French pharmaceutical company Sanofi announced Tuesday that it was halting clinical trials of its drug Kevzara for use against the novel coronavirus.

Recent international clinical trials conducted with the drug — typically used for rheumatoid arthritis — have produced adverse reactions in some patients, including pneumonia and even death.

Sanofi is one of several companies currently attempting to develop a vaccine against COVID-19. It manufactures Kevzara with its American partner Regeneron.

John Reed, Sanofi’s global head of research and development, expressed appreciation for his team’s efforts in testing the drug.

“Although this trial did not yield the results we hoped for, we are proud of the work that was achieved by the team to further our understanding of the potential use of Kevzara for the treatment of COVID-19,” he said in a statement to Radio France International.

Exactly one month ago, the European Commission promised to buy 300 million doses of a potential vaccine developed by Sanofi. As part of that pledge, all 27 EU member countries could also have separately purchased amounts of the vaccine.

On the same day, the US also promised $2.1 billion to Sanofi and British pharmaceutical GlaxoSmithKline (GSK) for the development of a vaccine.

Previously, Russia announced in August that its scientists had developed a vaccine that successfully combated the virus. Although approved by Russian health authorities, the drug had not been put through phase III clinical trials necessary to prove the efficacy and safety of its use.

The coronavirus pandemic has claimed more than 851,000 lives in 188 countries and regions since originating in China last December. The US, Brazil, India, and Russia are currently the worst-hit countries.

Over 25.5 million COVID-19 cases have been reported worldwide, with recoveries exceeding 16.8 million, according to figures compiled by the US-based Johns Hopkins University.

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