Hydroxychloroquine does not benefit adults hospitalised with COVID-19, a new study by a major US research centre has found.
The National Institutes of Health (NIH) study sought to test whether the malaria and arthritis drug - which has long been touted by US President Donald Trump - works to treat coronavirus.
Between April and June, researchers randomly and equally divided shots of hydroxychloroquine and of a placebo to 479 coronavirus patients in 34 hospitals.
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Participants, who included 212 women as well as 290 Hispanic and Black people, were aged 57 on average.
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Health outcomes were assessed two weeks after their first dose.
This assessment found roughly 32% of the hydroxychloroquine group was able to return to normal lives compared with 29% of placebo participants.
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Just fewer than 48% of people from the former pool were discharged from hospital 28 days after starting treatment and only one per cent fewer in the latter group were released by the same date.
In each group, 25 people died.
Lead researcher of the ORCHID trial, Dr Wesley Self, concluded there were no major differences among samples.
"The finding that hydroxychloroquine is not effective for the treatment of COVID-19 was consistent across patient subgroups and for all evaluated outcomes, including clinical status, mortality, organ failures, duration of oxygen use, and hospital length of stay," the emergency medicine physician said.
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He also noted that the finding was consistent with similar trials in the United Kingdom and Brazil.
Another lead researcher, Dr Samuel Brown, said that while he had "hoped that hydroxychloroquine would help," the results were still an important step towards finding treatments that do work.
While several studies have yielded different results on whether the drug works as a prevention or treatment for COVID-19, the NIH study has declared the strongest findings yet on its ineffectiveness.
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In May, Mr Trump revealed he had been taking it to stave off the infection. After catching the virus months later, he said it was also an ingredient in his "cocktail of treatment".
America's top infectious disease expert Dr Anthony Fauci earlier highlighted clinical studies concluding the drug is not proven to successfully treat the virus - including research commissioned by the World Health Organisation and the NIH.
The Food and Drug Administration initially approved emergency use of the drug for coronavirus treatment but revoked the move in June, saying its unproven benefits "do not outweigh the known and potential risks", including reports of heart complications.
