Pfizer has reported interim analysis data from Phase II/III clinical trial where its experimental oral antiviral candidate, Paxlovid (PF-07321332; ritonavir), substantially reduced Covid-19-associated mortality and hospitalisation.
Paxlovid is an experimental inhibitor of SARS-CoV-2-3CL protease, an enzyme required by the coronavirus for replication.
Named EPIC-HR, the double-blind, randomised trial is designed to enrol non-hospitalised adult subjects with Covid-19 and are at an increased risk of disease progression.
Subjects were categorised into a 1:1 ratio to receive oral doses of either Paxlovid or placebo every 12 hours for five days.
The initial analysis of the interim data set assessed results from 1,219 adult subjects who were enrolled by 29 September this year.
In the primary goal, subjects receiving the Paxlovid treatment within three days of symptom development had an 89% decline in Covid-19-associated hospitalisation or mortality risk from any cause versus placebo.
Furthermore, 0.8% of the subjects in the Paxlovid arm were admitted to the hospital by day 28 as against 7% in the placebo group who were hospitalised or died.
The company noted that the data was highly statistically significant.
A similar trend of reduction in hospitalisation or morality linked to the disease were reported in subjects receiving the antiviral treatment within five days of symptom development.
Only 1% of these Covid-19 patients treated with Paxlovid were admitted to the hospital by day 28 versus 6.7% who were given a placebo, indicating a greater statistical significance.
By day 28, no cases of death were observed in the Paxlovid arm versus ten in the placebo group.
According to the independent Data Monitoring Committee recommendation and the US Food and Drug Administration’s (FDA) advice, Pfizer will stop subject enrolment due to the greater efficiency.
The company also plans to present these results as part of an ongoing rolling submission to the US FDA to obtain Emergency Use Authorization (EUA).
Pfizer chairman and CEO Albert Bourla said: “These data suggest that our oral antiviral candidate if approved or authorised by regulatory authorities, has the potential to save patients’ lives, reduce the severity of Covid-19 infections, and eliminate up to nine out of ten hospitalisations.”
In a previous development, Pfizer and BioNTech obtained FDA EUA for the use of their Covid-19 vaccine in children aged five to 11 years.