New study shows antiviral remdesivir prevents disease progression in monkeys with COVID-19

Early treatment with the experimental antiviral drug remdesivir significantly reduced clinical disease and damage to the lungs of rhesus macaques infected with SARS-CoV-2, the virus that causes COVID-19, according to a release of the US National Institutes of Health on Friday.

The study, conducted by NIH scientists, was designed to follow dosing and treatment procedures used for hospitalized COVID-19 patients being administered remdesivir in a large, multi-center, clinical trial led by NIH's National Institute of Allergy and Infectious Diseases.

The study involved two groups of six rhesus macaques. One group of monkeys received remdesivir and the other animals served as an untreated comparison group.

Scientists infected both groups with SARS-CoV-2. Twelve hours later the treatment group received a dose of remdesivir intravenously, and then received a daily intravenous booster dose thereafter for the next six days.

The scientists timed the initial treatment to occur shortly before the virus reached its highest level in the animals' lungs.

Twelve hours after the initial treatment, the scientists examined all animals and found the six treated animals in significantly better health than the untreated group, a trend that continued during the seven-day study.

They reported that one of the six treated animals showed mild breathing difficulty, whereas all six of the untreated animals showed rapid and difficult breathing.

The amount of virus found in the lungs was significantly lower in the treatment group compared to the untreated group, and SARS-CoV-2 caused less damage to the lungs in treated animals than in untreated animals, according to the study.

The scientists noted that the data supports initiating remdesivir treatment in COVID-19 patients as early as possible to achieve maximum treatment effect.

They also noted that while remdesivir helped prevent pneumonia, it did not reduce virus shedding by the animals.

"This finding is of great significance for patient management, where a clinical improvement should not be interpreted as a lack of infectiousness," said the study.

The study has been posted on the preprint server bioRxiv. The findings are not yet peer-reviewed and should not be considered clinical advice, but are being shared to assist the public health response to COVID-19, said the NIH.