Pfizer has commenced a Phase 2/3 study of its oral Covid-19 treatment Paxlovid (nirmatrelvir and ritonavir) in non-hospitalised, symptomatic, paediatric patients who are at high risk of progression.

The Phase 2/3 study, dubbed Evaluation of Protease Inhibition for Covid-19 in Paediatric Patients (EPIC-PEDS), will evaluate the safety, pharmacokinetics, and efficacy of Paxlovid.

It is an open-label, multi-centre, single-arm study, designed to enrol 140 paediatric participants, aged below 18 years of age, into two cohorts.

Participants aged six to 17 years, weighing at least 40kg will be included in Cohort 1, while those aged six to 17 years, weighing between 20kg and 40kg will be added to Cohort 2.

The participants in Cohort 1 would receive Paxlovid (nirmatrelvir 300mg/ritonavir100mg) as a twice-daily treatment for five days, which is currently the authorised dosing in this population.

The Cohort 2 participants would receive Paxlovid (nirmatrelvir150mg/ritonavir100 mg) as an oral twice-daily therapy for five days.

Pfizer worldwide research, development and medical president and chief scientific officer Mikael Dolsten said: “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 hospitalisation or death.

“Paxlovid is already authorised or approved in many countries around the world, with more than 1.5 million treatment courses delivered thus far and 30 million expected by July to help combat this devastating disease.

“We are proud to expand studies of our novel Covid-19 treatment to include paediatric participants to further evaluate the safety and efficacy of this treatment in this important population.”

Paxlovid is currently authorised in the US, for emergency use in high-risk adult and paediatric patients, aged 12 years and above, weighing at least 40kg.

In November last year, Pfizer has announced that its investigational oral antiviral candidate has significantly reduced the Covid-19 related complications, in the Phase 2/3 EPIC-HR trial.

In the study, Paxlovid reduced the risk of Covid-19-related hospitalisation or death compared to placebo, by 89% within three days, and 88% within five days from symptom onset.

Pfizer said that it is developing a suitable formulation for three additional cohorts for age-groups, younger than six years old and will include the younger age groups in the trial.

In the EPIC-PEDS trial, an independent Data Monitoring Committee (DMC) will review safety data of participants in each cohort.

The study data will be further used for determining the dose range in this population, along with expanding the indication to younger age groups and lower weights, said Pfizer.