Pfizer announced that the new crown oral antiviral drug has been authorized by the US FDA for emergency use

Image source: Screenshot of the official website

On December 22, 2021, New York time, Pfizer announced that paxlovid, a new coronavirus oral antiviral drug developed by its company, has been urgently authorized to use (EUA) by the US Food and Drug Administration (FDA) for the treatment of adults and children with mild to moderate covid-19 (over 12 years old, weighing at least 40 kg).

About Paxlovid

Paxlovid is a compound consisting of Nirmatrelvir (PF-07321332) tablets and ritonavir tablets, which blocks viral replication by blocking SARS-CoV-2-3CL protease activity. However, the metabolic activity of CYP3A4 by the liver drug enzyme will be reduced, and ritonavir is an antiretroviral drug that can effectively inhibit the activity of the liver drug enzyme CYP3A4, so the combination of the two makes paxlovid the drug effect to the maximum. Currently, the FDA approves the use and dosage of the drug as follows: Nirmatrelvir 2 tablets (total 300 mg) and ritonavir 1 tablet (100 mg) for a combination of twice daily for a total of five days.

Data sources

The U.S. FDA authorized the drug for emergency use based on data from the Phase II/III EPIC-HR (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients) trial, which enrolled non-hospitalized adults aged 18 years and older with a high risk of developing severe illness diagnosed with COVID-19. The results showed that adults treated with Paxlovid had an 89% lower risk of hospitalization or death from any cause associated with COVID-19 compared to placebo within 3 days of symptom onset (primary endpoint). By day 28, there were no deaths in the treatment group and 9 deaths in the placebo group. Similar outcomes (secondary endpoints) were also observed in patients treated within 5 days of symptom onset, with an 88% lower risk of COVID-19-related hospitalization or death from any cause, and no deaths were observed in the treatment group. Adverse events occurred to a similar extent in the treatment and placebo groups, most of which were mild.

Effective for the Omikejong variant?

Due to the high mutation rate of the SARS-CoV-2 virus, those worrisome variants (such as the Delta and Omikejong variants) are immune to treatments that inhibit the spike protein on the surface of the SARS-CoV-2 virus. However, Paxlovid inhibits viral replication within cells by binding to proteases of the SARS-CoV-2 virus. Nirmatrelvir has shown consistent in vitro antiviral activity against currently of interest virus variants. In addition, Nirmatrelvir has shown in vitro tests a strong inhibitory effect on the SARS-CoV2-3CL protease associated with the Omicron variant. This suggests that Nirmatrelvir has the potential to maintain strong antiviral activity against the Omiljung variant.

Note: Paxlovid has not been approved, but has been authorized by the FDA for "emergency use." Its current access is limited to: (1) Paxlovid is not authorized to treat critically ill COVID-19 patients who need to be hospitalized; (2) Paxlovid is not authorized for pre- or post-exposure prevention of COVID-19; and (3) Paxlovid is not authorized for continuous use for more than 5 consecutive days.

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