutic candidates for patients."

Updates to Brii Bio's Lead Clinical Programs

Hepatitis B Virus (HBV)

Brii Bio is building a novel and first-in-class clinical portfolio of HBV therapeutic candidates alongside our strategic partners that may be used in various combinations to improve the probability of achieving a high rate of functional cure for each subpopulation of HBV patients in China. While HBV is one of the world's most significant infectious disease threats,China has the largest prevalence of HBV in the world,with 87 million people impacted by this disease.

Patients have completed treatment in Brii Bio's ongoing Phase 2 multi-regional clinical trial (MRCT) combination study of BRII-179 (VBI-2601) and BRII-835 (VIR-2218). The abstract highlighting the interim safety and efficacy data from this study has been accepted for oral presentation at the 32nd Conference of the Asian Pacific Association for the Study of the Liver (APASL),taking place in Taipei,Taiwan,from February 15-19,2023.

In December,the Company completed patient enrollment in part one of a Phase 2 combination trial evaluating the addition of BRII-179 (VBI-2601) in chronic HBV patients already receiving pegylated interferon alpha (PEG-IFN-α) and nucleotide/nucleoside reverse transcriptase inhibitors (NRTI) treatment. Topline results are expected in the third quarter of 2023.

Brii Bio's strategic development partner,Vir Biotechnology,shared preliminary data from an ongoing Phase 2 trial of combination BRII-835 (VIR-2218) with PEG-IFN-α,which demonstrated that approximately 30% of patients with chronic HBV infection achieved HBsAg seroclearance with anti-HBs seroconversion by the end of treatment with no new safety signals. The results were presented in an oral session at the American Association for the Study of Liver Diseases (AASLD) The Liver Meeting®.

Initial data from Part B of Vir's ongoing Phase 2 MARCH trial are expected in the second half of 2023 and will evaluate BRII-835 (VIR-2218) and BRII-877 (VIR-3434) together and in triple combination with PEG-IFN-α,including determining dose and length of treatment.

Postpartum Depression (PPD)

Brii Bio is developing BRII-296 as a first-of-its-kind one-time injection therapeutic candidate with the potential to expand the PPD treatment landscape for patients in the U.S.,where one in seven new mothers are impacted by this condition.

Brii Bio recently participated in a Type C meeting with the U.S. Food and Drug Administration (FDA) at which it received productive feedback and guidance regarding the Company's Investigational New Drug (IND) application for BRII-296. Following this discussion,Brii Bio is preparing to initiate its Phase 2 study of BRII-296 for the treatment of PPD in early 2023.

In September,Brii Bio announced positive topline results from its Phase 1 study of BRII-296 with data that demonstrated a single administration of the investigational therapy at 600 mg delivered a favorable pharmacokinetic profile and was safe and well-tolerated in healthy subjects. Furthermore,early feedback from physicians and patient communities are very positive and reinforce the potential for a first-of-its-kind single-injection treatment option for PPD.

Additional Pre-Clinical and Clinical Development Updates

Human Immunodeficiency Virus (HIV) Infection

Based on pharmacokinetic (PK) data from a completed Phase 1 study,Brii Bio has made the decision to discontinue development of BRII-778,which was being evaluated as part of a potential long-acting combination therapy for HIV infection. The Company is exploring partnership opportunities to continue developing BRII-732 as part of a potential oral,once-weekly,long-acting combination treatment option for HIV-1 patients.

In October,Brii Bio presented positive Phase 1 data showing that BRII-732 demonstrated an acceptable safety and tolerability profile,as well as a favorable and linear PK profile that achieved therapeutic targets in healthy volunteers,reinforcing its potential as an once-weekly oral therapy for the treatment and prevention of HIV infections.

Brii Bio recently received notification that the U.S. FDA has lifted the clinical hold on the Company's planned Phase 1 study to investigate a lower oral dose of once-weekly BRII-732.

MDR/XDR Gram-Negative Bacteria Infections

BRII-672 has the potential to be the first oral treatment option for complicated urinary tract infections (cUTI) targeting gram-negative bacteria resistant to carbapenem. In December 2022,the first pre-IND was submitted to the National Medical Products Administration (NMPA) seeking regulatory guidance around a development plan for BRII-672 in China.

BRII-693 has a highly differentiated safety and efficacy profile to address the most difficult-to-treat Acinetobacter baumannii and Pseudomonas aeruginosa infections resistant to carbapenem. Brii Bio plans to submit a pre-IND to the China NMPA in the first quarter of 2023.

Preclinical data and interim Phase 1 clinical results for BRII-636,BRII-672 and BRII-693 were presented at IDWeek in October 2022.

Nontuberculosis Mycobacteria (NTM) Lung Disease

Brii Bio's strategic partner,AN2 Therapeutics,expects to complete enrollment in the Phase 2 part of the pivotal Phase 2/3 clinical trial evaluating BRII-658 (epetraborole) for treatment-refractory lung disease caused by Mycobacterium avium complex (MAC) in mid-2023 and plans to begin enrollment of the Phase 3 portion of the trial immediately thereafter.

COVID-19

Following the Company's commercial launch of the amubarvimab/romlusevimab combination in China,the long-acting COVID-19 neutralizing antibody therapy is being used to treat patients in China,and early feedback from physicians has been positive.

Based on ongoing preclinical testing,the amubarvimab/romlusevimab combination retains neutralizing activity against the major SARS-CoV-2 subvariants currently circulating in China,underscoring the antibody combination as an important treatment option for high risk patients in China.

About Brii Bio

Brii Biosciences is a biotechnology company developing therapies to address some of the world's most common diseases where patients experience high unmet medical needs,limited choice and significant social stigmas. With a focus on infectious and central nervous system diseases,the Company is advancing a broad pipeline of unique therapeutic candidates with lead programs to develop a novel functional cure for hepatitis B viral infection (HBV) and a first-of-its-kind treatment for postpartum depression (PPD). The Company is led by a visionary and experienced leadership team and has operations in key biotech hubs,including Raleigh-Durham,the San Francisco Bay Area,Beijing and Shanghai. For more information,visit www.briibio.com.