The Merck logo is seen at a gate to the Merck & Co campus in Rahway, New Jersey, July 12, 2018. (Photo: Brendan McDermid/Reuters)

If it gets authorization, molnupiravir, which is designed to introduce errors into the genetic code of the virus, would be the first oral antiviral medication for COVID-19.

Merck and partner Ridgeback Biotherapeutics said they plan to seek US emergency use authorization for the pill as soon as possible and to make regulatory applications worldwide.

"An oral antiviral that can impact hospitalization risk to such a degree would be game-changing," said Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security.

Pfizer and Swiss drugmaker Roche Holding AG are also racing to develop an easy-to-administer antiviral pill for COVID-19.