A new drug has been shown to save the lived of Covid-19 patients could represent  new lifeline for those most vulnerable to the virus, researchers have said.

The antibody combination developed by Regeneron was found in the Recovery trial to reduce the risk of death when given to patients with severe Covid who did not have a natural antibody response of their own.

The treatment uses a combination of two monoclonal antibodies, casirivimab and imdevimab, known as REGEN-COV in the US.

These bind specifically to two different sites on the coronavirus spike protein, neutralising the ability of the virus to infect cells.

Between 18 September 2020 and 22 May 2021, 9,785 UK patients admitted to hospital with Covid were randomly allocated to receive usual care plus the antibody combination treatment, or usual care alone.

Researchers found that among patients who received usual care alone, 28-day mortality was twice as high in those without an antibody response (30 per cent) compared with those (15 per cent) who had already developed natural antibodies against the virus.

For patients who had no antibody response, the treatment reduced the chance of them dying within 28 days by a fifth, compared with usual care alone, according to the study.

Researchers have said that for every 100 such patients treated with the antibody combination, there would be six fewer deaths.

The chances of these patients needing to be put on a ventilator were also reduced, as was the duration of their hospital stay.

However, researchers have said they are not sure when the treatment will be approved for use in the UK, and note that it will not be a quick rollout as the drug is not particularly easy to get hold of.

Patients would also need antibody testing on their admission to hospital, which is not currently in place.

The study will be published as a pre-print on medRxiv and submitted to a journal for peer-review.

'These results are very exciting'

Sir Martin Landray, professor of medicine and epidemiology at the Nuffield Department of Population Health, University of Oxford, and joint chief investigator for the Recovery trial said: “What we found was amongst these patients who were seronegative – they hadn’t raised antibodies of their own, if you then gave them this combination of two antibodies in an intravenous infusion, then mortality was reduced by one fifth.

“So instead of 30 per cent dying, 24 per cent died. So if you think of it differently, for every 100 patients who were given the intravenous infusion, we would save six lives.”

“Take a group of people, they’re sick, they go into hospital, they’ve got Covid, they haven’t got antibodies of their own, (this) will reduce their chance of dying, shorten their hospital stay, and reduce the chances of needing a ventilator," he added.

“So this is in some ways a first. This is an antiviral treatment that is used later on – because these patients are severe, they’ve gone into hospital – and has a demonstrated clear impact on survival, and on those other outcomes.

“So in its own right, it’s an important result because these patients are among the sickest patients, and here we now have a treatment we did not have before.”

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 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.”