The study found that hydroxychloroquine, which President Donald Trump has frequently touted a possible treatment, did not provide any benefit to the patients, even though it did no harm, NIH said in a statement.

Earlier this week, the World Health Organization said testing of hydroxychloroquine in its large multi-country trial of treatments for Covid-19 patients had been halted after new data and studies showed no benefit.

The US Food and Drug Administration revoked its emergency use authorisation for hydroxychloroquine to treat Covid-19 on Monday.

Trump had promoted the drug as a potential treatment, saying in March it could turn out to be “one of the biggest game-changers in the history of medicine” when used in combination with the antibiotic azithromycin.

Last month, in a surprise announcement, Trump said he was taking a course of hydroxychloroquine as a preventative after two White House aides tested positive for the novel coronavirus that causes Covid-19.

NIH announced its trial of hydroxychloroquine, which is used to treat malaria and rheumatoid conditions such as arthritis, in April.