Brii Biosciences Receives Clinical Hold Notification from US. FDA on BRII-732

DURHAM, N.C., United States and BEIJING, China – December 12, 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 need and large public health burden, today announced that the Company receives notification from the U.S. Food and Drug Administration (FDA) to place a clinical hold on Company’s phase 1 clinical study that evaluates BRII-732 safety in healthy volunteers.

This clinical hold on the phase 1 study was requested by FDA as part of the agency’s decision to temporarily hold islatravir-based clinical studies, a drug candidate under development by Merck (known as MSD outside of the U.S. and Canada) to allow the agency to better understand the safety profile of the molecule. BRII-732 is a proprietary prodrug of islatravir developed by the Company. The phase 1 clinical study of BRII-732 was on-going without any significant safety signals observed before it is requested to be put on hold. There are no subjects currently receiving BRII-732.

“The clinical hold was not triggered by any signal observed in our study, nor on pre-clinical data with BRII-732.” stated David Margolis, M.D., MPH., Vice President and Head of Infectious Diseases Therapy Area at Brii Bio. “However, FDA decided to take precautionary measures to temporarily hold clinical studies involving islatravir and further investigate the findings. Patient safety is paramount, and we will work closely with FDA to fully investigate this finding and determine the development path forward for BRII-732. We would like to thank the volunteers as well as the investigators and site personnel that have participated in this study and remain positive about the potential for BRII-732 to provide a simplified dosing option for patients living with HIV, once dosing resumes”

About BRII-732

BRII-732, a prodrug of 4’-ethynyl-2-fluoro-2’-deoxyadenosine (EFdA), is a potent human immunodeficiency virus (HIV)-1 nucleoside reverse transcriptase translocation inhibitor (NRTTI). EFdA can be metabolized to the active metabolite, EFdA-triphosphate (EFdA-TP). EFdA-TP exerts its antiviral activity through acting not only as a potent chain-terminator like the approved nucleoside reverse transcriptase inhibitors (NRTIs), but also as a translocation inhibitor of HIV-1 reverse transcriptase by blocking translocation of nascently synthesized strand for the next nucleotide incorporation.  BRII-732 is currently in Phase 1 clinical development, with potential for once-weekly oral dosing.

About Islatravir

Islatravir (MK-8591) is Merck’s investigational nucleoside reverse transcriptase translocation inhibitor under evaluation in more than 10 clinical trials. For treatment, islatravir was being evaluated in combination with other antiretrovirals. It was also being studied for pre-exposure prophylaxis (PrEP) of HIV-1 infection as a single agent across a variety of formulations, including an oral once-monthly regimen.

Merck recently announced to pause the enrollment for a phase 2 study evaluating an oral weekly combination regimen of islatravir and another investigational agent for HIV treatment, as well as two phase 3 study evaluating once-monthly, oral islatravir for pre-exposure prophylaxis (PrEP) of HIV-1 infection. More announcements may be forthcoming.

About Brii Biosciences

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

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Darcie Robinson (US)

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