Trials of hydroxychloroquine on coronavirus patients have been halted after they failed to reduce mortality.
The malaria drug and a combination HIV drug lopinavir/ritonavir was trialled on patients infected with Covid-19.
In a statement, the World Health Organisation said: “These interim trial results show that hydroxychloroquine and lopinavir/ritonavir produce little or no reduction in the mortality of hospitalised Covid-19 patients when compared to standard of care."
Referring to large multi-country trials that the agency is leading, the WHO added: "Solidarity trial investigators will interrupt the trials with immediate effect".
The UN agency said the decision, taken on the recommendation of the trial’s international steering committee, does not affect other studies where those drugs are used for non-hospitalised patients or as a prophylaxis.
Another branch of the WHO-led trial is looking at the potential effect of Gilead’s antiviral drug remdesivir on Covid-19.
The European Commission on Friday gave remdesivir conditional approval for use after being shown to shorten hospital recovery times.
The solidarity trial started out with five branches looking at possible treatment approaches to Covid-19: standard care; remdesivir; hydroxychloroquine; lopinavir/ritonavir; and lopanivir/ritonavir combined with interferon.
The setback comes as the WHO also reported over 200,000 new cases globally of the disease for the first time in a single day.
The United States accounted for 53,213 of the total 212,326 new cases recorded on Friday, the WHO said.
The previous highest daily figure for new cases was 189,077, which was recorded on June 28.
There have been more than 11 million confirmed cases worldwide so far, with an estimated 525,000 deaths.
According to the WHO, a further 5,134 deaths were recorded in the 24 hours to 10am today.
In the US a further 53,213 new infections were recorded in the past 24 hours.
This was closely followed by Brazil, with 48,105.
India had a further 22,771 people testing positive for the deadly virus.
The UK has confirmed 519 new cases in that time.
It comes as countries which were heavily hit in the early days of the outbreak begin to ease their lockdown restrictions.
Spanish authorities today put 200,000 residents back in lockdown following a surge of cases in Catalonia.
Residents of El Segria, including the ancient city of Lleida, have been confined and roadblocks set up since midday on Saturday due to a worrying surge in cases that comes amid fears of a second wave of Covid-19.
The global figures should be taken with a pinch of salt, however, as different countries have different testing capabilities.
The latest WHO report said: "Caution must be taken when interpreting all data presented.
"Differences are to be expected between information products published by WHO, national public health authorities, and other sources using different inclusion criteria and different data cut-off times."