Pfizer starts dosing patients in oral Covid-19 drug trial

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-hospitalised, symptomatic adult patients.

The company and its rivals, including US-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.

Pfizer's mid-to-late-stage trial in 1,140 participants would study the therapy, PF-07321332, in combination with a low dose of ritonavir, which has been used with other antivirals too, the company said.

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-hospitalised 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 authorisation in the fourth quarter.