5 January 2022 - - The US government has committed to purchasing an additional 10m treatment courses of US-based pharmaceutical company Pfizer Inc's (NYSE: PFE) COVID-19 oral therapy, Paxlovid (nirmatrelvir [PF-07321332] tablets and ritonavir tablets), the company said.

This commitment will supplement the 10m treatment courses previously contracted by the US government, bringing the total amount of treatment courses to 20m.

Collectively, approximately 10m Paxlovid treatment courses have been accelerated for delivery by the end of June, with the remaining 10m to follow by the end of September.

Paxlovid includes nirmatrelvir, a novel main protease inhibitor originating in Pfizer's laboratories, which was specifically designed to block the activity of the SARS-CoV-2 Mpro, an enzyme that the coronavirus needs to replicate.

The US Food and Drug Administration recently authorized the emergency use of Paxlovid for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg [88 lbs]) with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.

Paxlovid is also currently authorized for conditional or emergency use in several countries across the globe.

Pfizer has submitted applications for regulatory approval or authorization to multiple regulatory agencies and anticipates further regulatory decisions to follow.

Pfizer said it is committed to working toward equitable access to Paxlovid for all people, aiming to deliver safe and effective antiviral therapeutics as soon as possible and at an affordable price.

During the pandemic, Pfizer will offer its oral therapy through a tiered pricing approach, pending country authorization or approval, based on the income level of each country to promote equity of access across the globe.

High and upper-middle income countries will pay more than lower income countries.

Pfizer continues to invest to support the manufacturing and distribution of Paxlovid, including exploring potential contract manufacturing options.

As a result of these efforts, Pfizer is raising its production projections from 80m to 120m courses of treatment by the end of 2022.

The company has entered into agreements with multiple countries and has initiated bilateral outreach to approximately 100 countries around the world.

Additionally, Pfizer has signed a voluntary license agreement with the Medicines Patent Pool for its oral treatment to help expand access, pending country regulatory authorization or approval, in 95 low- and middle-income countries that account for approximately 53% of the world's population.

Paxlovid is a SARS-CoV-2 main protease inhibitor (also known as SARS-CoV2 3CL protease inhibitor) therapy.

It was developed to be administered orally so that it can be prescribed at the first sign of infection or, pending clinical success of the rest of the EPIC development program and subject to regulatory authorization, at first awareness of an exposure potentially helping patients avoid severe illness (which can lead to hospitalization and death) or avoid disease development following contact with a household member who contracts COVID-19.

Nirmatrelvir [PF-07321332], which originated in Pfizer laboratories, is designed to block the activity of the Mpro, an enzyme that the coronavirus needs to replicate.

Co-administration with a low dose of ritonavir helps slow the metabolism, or breakdown, of nirmatrelvir in order for it to remain active in the body for longer periods of time at higher concentrations to help combat the virus.

Nirmatrelvir is designed to inhibit viral replication at a stage known as proteolysis, which occurs before viral RNA replication.

In preclinical studies, nirmatrelvir did not demonstrate evidence of mutagenic DNA interactions.

Current variants of concern can be resistant to treatments that inhibit the spike protein found on the surface of the SARS-CoV-2 virus, due to its high mutation rate.

Paxlovid, however, works intracellularly by binding to the protease of the SARS-CoV-2 virus to inhibit viral replication.

Nirmatrelvir has shown consistent in vitro antiviral activity against current variants of concern (i.e., alpha, beta, delta, gamma, lambda, and mu).

In addition, nirmatrelvir potently inhibited the Mpro associated with Omicron in an in vitro biochemical assay.

This indicates nirmatrelvir's potential to maintain robust antiviral activity against Omicron. Additional in vitro antiviral studies with this variant are underway.

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

One carton contains five blister packs of Paxlovid, as co-packaged nirmatrelvir tablets with ritonavir tablets, providing all required doses for a full five-day treatment course.

Paxlovid has not been approved, but has been authorized for emergency use by FDA under an EUA, for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct SARS CoV-2 viral testing, and who are at high-risk for progression to severe COVID-19, including hospitalization or death.

The emergency use of Paxlovid is only authorized for the duration of the declaration that circumstances exist justifying the authorization of the emergency use of drugs and biological products during the COVID-19 pandemic under Section 564(b) (1) of the Act, 21 USC. § 360bbb-3(b) (1), unless the declaration is terminated or authorization revoked sooner.