Pfizer has initiated a phase 2/3 study evaluating Paxlovid (nirmatrelvir with ritonavir) in nonhospitalized, symptomatic, pediatric patients with COVID-19 who are at risk of progression to severe disease.

Paxlovid consists of nirmatrelvir and low-dose ritonavir. Nirmatrelvir inhibits the viral replication of SARS-CoV-2 by blocking the activity of the SARS-CoV-2-3CL protease. Coadministration with low-dose ritonavir slows the metabolism of nirmatrelvir and prolongs its activity. 

The open-label, multicenter, single-arm EPIC-PEDS study ( Identifier: NCT05261139) will include approximately 140 patients less than 18 years of age with a confirmed diagnosis of COVID-19. Patients are required to have an initial onset of COVID-19 signs/symptoms within 5 days prior to enrollment, with at least 1 of the signs/symptoms present at enrollment, and at least 1 medical condition associated with an increased risk of progression to severe disease.

Cohort 1 of the study will include patients aged 6 to 17 years weighing at least 40kg (88lbs); this group will receive Paxlovid 300mg/100mg orally twice daily for 5 days. Cohort 2 will include patients aged 6 to 17 years weighing more than 20kg (44lbs) and less than 40kg (88lbs); this group will receive Paxlovid 150mg/100mg orally twice daily for 5 days.

The Company is also looking to enroll patients younger than 6 years of age in the trial and is working to develop an age-appropriate formulation for this population. 

“There is a significant unmet need for outpatient treatments that can be taken by children and adolescents to help prevent progression to severe illness, including hospitalization or death,” said Mikael Dolsten, CSO and President, Worldwide Research, Development and Medical, Pfizer. “We are proud to expand studies of our novel COVID-19 treatment to include pediatric participants to further evaluate the safety and efficacy of this treatment in this important population.”

Paxlovid is currently authorized under emergency use for the treatment of mild to moderate COVID-19 in patients 12 years of age and older weighing at least 40kg with positive results of direct SARS-CoV-2 testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.

The authorization was based on data from the phase 2/3 EPIC-HR study ( Identifier: NCT04960202), which compared the efficacy and safety of Paxlovid to placebo in patients with laboratory-confirmed diagnosis of SARS-CoV-2 infection within a 5-day period with mild to moderate symptoms. Final trial results showed that Paxlovid significantly reduced the risk of COVID-19-related hospitalization or death from any cause within 3 and 5 days of symptom onset.


Pfizer initiates phase 2/3 study of novel COVID-19 oral treatment in pediatric participants. News release. Pfizer Inc. Accessed March 9, 2022.