Brii Biosciences’s discontinued antibody treatment combination provided a strong protective effect in high-risk people with early Covid-19 symptoms, researchers reported.

The antibody combo was investigated in a large international Phase II/III platform trial (NCT04518410) that enrolled 4,044 outpatients with Covid-19 infections, sponsored by the National Institute of Allergy and Infectious Diseases (NIAID). The study investigated the safety and effectiveness of different drugs.

Also known as BRII-196/198, the combination of amubarvimab and romlusevimab portion of the platform trial enrolled more than 800 non-hospitalised patients with Covid-19 who were at a high risk of disease progression in the US, Argentina, Brazil, Mexico, the Philippines, and South Africa.

This part of the trial was co-led by investigators at Weill Cornell Medicine College and New York-Presbyterian Hospital in the US.

The recently announced data showed participants who were treated by the antibody treatment duo had a 2.3% rate of progression to hospitalisation or death compared to 10.7% in the placebo group.

BRII-196/198 was also as effective in patients that enrolled six to ten days after symptom onset compared with patients who enrolled earlier. The safety analysis showed that the number of treatment-related side effects was significantly reduced in the treatment group compared to the placebo arm.

BRII-196/198 is a combination of two non-competing SARS-CoV-2 monoclonal neutralising antibodies obtained from convalesced Covid-19 patients. The antibody combo was co-developed Brii Bio, Tsinghua University and the Third People’s Hospital of Shenzhen.

In December 2021, China approved BRII-196/198 as a treatment for adults and granted conditional approval for the paediatric population aged 12 to 17 years old. Brii Bio filed an emergency use authorization (EUA) with the FDA in October 2021 but it was never approved for use.

In March 2023, the biotech announced the discontinuation of the antibody combo and stopped manufacturing efforts in order to redirect resources to other programmes. The decision was based on the constantly evolving Covid-19 trends and “protracted regulatory inspections” at the CDMO sites.

Brii Bio noted that the discontinuation decision was also influenced by the expiration of the federal public health emergency (PHE). The end of PHE was announced by US President Joe Biden’s administration at the end of January.

The Covid-19 emergency will end in May 2023. As a result, many Americans may not be able to access free Covid-19 tests, vaccines, and therapeutics. It also poses a risk to the planned Covid-19 trials. As of February 2023, there were more than 650 industry-sponsored trials, with most still in early phases.