Regeneron’s COVID-19 Antibody Cocktail Reduces Death by 20%

Regeneron recently announced that its COVID-19 antibody cocktail, REGEN-COV, reduced risk of death by 20 percent in patients hospitalized with COVID-19 who had not mounted their own immune response (seronegative), compared to standard care on its own. 

The Phase 3 UK RECOVERY trial enrolled 9,785 patients hospitalized with COVID-19 between September 2020 and May 2021. Patients received 8,000 milligrams of REGEN-COV or standard care. 

Researchers found that 24 percent of patients in the REGEN-COV group died, compared to 30 percent of patients in the standard care group. Additionally, there was no longer a significant effect on 28-day mortality when combining the larger seropositive group with the seronegative group. 

Notably, RECOVERY is the first trial large enough to definitively determine whether REGEN-COV reduces mortality in patients hospitalized with severe COVID-19.

"The hope was that by giving a combination of antibodies targeting the SARS-CoV-2 virus we would be able to reduce the worst manifestations of COVID-19," Sir Peter Horby, professor of emerging infectious diseases in the Nuffield Department of Medicine at the University of Oxford and joint chief investigator of the RECOVERY trial, said in the announcement. 

"There was, however, great uncertainty about the value of antiviral therapies in late-stage COVID-19 disease. It is wonderful to learn that even in advanced COVID-19 disease, targeting the virus can reduce mortality in patients who have failed to mount an antibody response of their own,” Horby continued. 

In previous Phase 3 trials of hospitalized COVID-19 patients, REGEN-COV reduced viral levels, shortened time to resolution of symptoms, and significantly reduced risk of hospitalization or death. 

In a November Phase 2/3 clinical trial, the antibody cocktail reduced viral load and patient medical visits, including hospitalization, emergency room, urgent care visits, and physician office or telemedicine visits. 

Treatment with the antibody cocktail reduced medical visits related to COVID-19 by 57 percent through day 29 and reduced related medical visits by 72 percent in patients with one or more risk factor.

Based on trial results, RECOVERY focused on seronegative patients. 

Patients in RECOVERY who received usual care alone had double the mortality rate at day 28 if they were seronegative (30 percent) compared to seropositive (15 percent). 

The median duration of hospital stay was four days shorter among seronegative patients in the REGEN-COV group than in the usual care group. The proportion of patients discharged alive by day 28 was greater, at 64 percent versus 58 percent, respectively. 

A recent publication in Cell found that REGEN-COV retains potency against the main variants of concern in the US, including P.1, first identified in Brazil, B.1.351, first identified in South Africa, and B.1.162.2, first identified in India. 

The combined frequency of the P.1 and B.1.351 variants now exceed 10 percent of new COVID-19 diagnoses across eight states, a Regeneron spokesperson highlighted. 

"The trial was conducted at a time when most patients had not been fully vaccinated. These results provide hope to patients who have a poor immune response to either the vaccine or natural infection, as well as those who are exposed to variants for whom their existing antibodies might be sub-optimal,” said David Weinreich, MD, executive vice president of global clinical development at Regeneron.

In August, Roche and Regeneron partnered to develop, manufacture, and distribute REGEN-COV. Regeneron is responsible for development and distribution of the antibody in the US, while Roche is responsible for development and distribution outside the US. 

At the end of November, FDA issued an emergency use authorization to REGEN-COV. 

Currently, Regeneron is in discussions with FDA to expand the authorization to other populations, including the prevention and hospitalized patient settings. And later this year, the company expects to submit a biologics license application for REGEN-COV.