Pfizer launches early study of COVID-19 antiviral therapeutic

Pfizer has announced that it is advancing its investigational oral antiviral candidate for COVID-19 into the next stage of a phase 1 clinical trial. 

Pfizer is progressing to multiple ascending doses of the candidate, PF-07321332, after completing the dosing of single ascending doses in a phase 1 trial of the antiviral therapy.

PF-07321332 is a SARS-CoV-2-3CL protease inhibitor that is designed to bind to a protease (also known as a viral enzyme) to prevent the virus from replicating in the cell.

Previously, protease inhibitors have been effective for the treatment of other viral pathogens, including HIV and hepatitis C virus, when administered alone and in combination with additional antivirals.

Pfizer’s COVID-19 protease inhibitor has demonstrated ‘potent’ in vitro anti-viral activity against SARS-CoV-2, the virus which causes COVID-19, as well as activity against other coronaviruses.

This in vitro data suggests the potential benefit of the treatment in COVID-19 as well as its potential use to address future coronavirus threats, Pfizer said in a statement.

In addition to PF-07321332, Pfizer is also investigating an intravenously administered protease inhibitor, PF-07304814, that is currently in a phase 1b multi-dose trial in hospitalised COVID-19 patients.

“We have designed PF-07321332 as a potential oral therapy that could be prescribed at the first sign of infection, without requiring patients to be hospitalised or in critical care,” said Mikael Dolsten, chief scientific officer and president, worldwide research, development and medical of Pfizer.

“At the same time, Pfizer’s intravenous antiviral candidate is a potential novel treatment option for hospitalised patients. Together, the two have the potential to create an end-to-end treatment paradigm that complements vaccination in cases where disease still occurs,” he added.

Pfizer has already found success in its response to the COVID-19 pandemic, with its BioNTech-partnered vaccine becoming the first to receive an emergency authorisation last year.

With its antiviral candidates, Pfizer is now aiming to enter the COVID-19 therapeutic space, where Regeneron and Eli Lilly have largely dominated so far.

Regeneron’s antibody cocktail (casirivimab and imdevimab) has been granted an emergency use authorisation (EUA) by the US Food and Drug Administration (FDA) for the treatment of certain mild-to-moderate COVID-19 patients.

Lilly’s monoclonal antibody (mAb) bamlanivimab has been given an EUA for the treatment of mild-to-moderate COVID-19 in adults and paediatric patients.

A combination of bamlanivimab and another mAb, etesevimab, has also been approved for emergency use in the US.