In this study, data from almost 15 000 hospitalised Covid-19 patients who were given hydroxychloroquine or chloroquine, and a control group of about 81 000 patients who didn't take the drug, were analysed.
More than 11,000 patients in England, Scotland, Wales and Northern Ireland were randomly assigned to get either standard of care or that plus one of these treatments: hydroxychloroquine, the HIV combo drug lopinavir-ritonavir, the antibiotic azithromycin, the steroid dexamethasone, the anti-inflammatory drug tocilizumab, or plasma from people who have recovered from Covid-19 that contains antibodies to fight the virus.
"We have, therefore, made a decision to stop enrolling participants to the hydroxychloroquine arm of the RECOVERY trial with immediate effect".
When the researchers tested blood cells from patients with severe COVID-19, who were not in the study, and compared it with samples from healthy volunteers, they found that the patients with severe COVID-19 had higher activity of the BTK protein and greater production of IL-6.
The announcement comes in the same week that the World Health Organisation (WHO) restarted its trials of hydroxychloroquine after they were temporarily halted because of a now-retracted study in The Lancet medical journal.
Lancet's "expression of concern", which is a means to alert readers about the integrity of a paper, followed several scientific questions being raised about the data for 96,000 patients that was reported in the paper by its author Mandeep Mehra.
Three authors on the Lancet paper requested the retraction, after initiating an independent review of the raw hospital patient data summarized and provided by Surgisphere, a small Chicago-based company operated by Sapan Desai, the fourth author of the study.
They said about half of the patients, did not receive HCQ at any time during their hospitalisation.
Article on Alleged Danger of Hydroxychloroquine Shown To Be 'Fake News'
"Each of these drug regimens was associated with decreased in-hospital survival and an increased frequency of ventricular arrhythmias when used for treatment of COVID-19".
An influential article that found hydroxychloroquine increases the risk of death in coronavirus patients has been retracted over data concerns. "As a result, they have concluded that they 'can no longer vouch for the veracity of the primary data sources'".
The study prompted a media storm, particularly after President Donald Trump revealed at a press conference he was taking the drug prophylactically to ward off the coronavirus.
He added that the drug was "quite toxic" so halting the trials would be of benefit to patients.
"Although it is disappointing that this treatment has been shown to be ineffective, it does allow us to focus care and research on more promising drugs".
The WHO said on 3 June that it would resume its trials after halting them last month. The drugs have shown efficacy in some studies, including in India and the United States, and large clinical trials are underway examining their safety and effectiveness.
They also claimed to have examined 8,910 COVID-19 patients from mid-March at almost 170 medical facilities in Asia, Europe and North America.
"The executive group received this recommendation and endorsed the continuation of all arms of solidarity trial, including hydroxychloroquine".
World Health Organization resumes trial of hydroxychloroquine drug
A much-anticipated study, co-authored by Canadian researchers, has found that hydroxychloroquine - a drug much-touted by U.S. The New England Journal of Medicine published a new study that shows hydroxychloroquine's inefficacy in treating COVID-19.