More than two-thirds of severely ill COVID-19 patients saw their condition improve after treatment with the antiviral remdesivir, an experimental drug being developed by US drug firm Gilead Sciences, according to a study.

The observational cohort analysis does not detail what other treatments the 61 hospitalised patients were given and data on eight of them were not included — in one case, because of a dosing error.

The US author of the paper published in the New England Journal of Medicine called the findings “hopeful”.

But cautioned that it was difficult to interpret the results since they did not include a comparison to a control group.