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Merck’s new COVID-19 pill: ‘Game changer’ or just one more tool?


On Merck’s heels: Pfizer, Roche, Atea

Pfizer is studying an antiviral pill, PF-07321332, a protease inhibitor that blocks the protease enzymes and halts replication of the virus.

In addition to studying the drug in infected patients at high risk of severe illness and in those at typical risk, Pfizer launched a phase 2-3 study in late September that will enroll people who live in the same household as a person with a confirmed, symptomatic COVID-19 infection to see if the drug can prevent disease in those who have been exposed.

Atea and Roche’s COVID pill, AT527, is in phase 3 trials as well. AT527 is an inhibitor of polymerase, an enzyme many viruses have, to stop replications. Atea is evaluating the drug to reduce disease “burden” and for both pre- and postexposure prevention.

Big picture: Role of COVID-19 pills

It may be necessary to target the coronavirus with more than one antiviral agent, said Dr. Fichtenbaum, a principal investigator for the AT527 trials.

“Sometimes viruses require two or three active agents to control their replication,” he said, citing information gleaned from other viral research, such as HIV. For control of HIV infection, a cocktail or combination of antivirals is often recommended.

That may well be the case for COVID-19, Dr. Fichtenbaum said. The goal would be to attack the virus at more than one pathway.

A version of this article first appeared on


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