Mixed Results for Paxlovid in Standard Risk Patients With COVID-19

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The study evaluated Paxlovid in both vaccinated and unvaccinated patients with COVID-19 at standard risk for progressing to severe disease.

Additional findings were announced from a phase 2/3 study evaluating the efficacy and safety of Paxlovid™ (nirmatrelvir tablets co-packaged with ritonavir tablets) in patients with COVID-19 who are at standard risk of progressing to severe disease.

Paxlovid is currently authorized for emergency use by the Food and Drug Administration (FDA) for the treatment of mild to moderate COVID-19 patients who are at high risk for progression to severe disease, including hospitalization or death. The authorization was based on data from the EPIC-HR study (ClinicalTrials.gov Identifier: NCT04960202), which included patients with COVID-19 who had at least 1 characteristic or underlying medical condition association with an increased risk of developing severe illness.

The randomized, double-blind, 2 arm, EPIC-SR study (ClinicalTrials.gov Identifier: NCT05011513) enrolled standard risk individuals who had a confirmed diagnosis of SARS-CoV-2 infection within 5 days prior to randomization; onset of symptoms within 5 days of randomization; and at least 1 characteristic or underlying medical condition associated with an increased risk of developing severe illness and were fully vaccinated against COVID-19 or, no characteristics associated with an increased risk of severe COVID-19 and were unvaccinated. Patients were randomly assigned 1:1 to receive either Paxlovid or placebo orally twice daily for 5 days. 

A previously reported interim analysis of 854 patients showed that treatment with Paxlovid did not meet the primary endpoint of self-reported, sustained alleviation of all symptoms for 4 consecutive days. A nonsignificant 70% relative risk reduction was observed in the key secondary endpoint of hospitalization or death.

In an updated analysis of 1153 patients enrolled through December 2021, treatment with Paxlovid showed a nonsignificant 51% relative risk reduction in hospitalization or death. Among 721 vaccinated adults with at least 1 risk factor, treatment with Paxlovid showed a nonsignificant 57% relative risk reduction.

Paxlovid treatment was associated with a 62% decrease in COVID-19-related medical visits per day compared with placebo (P =.0228). Medical visits included trips to the emergency room, urgent care, hospital admissions, and telehealth calls, among others. Compared with the placebo arm, there was a 72% reduction in the average number of days spent in the hospital among Paxlovid-treated patients.

While not statistically significant, there were no deaths or admissions to the intensive care unit in the Paxlovid arm compared with 1 death and 3 admissions to the intensive care unit in the placebo arm.

As for safety, treatment-emergent adverse events were comparable and mild in intensity between Paxlovid (23.1%) and placebo (23.4%), with comparable rates of serious adverse events (1.4% vs 1.9%, respectively) and discontinuation of study drug due to adverse events (1.7% vs 1%).

“Results from our phase 2/3 EPIC-HR and EPIC-SR studies, as well as post authorization experience, support the efficacy and safety profile for Paxlovid in the treatment of mild to moderate COVID-19 patients with at least 1 risk factor for progressing to severe COVID-19, regardless of vaccination status,” said Albert Bourla, Chairman and CEO, Pfizer.

Data from EPIC-SR will be included in the New Drug Application submission for Paxlovid, though enrollment in the study has ended due to low rates of hospitalization and death in the standard risk patient population.


Pfizer reports additional data on Paxlovid™ supporting upcoming New Drug Application submission to US FDA. News release. Pfizer Inc. June 14, 2022. Accessed June 15, 2022. https://www.businesswire.com/news/home/20220613005755/en/Pfizer-Reports-Additional-Data-on-PAXLOVID%E2%84%A2-Supporting-Upcoming-New-Drug-Application-Submission-to-U.S.-FDA