The malaria drug, hydroxychloroquine, was ineffective in preventing infection in people exposed to coronavirus, a clinical trial released on Wednesday said.
The study was conducted on 821 people by researchers from the University of Minnesota and Canada.
The study is the first large controlled clinical trial of hydroxychloroquine conducted after the malaria drug was promoted by U.S. President Donald Trump as a treatment for COVID-19.
In March, Mr Trump repeatedly promoted the drug saying he had recently taken it himself.
He said hydroxychloroquine, used in combination with the antibiotic azithromycin, had “a real chance to be one of the biggest game-changers in the history of medicine,” with little evidence to back up that claim.
He later said he took the drugs as a preventive measure after two people who worked at the White House were diagnosed with COVID-19, the illness caused by the coronavirus.
But the latest report from Canadian researchers said the drug has no proven potency against coronavirus after hundreds of patients were evaluated.
It came as two leading American medical research publications retracted a study that claimed chloroquine was both ineffective and fatal to Covid-19 patients.
Four medical experts had authored the controversial findings in the New England Journal of Medicine and The Lancet, drawing widespread skepticism from other experts who said the fatality claim was a new dimension that should be thoroughly investigated for accuracy.
But after the authors of the research failed to provide the raw data that formed the basis of the research to the New England Journal of Medicine and The Lancet, the two organisations decided to withdraw the entire research, including its key claim that hydroxychloroquine is fatal for Covid-19 patients, on Thursday.
The study conducted in the U.S. and Canada was also the first to test whether the drug could prevent illness in people who have been exposed to the coronavirus.
Ever since Mr Trump’s pronouncement, there have been a lot of debates raised on if the widely available malaria drug would be effective in the fight against the COVID-19.
The debate on the efficacy of the drug also took place in Nigeria when a politician and founder of DAAR Communications, Raymond Dokpesi, said he used chloroquine as part of his treatment for COVID -19.
Proponents of the drug as a COVID-19 treatment argue it may need to be administered at an earlier stage in the disease to be effective. Others had suggested that it needs to be used in combination with the mineral zinc, which can help boost the immune system
In the study, the patients were picked at random to receive either an experimental treatment or a placebo considered the most reliable way to measure the safety and effectiveness of a drug.
The participants were healthcare workers and people who had been exposed at home to ill spouses, partners or parents.
The lead author of the study, David R. Boulware, from the University of Minnesota, told The New York Times that the take-home message for the general public is that ”if you’re exposed to someone with COVID-19, hydroxychloroquine is not an effective post-exposure preventive therapy.”
The study found 11.8 per cent of subjects given hydroxychloroquine developed symptoms compatible with COVID-19, compared with 14.3 per cent who got a placebo.
The difference was not statistically significant, meaning the drug was no better than the placebo.
More than 20 per cent of the trial subjects also took zinc, which had no significant effect.
The U.S. Food and Drug Administration cautioned in late April against the use of hydroxychloroquine in patients with heart disease due to an increased risk of dangerous cardiac rhythm problems.
Boulware said his trial had fewer participants than initially planned because of difficulty enrolling new subjects after the FDA’s warning.
“Our data is pretty clear that for post-exposure, this does not really work,” he said.
“I think both sides – one side who is saying ‘this is a dangerous drug’ and the other side that says ‘this works’ – neither is correct,” said Boulware.
Several trials of the drug have been stopped over concerns about its safety.
However, the World Health Organisation has also resumed its trial of hydroxychloroquine after the research was temporarily halted over safety concerns.
On May 25, WHO announced it had temporarily suspended its trial of the drug over safety concerns.
The announcement came days after a study published in the medical journal, The Lancet found that hospitalised COVID-19 patients treated with hydroxychloroquine had a higher risk of death than those who didn’t take it. That study is now being reexamined.
The Data Safety Monitoring Board decided there was no reason to discontinue the international trial after reviewing available data on the drug, WHO Director-General, Tedros Ghebreyesus, said during a press conference Wednesday at the agency’s Geneva headquarters.
Meanwhile, some European governments have banned hydroxychloroquine for COVID-19 patients, and U.S. hospitals have significantly cut back on its use.
Mr Ghebreyesus said the executive group received the new recommendation and endorsed the continuation of all arms of solidarity trial including hydroxychloroquine.
He said there’s no evidence that any drug actually reduces the mortality in patients who have COVID-19.
Mr Ghebreyesus also said the safety board will continue to closely monitor the safety of all therapeutics being tested in its trials, which involve more than 3,500 patients across 35 countries.