US drugmaker Merck & Co Inc said on Saturday the experimental antiviral drug molnupiravir it is developing with Ridgeback Bio showed a quicker reduction in infectious virus in its phase 2a study among participants with early COVID-19.

“The secondary objective findings in this study, of a quicker decrease in infectious virus among individuals with early COVID-19 treated with molnupiravir, are promising,” said William Fischer, Associate Professor of Medicine at the University of North Carolina School of Medicine, in a statement from the companies.

The antiviral is being currently tested in a Phase 2/3 trial that is set to be completed in May.

Merck decided to focus on therapeutics after its two COVID-19 vaccines failed to generate desired immune responses, prompting it to abandon the program in January.