On Dec. 22, 2021, Pfizer announced that the U.S. Food and Drug Administration (FDA) had authorized the emergency use of PAXLOVID (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg [88 lbs]) with positive results of direct SARS-CoV-2 viral testing, and who were at high risk for progression to severe COVID-19, including hospitalization or death.

The treatment includes nirmatrelvir, a novel main protease (Mpro) inhibitor originating in Pfizerﾒs laboratories, which was specifically designed to block the activity of the SARS-CoV-2 Mpro, an enzyme that the coronavirus needs to replicate.