The World Health Organization (WHO) has temporarily suspended a clinical trial of the malaria drug hydroxychloroquine in Covid-19 patients over safety concerns, according to the organisation’s director-general Dr Tedros Adhanom Ghebreyesus.

The move comes after data from an observational study published in The Lancet journal revealed a higher mortality rate in patients treated with hydroxycholoroquine when given alone or with a macrolide.

During the observational study, hydroxychloroquine and chloroquine were assessed for their effects on hospitalised Covid-19 patients.

Ghebreyesus said: “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.”

The Solidarity Trial was launched more than two months ago to assess the safety and efficacy of four drugs and drug combinations against Covid-19.

According to the WHO, more than 400 hospitals across 35 countries are actively enrolling patients for the study and approximately 3,500 participants have been recruited from 17 countries.

The Executive Group of the trial, representing ten of the participating countries, met on 23 May and decided to review a comprehensive analysis of all data available globally.

This review will involve evidence gathered to date as part of the Solidarity Trial, particularly randomised available data, in order to assess the potential benefits and harms from hydroxychloroquine.

WHO noted that, while the hydroxychloroquine arm has been temporarily halted, the other arms of the trial are continuing.

Ghebreyesus added: “This concern relates to the use of hydroxychloroquine and chloroquine in Covid-19. I wish to reiterate that these drugs are accepted as generally safe for use in patients with autoimmune diseases or malaria.”

Earlier this month, data from a large-scale clinical study conducted by Columbia University Irving Medical Center in the US showed that Covid-19 patients treated with hydroxychloroquine did not experience better performance than those who did not receive the drug.