The idea is to inject these artificial antibodies so that they bind to the virus in an attempt to stop the infection in its tracks.
The therapy uses two artificial antibodies, these are generated in the laboratory to make very strong antibodies.
These two monoclonal antibodies, casirivimab and imdevimab, bind specifically to two different sites on the coronavirus spike protein, neutralizing the ability of the virus to infect cells.
Because this treatment uses two types of artificial antibodies, it is hoped that it will be able to bypass any resistance the patient develops against any of them. It is also hoped that by using a combination of antibodies, the likelihood of viral variants escaping treatment is reduced.
Trial with UK patients
Between September last year and May 22, 9,785 UK patients admitted to hospital with the disease were randomly assigned to receive usual care plus combination antibody therapy, or usual care alone.
The trial demonstrated that the combination of antibodies developed by Regeneron reduced the risk of death when given to patients with severe Covid-19, who had not developed their own natural antibody response.
The chances that these patients would need to be put on a ventilator were also reduced, as was the length of their stay in hospital.
Of these, about a third were HIV negative, meaning they had no natural antibody response, and half were HIV positive, meaning they had already developed natural antibodies against the virus.
For a sixth of those involved in the study, their HIV status was unknown.
The researchers found that among patients who received usual care alone, the 28-day mortality was twice as high among those without an antibody response (30%) than among those who were HIV-positive (15 percent) at the start of treatment. study.
According to the study, for patients who did not have an antibody response, treatment reduced the risk of death within 28 days by a fifth, compared to usual care alone.
For 100 of those patients treated with the combination of antibodies, there would be six fewer deaths, according to the researchers.
“What we found was among those patients who were HIV negative – they hadn’t produced antibodies themselves, if you then gave them this combination of two antibodies in an intravenous drip, the mortality was reduced by a fifth. Sir Martin Landray explained. , Professor of Medicine and Epidemiology in the Nuffield Department of Population Health, University of Oxford, and Joint Chief Investigator.
“So instead of 30 percent dead, 24 percent died. So if you think of it differently, for every 100 patients who received the intravenous infusion, we would save six lives, ”he added.
“Take a bunch of people, they are sick, they go to the hospital, they have Covid, they don’t have antibodies of their own, (this) will reduce their chances of dying, shorten their stay in the hospital and reduce the chances of needing a ventilator.
“So this is sort of a first. It’s an antiviral treatment that’s used later – because these patients are severe, they went to the hospital – and has a clear impact on survival and those other outcomes, ”Landray said.
“So in itself that’s an important result because these patients are some of the sickest patients, and here we now have a treatment that we didn’t have before. “
For HIV negative patients who received treatment, the length of hospital stay was four days shorter than the usual care group, and the proportion of patients discharged alive on day 28 was higher (64% vs. 58%) .
The treatment made no difference in patients who had developed their own antibody response by the time the study began, the researchers found.
Sir Peter Horby, Professor of Emerging Infectious Diseases in the Nuffield Department of Medicine, University of Oxford, and Joint Chief Investigator for the Recovery trial, said: “These results are very exciting.
“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. There was, however, great uncertainty about the value of antiviral therapies in the advanced stage of Covid-19 disease, ”he explained.
“It’s wonderful to learn that even in advanced cases of Covid-19 disease, targeting the virus can reduce mortality in patients who have failed to develop their own antibody response. “
The researchers say they don’t know when the treatment will be approved for use in the UK, and point out that it won’t be a rapid rollout because the drug isn’t particularly easy to obtain, and patients would need to antibody tests upon admission to hospital – which is not currently in place.
The study will be published as a pre-print on medRxiv and submitted for peer review.
The treatment uses a combination of two monoclonal antibodies (casirivimab and imdevimab, known as REGEN-COV in the US) that specifically bind to two different sites on the coronavirus spike protein, neutralizing the virus’s ability to infect cells.
Previous studies in patients in the community have shown that treatment reduced viral load, shortened the time to symptom resolution, and significantly reduced the risk of hospitalization or death.