The US Government has signed an agreement with Pfizer to procure ten million courses of the company’s Covid-19 oral antiviral candidate, Paxlovid (PF-07321332; ritonavir), for $5.29bn, on obtaining the US Food and Drug Administration (FDA) authorisation.

The experimental antiviral PF-07321332 hinders the SARS-CoV-2-3CL protease activity, an enzyme required by the virus for its replication.

It is given along with a low ritonavir dose to delay PF-07321332’s metabolism, or breakdown aiding it to be active in the body for a longer time at greater concentrations to fight the virus.

Pfizer sought Emergency Use Authorization (EUA) from the FDA for Paxlovid to treat Covid-19 patients with mild-to-moderate symptoms.

According to the deal, Pfizer intends to deliver the ten million courses of the pill to the US Government starting later this year and ending next year.

In addition to this deal, the company signed advance purchase agreements with various nations and has begun bilateral outreach to nearly 100 countries globally.

Pfizer chairman and CEO Albert Bourla said: “We were thrilled with the recent results of our Phase II/III interim analysis, which showed overwhelming efficacy of Paxlovid in reducing the risk of hospitalisation among high-risk patients treated within three days of symptom onset by almost 90% and with no deaths, and are pleased the US government recognises this potential.

“It is encouraging to see a growing understanding of the valuable role that oral investigational therapies may play in combatting Covid-19 and we look forward to continuing discussions with governments around the world to help ensure broad access for people everywhere.”

Interim analysis data from the company’s Phase II/III clinical trial showed that Paxlovid lowered Covid-19-linked mortality and hospitalisation.