Pfizer announced the submission of a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for approval of PAXLOVID (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) for patients who are at high risk for progression to severe illness from COVID-19.
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PAXLOVID is currently authorized for emergency use 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.
The submission provides the longer-term follow-up data necessary for acceptance and potential approval.
According to the U.S. Centers for Disease Control and Prevention (CDC), 50-60% of the U.S. population is estimated to have one or more risk factors for progressing to severe COVID-19 illness.
These risk factors include any of the following: being aged 65 and older, obesity, diabetes, hypertension, smoking, physical inactivity, chronic kidney or liver disease, and immunocompromised conditions such as cancer, among others.
The NDA submission is supported by non-clinical and clinical data for PAXLOVID. It includes results from the Phase 2/3 EPIC-HR study (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients), which found that, compared to placebo, treatment with PAXLOVID reduced the risk of hospitalization or death from any cause by 88% in non-hospitalized, high-risk adult patients treated within five days of symptom onset; results from the final Clinical Study Report showed an 86% reduction in relative risk.
The submission is also comprised of the most recent analyses from the Phase 2/3 EPIC-SR study (Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients), which included data from both vaccinated patients with, and unvaccinated patients without, risk factors for severe COVID-19.
While the novel primary endpoint of self-reported, sustained alleviation of all symptoms for four consecutive days was not met, the data were supportive of the efficacy and safety data observed in EPIC-HR for use in patients at increased risk of progression to severe COVID-19 illness.
PAXLOVID is currently approved or authorized for conditional or emergency use in more than 65 countries across the globe to treat COVID-19 patients who are at increased risk for progressing to severe illness.
As of the end of May 2022, Pfizer had shipped more than 12 million treatment courses of PAXLOVID to nearly 40 countries around the world.
PAXLOVID is a SARS-CoV-2 main protease (Mpro) inhibitor (also known as SARS-CoV-2 3CL protease inhibitor) therapy.
It was developed to be administered orally so that it can be prescribed early after infection, potentially helping patients avoid severe illness (which can lead to hospitalization and death).
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 work by binding to the spike protein found on the surface of the SARS-CoV-2 virus.
PAXLOVID, however, works intracellularly by binding to the highly conserved Mpro (3CL protease) of the SARS-CoV-2 virus to inhibit viral replication. Nirmatrelvir has shown consistent in vitro antiviral activity against the following variants: Alpha, Beta, Delta, Gamma, Lambda, Mu, and Omicron BA.1 and BA.2.
PAXLOVID is generally 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. ■