With authorisation, Pfizer’s oral antiviral candidate Paxlovid is an investigational SARS-CoV-2 protease inhibitor that could be prescribed at the first sign of COVID-19 infection.

Pfizer has announced an agreement with the UK government to supply an additional 2.5 million treatment courses of its investigational candidate Paxlovid (nirmatrelvir), subject to local authorisation. This is in addition to the 250,000 treatment courses previously contracted by the UK government, bringing the total amount of treatment courses to 2.75 million.

Paxlovid is an investigational SARS-CoV-2 protease inhibitor antiviral therapy, developed to be administered orally. If authorised, it can be prescribed at the first sign of COVID-19 infection or, pending clinical success and subject to regulatory approval, could help patients avoid severe illness which can lead to hospitalisation or death.

Nirmatrelvir is designed to block the activity of the SARS-CoV-2 3CL protease, an enzyme that the coronavirus needs to replicate. Co-administration, with a low dose of ritonavir, helps slow the metabolism – or breakdown – of nirmatrelvir, allowing it to remain active in the body for longer periods of time at higher concentrations to help tackle the virus.

If authorised, Paxlovid will be administered at a dose of 300mg (two 150mg tablets) of nirmatrelvir with one 100mg tablet of ritonavir, given twice daily for five days.

Albert Bourla, chairman and CEO of Pfizer, commented: “Final data from our phase 2/3 trial in high-risk participants confirmed the overwhelming efficacy of Paxlovid in reducing the risk of hospitalisation by nearly 90%, compared to placebo when treated within both three and five days of symptom onset and no deaths. We are pleased that the UK government recognises the importance of this potential treatment option.

“As we continue to combat the virus, we are in discussions with governments around the world to help ensure we get this potential treatment to patients as quickly as possible, subject to authorisation or approval.”