The antiviral drug remedesivir is effective in treating adults hospitalized with COVID-19 and evidence of lower respiratory tract infection, final trial data confirms.

In a study published Thursday in the New England Journal of Medicine, intravenous remdesivir shortened recovery time by five days and reduced mortality in some patients when compared to placebo, according to researchers with the National Institute of Allergy and Infectious Diseases. No other antiviral has been confirmed effective against the disease in a clinical trial, they reported.

Among more than 1,000 study participants, remdesivir recipients were given a 200 mg dose on day one, followed by 100 mg daily for up to nine days. By day 15, patients who received remdesivir were more likely than a placebo cohort to show clinical improvement. Mortality was also lower in the remdesivir group than in the placebo group at 15 and 29 days.

“Our data also suggest that treatment with remdesivir may have prevented the progression to more severe respiratory disease,” the researchers wrote.

Remdesivir, made by Gilead Sciences Inc, has been the subject of a number of studies since the first weeks of the pandemic. Promising early data prompted the Food and Drug Administration in May to issue an emergency use authorization (modified in August). This EUA permitted clinicians to use remdesivir in adults and children hospitalized with suspected or laboratory-confirmed COVID-19. Since that time, the drug has also received full or conditional approval in several other countries.  

Considering the high mortality in COVID-19, it is clear that antiviral treatment alone is not enough to aid all patients, the researchers concluded. Other studies are underway to evaluate remdesivir in combination with antibodies that neutralize SARS-CoV-2, the virus that causes COVID-19. This includes a study by the National Institutes of Health that began Thursday.