LONDON (Reuters) – Britain will provide the anti-viral drug remdesivir to certain COVID-19 patients that it is most likely to benefit as part of a collaboration with manufacturer Gilead Sciences, the health ministry said on Tuesday.

The department of health said early data from clinical trials around the world showed that the drug could shorten the recovery time of COVID-19 patients by four days.

“This is probably the biggest step forward in the treatment of coronavirus since the crisis began,” health minister Matt Hancock told a government news conference.

“These are very early steps, but we are determined to support the science and back the projects that show promise.”

The government said the allocation of the drug would be determined by where it would have the greatest benefit, but did not say how many patients would be treated.

The U.S. National Institutes of Health (NIH) said last week that data from its trial of remdesivir showed that the drug offers the most benefit for COVID-19 patients who need extra oxygen but do not require mechanical ventilation.

The researchers also said that “given high mortality despite the use of remdesivir,” it is likely that the drug would be more effective in combination with other treatments for COVID-19, the respiratory illness caused by the novel coronavirus.

Stephen Griffin, an associate professor at Leeds University, welcomed the move to use remdesivir, saying it would “likely mean that the most severe COVID-19 patients will receive it first”. He said that while this approach was the most ethical, it also meant drug would not be a “magic bullet”.

“We can instead hope for improved recovery rates and a reduction in patient mortality,” Griffin said.

Gilead said it expects results from its own study of remdesivir in patients with moderate COVID-19 at the end of this month.

(Reporting by Alistair Smout, Kate Holton and Kate Kelland; editing by Guy Faulconbridge and Stephen Addison)