The US National Institutes of Health (NIH) has initiated a multi-site clinical trial evaluating an investigational antiviral for the treatment of COVID-19, the agency has announced.

The therapeutic, known as S-217622 or ensitrelvir fumaric acid, was discovered by Hokkaido University of Japan; and Shionogi & Co., Ltd., a Japanese pharmaceutical company.

The trial is assessing whether S-217622 can improve clinical outcomes for patients who are hospitalised for the management of COVID-19 as compared to a placebo. It will enrol approximately 1,500 people at sites worldwide, Xinhua news agency reported.

S-217622 is the first agent to be evaluated in a new global, adaptive clinical research protocol known as Strategies and Treatments for Respiratory Infections & Viral Emergencies (STRIVE), according to the NIH.

"We hope results from this trial can be applied to improve the standard of care for people with COVID-19, which still causes hundreds of deaths each day in the United States, as well as to strengthen our pandemic preparedness," said H. Clifford Lane, deputy director for Clinical Research and Special Projects at the US National Institute of Allergy and Infectious Diseases.

"The STRIVE protocol and clinical research infrastructure can be adapted to evaluate additional agents for COVID-19, as well as therapeutics for other respiratory pathogens," he said.