Pfizer Seeks EUA for Paxlovid, a Novel Oral Antiviral for COVID-19

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The submission is supported by data from the phase 2/3 EPIC-HR study.

Pfizer is seeking Emergency Use Authorization (EUA) for its investigational COVID-19 oral antiviral candidate, Paxlovid (PF-07321332/ritonavir), for the treatment of mild to moderate COVID-19 in patients at increased risk of hospitalization or death.

Paxlovid is a SARS-CoV-2 protease inhibitor consisting of PF-07321332 and low-dose ritonavir. PF-07321332 inhibits the viral replication of SARS-CoV-2 by blocking the activity of the SARS-CoV-2-3CL protease. Co-administration with low-dose ritonavir slows the metabolism of PF-07321332 and prolongs its activity.

The submission is supported by data from the randomized, double-blind, 2-arm, phase 2/3 EPIC-HR study ( Identifier: NCT04960202), which compared the efficacy and safety of Paxlovid to placebo in 1219 patients with laboratory-confirmed diagnosis of SARS-CoV-2 infection within a 5-day period with mild to moderate symptoms. Patients were required to have at least 1 characteristic or underlying medical condition associated with an increased risk of developing severe illness from COVID-19. 

Interim analysis showed that patients in the Paxlovid treatment arm had a significantly greater reduction in the risk of COVID-19-related hospitalization or death from any cause within 3 days of symptom onset (primary endpoint) compared with placebo. There were similar findings reported in patients treated within 5 days of symptom onset. In the overall study population, there were no deaths reported in the Paxlovid arm and 10 deaths in the placebo arm.

“The overwhelming efficacy achieved in our recent clinical study of Paxlovid, and its potential to help save lives and keep people out of the hospital if authorized, underscores the critical role that oral antiviral therapies could play in the battle against COVID-19,” said Albert Bourla, Chairman and CEO, Pfizer. “We are moving as quickly as possible in our effort to get this potential treatment into the hands of patients, and we look forward to working with the US FDA on its review of our application, along with other regulatory agencies around the world.”

If authorized, Paxlovid will be administered as two 150mg tablets of PF-07321332 with one 100mg tablet of ritonavir, given twice daily for 5 days.


Pfizer seeks Emergency Use Authorization for novel COVID-19 oral antiviral candidate. News release. Pfizer Inc. Accessed November 16, 2021.