Pfizer Inc said on Wednesday it had started dosing in a mid-to-late-stage trial of its oral antiviral therapy for COVID-19 in non-hospitalized, symptomatic adult patients.
The company and its rivals, including U.S.-based Merck & Co Inc and Swiss pharmaceutical Roche Holding AG, have been racing to develop the first antiviral pill to be taken on early signs of the illness.
PF-07321332 is designed to block the activity of a key enzyme that is needed for the coronavirus to replicate.
To date, Gilead Sciences Inc's remdesivir, administered intravenously, is the only approved antiviral treatment for COVID-19 in the United States.
Merck and partner Ridgeback Biotherapeutics' molnupiravir is already being studied in a late-stage trial in non-hospitalized patients to see if it reduces the risk of hospitalization or death.
The companies said on Wednesday they had started a late-stage trial of molnupiravir for the prevention of COVID-19 infection.
Pfizer said in July if the PF-07321332 trial was successful, it would file for a potential emergency use authorization in the fourth quarter.