The drug, tocilizumab, could save the lives of one in 25 coronavirus patients in hospital and reduce the need for ventilators in intensive care.
Researchers say around half of the people admitted to hospital with coronavirus could benefit from the treatment.
Scientists from the nationwide Recovery trial said when tocilizumab was given alongside the steroid dexamethasone, it reduced the absolute risk of mortality by four percentage points.
The medicine was already being used by the NHS to treat some coronavirus patients after early results last month showed it reduced the risk of death as well as time spent in hospital by up to 10 days.
As a result of the latest findings, the health secretary said the drug would be made more widely available on the NHS to help treat Covid patients.
It was found to reduce the relative risk of death by 14 per cent and cut the time spent in hospital by five days when used for patients on oxygen and in addition to the dexamethasone.
Martin Landray, professor of medicine and epidemiology at the University of Oxford, and joint chief investigator in the Recovery trial, said: “The results clearly show the benefits of tocilizumab and dexamethasone in tackling the worst consequences of Covid-19 – improving survival, shortening hospital stay, and reducing the need for mechanical ventilators.
“Used in combination, the impact is substantial. This is good news for patients and good news for the health services that care for them in the UK and around the world.”
More than 4,000 patients were involved in the Recovery trial, with 2,022 patients randomly allocated to receive tocilizumab, while the rest received standard care.
A majority of the patients, 82 per cent, were taking a steroid such as dexamethasone as part of the standard care.
The researchers found that 596 patients, 29 per cent, in the tocilizumab group died within 28 days, compared with 694, or 33 per cent, in the standard care group.
Tocilizumab also significantly reduced the chance of progressing to ventilation or death from 38 per cent to 33 per cent among those who were not on invasive ventilation when they started the trial.
According to the team, the results also suggest that, for patients who have significant inflammation and require oxygen, a combination of a steroid such as dexamethasone and tocilizumab cuts deaths by about a third for patients requiring simple oxygen, and nearly a half for those requiring ventilation.
Peter Horby, professor of emerging infectious diseases at the University of Oxford, and joint chief investigator for Recovery, said: “Previous trials of tocilizumab had shown mixed results, and it was unclear which patients might benefit from the treatment.
“We now know that the benefits of tocilizumab extend to all Covid patients with low oxygen levels and significant inflammation.
“The double impact of dexamethasone plus tocilizumab is impressive and very welcome.”
Last year, the trial found dexamethasone cut the risk of death by a third for patients on ventilators and by a fifth for those on oxygen.
Matt Hancock said: “Today’s excellent news is further proof the UK is at the forefront of the global mission to find safe and effective treatments for this terrible virus.
“I want to thank all those who have played a part in generating these tremendous results – from the British scientists and researchers behind the trial, to the thousands of patients who took part across the country.
“We are working quickly and closely with colleagues across the health system and sector to ensure every NHS patient who needs this treatment should be able to access it – reducing further pressures on the NHS and potentially saving thousands of lives.”
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