Tofacitinib, which is taken orally, was tested in a trial of 289 patients hospitalised with severe Covid across 15 locations in Brazil.

Half of them received the drug – a 10 mg pill twice a day – and standard care like glucocorticoids that tamp down an overactive immune response. The other half received a placebo and standard care.

After 28 days, 18.1% of the group receiving tofacitinib progressed to respiratory failure or death, compared with 29% in the placebo group. This represented a statistically significant relative risk reduction of 63%.

Respiratory failure refers to a patient requiring non-invasive ventilation through an oxygen mask, or being intubated and placed on a mechanical ventilator.

Deaths after 28 days occurred in 2.8% of patients in the tofacitinib group and in 5.5% of those in the placebo group.

Serious side effects occurred in 14.1% in the tofacitinib group and in 12% in the placebo group.

“We are encouraged by the initial findings of our randomised trial,” said Dr Otavio Berwanger of Hospital Israelita Albert Einstein, which coordinated the trial in collaboration with Pfizer.

“These results provide new information which indicates that the use of tofacitinib, when added to standard of care, may further reduce the risk of death or respiratory failure in this patient population.”

Tofacitinib is approved in the United States to treat conditions such as rheumatoid arthritis, psoriatic arthritis and ulcerative colitis.