Pfizer begins study of oral drug for prevention of COVID-19

Pfizer said on Monday it has started a mid-to-late-stage study testing its investigational oral antiviral drug for the prevention of COVID-19 infection among those who have been exposed to the virus.

The company and its rivals, including U.S.-based Merck & Co and Swiss pharmaceutical Roche Holding AG, have been racing to develop the first antiviral pill for COVID-19.

Pfizer said it would study the drug, PF-07321332, in up to 2,660 healthy adult participants aged 18 and older who live in the same household as an individual with a confirmed symptomatic COVID-19 infection.

The trial would test PF-07321332 with a low dose of ritonavir, an older medication widely used in combination treatments for HIV infection.

Merck and partner Ridgeback Biotherapeutics said earlier this month they had begun enrolling patients in a late-stage trial of their experimental drug molnupiravir for prevention of COVID-19 infection.

Pfizer had also said earlier this month it started a mid-to-late-stage trial of PF-07321332 for the treatment of COVID-19 in non-hospitalized, symptomatic adult patients.