According to the company, Paxlovid would be the first 3CL protease inhibitor to be used as an oral antiviral against SARS-CoV-2, if authorised


Pfizer World Headquarters in Manhattan, New York, New York. (Credit: Coolcaesar/Wikipedia.)

Pfizer has filed an application with the US Food and Drug Administration (FDA) seeking emergency use authorisation (EUA) of its investigational oral antiviral Paxlovid (PF-07321332, ritonavir).

The submission indicates the drug for the treatment of mild to moderate Covid-19 in patients, who are at elevated risk of hospitalisations or death.

Paxlovid is an investigational oral antiviral that specifically targets the activity of SARS-CoV-2-3CL protease, an enzyme that the coronavirus needs to replicate.

The drug was designed for oral administration, allowing it to be prescribed at the first sign of infection or exposure, to help patients prevent severe illness, said the company.

According to the US drugmaker, Paxlovid would be the first 3CL protease inhibitor to be used as an oral antiviral against SARS-CoV-2, if authorised or approved.

It will be administered at a 300mg dose, in the form of two 150mg tablets, with one 100mg tablet of ritonavir, given twice daily for five days.

Pfizer chairman and CEO Albert Bourla said: “With more than five million deaths and countless lives impacted by this devastating disease globally, there is an urgent need for life-saving treatment options.

“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 authorised, underscores the critical role that oral antiviral therapies could play in the battle against Covid-19.

“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.”

Pfizer’s regulatory filing is based on positive clinical data from the interim analysis of Phase 2/3 EPIC-HR study in adults with confirmed Covid-19, who are at risk of severe disease.

In the study, treatment using Paxlovid showed an 89% reduction in risk of Covid-19-related hospitalisation or death compared to placebo, within three days of symptom onset.

The treatment group showed similar results within five days of symptom onset, with comparable treatment-emergent adverse events, and no deaths reported.

The US regulatory agency has initiated a rolling submission of non-clinical data for Paxlovid last month; started rolling submissions in the UK, Australia, New Zealand and South Korea.

In a separate development, Pfizer has signed an agreement with the Medicines Patent Pool (MPP), a United Nations-backed public health organisation, to licence its oral Covid-19 antiviral candidate PF-07321332.

PF-07321332 is administered in combination with low dose ritonavir.

Under the license agreement, Pfizer and MPP will provide qualified generic manufacturers with sub-licenses to supply PF-07321332 plus ritonavir to 95 low- and lower-middle-income countries.

Previously, Merck signed a similar licensing agreement with the MPP to enhance global access for its investigational Covid-19 antiviral medicine, molnupiravir.