The National Institutes of Health has halted its study of hydroxychloroquine, a drug President Donald Trump has promoted as a possible treatment for COVID-19 and once claimed to be taking himself.
In a statement issued on Saturday, the agency said that although it did not appear hydroxychloroquine caused harm to patients in the study, it was also "very unlikely to be beneficial."
"The data from this study indicate that this drug provided no additional benefit compared to placebo control for the treatment of COVID-19 in hospitalized patients," according to the NIH.
The announcement could represent the final judgement in the effort to determine whether the drug can be used to treat patients hospitalized with COVID-19, an illness that has infected more than 2.2 million Americans and which has claimed nearly 120,000 lives in the United States.
The Food and Drug Administration issued an emergency use authorization for the drug in March, a move that cleared the way for it to be tested as a possible treatment for the coronavirus. But the FDA revoked that authorization on Monday, saying it was "no longer reasonable to believe that oral formulations of [hydroxychloroquine] and [chloroquine] may be effective in treating COVID-19, nor is it reasonable to believe that the known and potential benefits of these products outweigh their known and potential risks."
On Wednesday, the World Health Organization followed suit, ending its trial of the drug as well.
The NIH launched its clinical trial of hydroxychloroquine in April at Vanderbilt University Medical Center in Nashville. It aimed to study a total of 500 patients, but the trial was stopped after 470 had been enrolled.
The drug has long been used to treat malaria and conditions such as arthritis and lupus. Early in the pandemic, researchers believed it carried the potential to also be effective against COVID-19. Laboratory tests showed the drug interfered with the ability of the coronavirus to enter cells, but those results came from relatively small tests that could never be replicated on a large scale.