A drug championed by the US president as a possible cure for COVID-19 has been shown to provide no benefit and possibly a higher risk of death.
Hydroxychloroquine had been championed by Mr Trump after anecdotal reports that the drug, which is also used to treat lupus and rheumatoid arthritis, could help coronavirus patients.
However the new study found it might actually be harmful to those with the disease.
The American research analysed the records of 368 male patients with confirmed coronavirus.
They were all at veterans’ hospitals in the US and died or were discharged by 11 April, according to a version of the study posted online.
Some 28% of 97 patients given hydroxychloroquine and standard care died, while 22% of the 113 patients who were given hydroxychloroquine and antibiotic azithromycin died.
But the death rate among the 158 patients who received only standard care – without hydroxychloroquine – was 11%.
The study, which took patients’ individual characteristics into account, has not yet been accepted for publication in a medical journal but it has been submitted for expert review.
Hydroxychloroquine also appeared to have no effect on whether a patient needed breathing support: 13% of those who got the drug needed ventilation, versus 14% of those who received only supportive care.
Only 7% of those given the hydroxychloroquine and azithromycin needed help to breathe.
Dr Jeremy Falk, a pulmonary specialist at Cedars-Sinai Medical Center in Los Angeles, said the study was one of a few in the past few weeks to have placed doubt on whether hydroxychloroquine is beneficial.
Dr Falk, who was not involved in the study, said: “We were using it on just about everybody early on. Now we are using it more sparingly.”
There are no proven treatments for COVID-19, but hydroxychloroquine, an old malaria drug, has been getting a lot of attention after Mr Trump promoted it as a “game changer”.
“What do you have to lose? Take it,” he said earlier this month, adding that – while he has no medical or scientific training – his “common sense” qualified him to make such claims.
However, because of a lack of conclusive scientific studies, the US government’s top infectious disease specialist, Dr Anthony Fauci, had urged caution.