For months, US President Donald Trump has promoted hydroxychloroquine as a potential Covid-19 treatment.
He has called the anti-malarial drug a "game changer", asked patients "what do you have to lose?" - and even announced he was taking the drug himself in an attempt to ward off the coronavirus.
This week, however, the World Health Organisation (WHO) announced it had temporarily halted its global trial of the drug, citing a new study which found a significantly higher risk of death among those taking hydroxychloroquine or the related drug chloroquine.
"The executive group has implemented a temporary pause of the hydroxychloroquine arm within the solidarity trial while the safety data is reviewed by the data safety monitoring board," said WHO director-general Tedros Adhanom Ghebreyesus.
Mr Trump, meanwhile, said he is no longer taking hydroxychloroquine, but again defended the drug as a Covid-19 treatment, pointing to "tremendous, rave reviews".
"I believe in it enough that I took a programme because I had two people in the White House that tested positive," he said, adding that his "two-week course" of the drug had recently finished.
"And by the way, I'm still here," Mr Trump added. "To the best of my knowledge, here I am."
The WHO's decision is the latest setback for backers of hydroxychloroquine, which has produced a series of disappointing results in scientific studies. In April, the US's Food and Drug Administration warned against using the drug outside of hospitals and clinical trials over reports of "serious heart rhythm problems" linked to the drug's use.
Last week, the medical journal 'Lancet' published a study of 96,000 hospitalised Covid-19 patients worldwide that found a 45pc increased risk of death and a 411pc increased risk of serious heart arrhythmias among those taking a cocktail of antibiotics and the anti- malarial drug.
"If there was ever hope for this drug, this is the death of it," said Eric Topol, a cardiologist and director of the Scripps Research Translational Institute in California.
The WHO started a clinical trial earlier this year to test hydroxychloroquine along with three other experimental treatments. Due to the findings published in the 'Lancet', Mr Ghebreyesus said the use of hydoxychloroquine in the trial, which now has more than 3,500 patients in 17 countries, will temporarily halt.
The trial will continue for the other three drugs, and the WHO will likely decide within the next two weeks whether to resume using hydroxychloroquine, said chief scientist Soumya Swaminathan.
At the weekend, Mr Trump continued to promote the drug. The president had revealed earlier this month he was taking hydroxychloroquine after one of his military valets and vice-president Mike Pence's press secretary, Katie Miller, tested positive for the coronavirus. Asked whether it was appropriate for him to take the drug despite the official warnings, the president stood by his decision.
"Well, I've heard tremendous reports about it. Frankly, I've heard tremendous reports. Many people think it saved their lives. Doctors come out with reports," he said, citing in particular an "incredible" study in France. A study by French researcher Didier Raoult which helped fuel initial enthusiasm for hydroxychloroquine has since been discredited by scientists.
Mr Trump added: "Hydroxy has had tremendous, if you look at it, tremendous, rave reviews." (© Washington Post)
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