The world's largest randomised trial of potential medicines for Covid-19 is to add Regeneron's experimental antiviral antibody cocktail REGN-COV2 to the drugs it is testing in patients hospitalised with the disease.
The UK RECOVERY trial, which has been testing a range of potential Covid-19 treatments since it began in April, will compare the effects of adding REGN-COV2 - a lab-manufactured monoclonal antibody - to standard care.
"This is the first drug actually designed for this disease," said Martin Landray, a professor of medicine & epidemiology at Oxford University who is co-leading the trial.
"There are lots of good reasons for thinking this might be really quite a powerful treatment," he told Reuters in an interview.
The addition of Regeneron's drug to the RECOVERY trial comes amid growing hopes that monoclonal antibodies may emerge as effective ways to treat Covid-19.
Until now, the RECOVERY trial had mostly been studying whether existing drugs could be re-purposed to tackle the new disease, and it has already found answers on a number of them.
In June and September, trial results showed that widely used steroids such as dexamethasone and hydrocortisone were able to reduce death rates among severely-ill Covid-19 patients
Also in June, RECOVERY trial results showed that the anti-malarial drug hydroxychloroquine, once touted by US President Donald Trump as a potential "game changer" in the pandemic, was of no benefit in treating Covid-19 patients.
Regeneron's REGN-COV2 cocktail, which the company is already testing in late-stage clinical trials in people, combines one Regeneron-made antibody and a second antibody isolated from people who have recovered after being infected with Covid-19.
The combination is designed to bind to the spike protein used by the new coronavirus to gain access to human cells, limiting the virus's ability to escape.
Regeneron developed the biological drug before linking up with Roche to expand its manufacturing capacity in hopes of meeting global demand, should the medicine prove effective. Regeneron would handle US sales, with Roche selling the medicine around the world.
Landray said his team had secured enough supply of the drug so that up to "several thousand" patients could be given it in the trial and compared with several thousand controls.
"Given that the second phase (of Covid-19 infections in the UK) seems to be coming now, it is a really good time to be starting this," he said.
The United States already has a $450 million deal for the cocktail in place, under the terms of which Regeneron will sell it around 70,000 to 300,000 potential treatment doses or 420,000 to 1.3 million prevention doses of REGN-COV2. Data is due later this month, Regeneron has said.
Alongside Regeneron, Eli Lilly, working with biotech firm AbCellera, is seen as a leading contender in the antibody race. In August it started testing whether its antibody can prevent Covid-19 infections in nursing homes. A separate trial testing the compound on recently diagnosed Covid patients may yield initial data in September or shortly after.
GlaxoSmithKline and partner Vir Biotechnology also began testing an experimental antibody on newly diagnosed Covid-19 patients late last month.
AstraZeneca is for now testing its antibody-based cocktail on healthy volunteers for tolerability.