Vaccine Info

PAXLOVID Oral Antiviral (PF-07321332)

Authored by
Staff
Last reviewed
January 25, 2022
Share

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) Description

Pfizer Inc. Paxlovid™ (nirmatrelvir (PF-07321332) and ritonavir) is an oral antiviral therapeutic targeting the SARS-CoV-2 betacoronavirus to prevent COVID-19. Paxlovid is a protease inhibitor with potent in vitro antiviral activity against SARS-CoV-2 and other coronaviruses. It is an analog of GC373, where the aldehyde covalent cysteine acceptor replaced a nitrile.

By inhibiting the main protease, Paxlovid inhibits viral replication at a stage known as proteolysis, which occurs before viral RNA replication. Protease inhibitors bind to a viral enzyme (protease), preventing the virus from replicating in the cell. Protease inhibitors have effectively treated other viral pathogens, such as HIV and hepatitis C virus. Nirmatrelvir, a novel main protease (Mpro) inhibitor originating in Pfizer's laboratories, is specifically designed to block the activity of the SARS-CoV-2 Mpro, an enzyme that the coronavirus needs to replicate.

Paxlovid is co-administration with a low dose of ritonavir, a strong cytochrome P450 (CYP) 3A inhibitor, to slow the metabolism or breakdown of Paxlovid and to remain active in the body for more extended periods at higher concentrations to help combat the virus. Paxlovid works intracellularly by binding to the highly conserved Mpro of the SARS-CoV-2 virus. In preclinical studies, PF-07321332 did not demonstrate evidence of mutagenic DNA interactions. However, Ritonavir-boosted nirmatrelvir (Paxlovid) has significant and complex drug-drug interaction potential, primarily due to the ritonavir component of the combination.

Paxlovid was found to reduce the risk of hospitalization or death by 89% compared to placebo in nonhospitalized high-risk adults with COVID-19 in a clinical study. In addition, about 1% of patients (6 out of 607) who took Paxlovid within five days of the start of symptoms were hospitalized within 28 days of starting treatment compared with 6.7% of patients (41/612) given a placebo; none of the patients in the Paxlovid group died compared with ten patients in the placebo group.

Paxlovid became the first orally administered coronavirus-specific investigational protease inhibitor authorized by prescription only by the U.S. FDA on December 22, 2021. Paxlovid treatment should be initiated within five days of disease symptom onset, says the U.S. NIH. On December 16, 2021, the European Medicines Agency (EMA) announced that the human medicines committee issued advice on using Paxlovid to treat COVID-19. In addition, the EMA confirmed on January 10, 2022; it started evaluating Pfizer Europe MA EEIG's application for conditional marketing authorization for Paxlovid.

On January 12, 2022, the U.S. Clinician Outreach and Communication Activity conducted a digital call to review: 'What Clinicians Need to Know About the New Oral Antiviral Medications for COVID-19.' In addition, the U.S. NIH published on December 30, 2021: COVID-19 Treatment Guidelines Panel's Statement on Potential Drug-Drug Interactions Between Ritonavir-Boosted Nirmatrelvir (Paxlovid) and Concomitant Medications.

Chemical Formula: C23H32F3N5O4; DrugBank Accession Number DB16691; CAS Number 2628280-40-8; PubChem CID 155903259; Molecular Weight: 499.5.

To learn more, please visit New York-based Pfizer Inc. at www.Pfizer.com. (NYSE: PFE). Under the EUA, fact sheets that provide essential information about using Paxlovid to treat COVID-19 as authorized must be made available to healthcare providerspatients, and caregivers. Please see Full EUA Prescribing Information available at www.fda.gov. and www.COVID19oralRx.com. 

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) Effectiveness Against Coronavirus Variants (Omicron)

Current coronavirus variants 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 of the SARS-CoV-2 virus. Pfizer Inc. shared results from multiple studies demonstrating on January 18, 2022, that the in vitro efficacy of nirmatrelvir, the active main protease (Mpro) inhibitor of PAXLOVID, is maintained against the SARS-CoV-2 variant Omicron. Pfizer also announced on December 14, 2021, recent in vitro data confirm that nirmatrelvir is a potent inhibitor of the Omicron 3CL protease, which, combined with existing in vitro antiviral and protease inhibition data from other Variants of Concern (VoC), including Delta, indicates that PAXLOVID will retain robust antiviral activity against current VoCs as well as other coronaviruses.

As of January 25, 2022, the U.S. NIH OpenData Portal is not reporting Paxlovid's in vitro Therapeutic Activity against SARS-CoV-2 coronavirus variants. On January 19, 2022, the NIH updated the COVID-19 Treatment Guidelines Panel released on December 23, 2021. This update addresses the fact that the B.1.1.529 (Omicron) variant of concern is now the dominant SARS-CoV-2 variant in all U.S. Department of Health and Human Services regions. The purpose of this statement is to provide clinicians with guidance on the use of Paxlovid for the treatment of nonhospitalized patients with COVID-19 who are at high risk of progressing to severe disease.

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) Availability

As of January 25, 2022, Paxlovid was authorized by Australia, the U.S., Bahrain, CanadaIsrael, South Korea, the United Kingdom, Ontario, and Mexico. Marketing authorization in Europe and India is pending.

For the U.S. market, the U.S. Department of Health and Human Services Office of the Assistant Secretary for Preparedness and Response (ASPR) oversees the fair and equitable allocation of Paxlovid to state and territorial health departments, and select Health Resources & Services Administration (HRSA) funded health clinics. As of January 12, 2022, the U.S. Government had ordered 20 million treatments from Pfizer.

Since December 2021, the U.S. government distributed 264,910​ Paxlovid treatments to the U.S., including 99,980 during the week of Jan. 24.

PAXLOVID Oral Antiviral Side Effects and Drug Interactions

On December 30, 2021, the U.S. NIH published 'Ritonavir-boosted nirmatrelvir (Paxlovid) has significant and complex drug-drug interaction potential, primarily due to the ritonavir component of the combination. Boosting with ritonavir, a strong cytochrome P450 (CYP) 3A inhibitor, is required to increase the exposure of nirmatrelvir to a concentration that is effective against SARS-CoV-2. Ritonavir is an FDA-approved drug that has been used as a pharmacologic boosting agent for certain anti-HIV medications; therefore, there is a large body of literature describing its use with other drugs and its potential for serious and sometimes life-threatening drug-drug interactions. Clinicians who are not experienced in prescribing ritonavir-boosted drugs should refer to resources such as the EUA fact sheet for ritonavir-boosted nirmatrelvir (Paxlovid) and the Liverpool COVID-19 Drug Interactions website for additional guidance. 

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) History

Pfizer developed PF-07321332 by modification of PF-07304814 (Lufotrelvir), a covalent inhibitor. PF-07304814 needs to be administered intravenously, not orally. PF-07321332 is also a covalent inhibitor, but its warhead is a phosphate prodrug of a hydroxyketone.

Pfizer Inc. announced results from the Phase 2/3 EPIC-HR clinical trial on December 14, 2021, showing PAXLOVID (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) significantly reduced the risk of hospitalization or death for any cause by 89% compared to placebo in nonhospitalized, high-risk adult patients with COVID-19 treated within three days of symptom onset. In addition, in a secondary study endpoint, PAXLOVID reduced the risk of hospitalization or death for any cause by 88% compared to placebo in patients treated within five days of symptom onset, an increase from the 85% observed in the interim analysis. 

A scheduled interim analysis announced on November 5, 2021, showed an 89% reduction in risk of COVID-19-related hospitalization or death from any cause compared to placebo in patients treated within three days of symptom onset; 0.8% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization, compared to 7.0% of patients who received placebo and were hospitalized or died.

Pfizer is also investigating an intravenously administered investigational protease inhibitor, PF-07304814, which is currently in Phase 1b multi-dose trial in hospitalized clinical trial participants with COVID-19.

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) Indication

PAXLOVID (PF-07321332) oral antiviral therapy is indicated to prevent the SARS-CoV-2 virus from replicating in human host cells. If authorized or approved, PAXLOVID would be the first oral antiviral of its kind, a 3CL protease inhibitor specifically designed to combat SARS-CoV-2 that could be prescribed as an at-home treatment to high-risk patients at the first sign of infection, potentially helping patients avoid severe illness, which can lead to hospitalization and death. 

The EMA's Committee for Medicinal Products for Human Use issued advice on the use of PAXLOVID™ (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) in December 2021, stating that PAXLOVID can be used to treat adults with COVID-19 who do not require supplemental oxygen and who are at increased risk of progressing to severe disease. The EMA also recommends PAXLOVID should be administered after a diagnosis of COVID-19 and within five days of the start of symptoms. 

The U.S. NIH says 'clinicians who are not experienced in prescribing ritonavir-boosted drugs should refer to resources such as the EUA fact sheet for ritonavir-boosted nirmatrelvir (Paxlovid). Before prescribing ritonavir-boosted nirmatrelvir (Paxlovid) for a patient receiving this immunosuppressant, the patient's provider should be consulted, given the significant drug-drug interaction potential between ritonavir and the narrow therapeutic index agent and because close monitoring may not be feasible.

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) and Pregnant and Breastfeeding Women

Paxlovid is not recommended during pregnancy and in women who can become pregnant and who are not using contraception. In addition, breastfeeding should be interrupted during treatment. These recommendations are because laboratory studies in animals suggest that high doses of Paxlovid may impact the growth of a fetus.

The EUA for Paxlovid suggests that individuals who use products containing ethinyl estradiol for contraception should use a backup, nonhormonal contraceptive method because Paxlovid has the potential to decrease ethinyl estradiol levels. However, the enzyme-inducing effects of Paxlovid that would lead to lower hormone exposure are not expected to be clinically significant during 5 days of therapy and, therefore, would not be expected to decrease contraceptive effectiveness. In addition, ethinyl estradiol is always combined with a progestin for contraception. Progestin concentrations are expected to remain similar or increase when Paxlovid is used concomitantly with combined hormonal contraception, which maintains the effectiveness of the oral contraceptive.

PAXLOVID Oral Antiviral (nirmatrelvir, ritonavir) Genetic

Under the terms of the head license agreement between Pfizer and MPP, announced on November 16, 2021, qualified generic medicine manufacturers worldwide that are granted sub-licenses will be able to supply PF-07321332 in combination with ritonavir to 95 countries, covering up to approximately 53% of the world's population. This agreement includes all low- and lower-middle-income countries, upper-middle-income countries in Sub-Saharan Africa, and countries that have transitioned from lower-middle to upper-middle-income status in the past five years.

PAXLOVID Oral Antiviral Dosage

In the U.S., Paxlovid is available by prescription only and should be initiated as soon as possible after a diagnosis of COVID-19 and within five days of symptom onset. 

PAXLOVID intends 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. In addition, one box contains five blister packs of PAXLOVID, as co-packaged nirmatrelvir tablets with ritonavir tablets, providing all required doses for an entire five-day treatment course.

The EMA says, 'Paxlovid must not be used with certain other medicines, either because its action may lead to harmful increases in their blood levels, or because conversely, some medicines may reduce the activity of Paxlovid itself. The list of medicines that must not be used with Paxlovid is included in the proposed conditions for use. Paxlovid must also not be used in patients with severely reduced kidney or liver function.' On December 30, 2021, the U.S. NIH COVID-19 Treatment Guidelines Panel's Statement on Potential Drug-Drug Interactions Between Ritonavir-Boosted Nirmatrelvir (Paxlovid) and Concomitant Medications was updated.

PAXLOVID Oral Antiviral Ingredients

The two active substances of the medicine, PF-07321332, and ritonavir, are available as separate tablets, should be taken together twice a day for five days.

PAXLOVID Oral Antiviral Price

Pfizer Inc. sold PAXLOVID to the U.S. government for $529 per course in 2021. Through the purchase agreement, the U.S. government will receive 10 million treatment courses for $5.295 billion, with the first courses delivered by the end of 2021, pending EUA.

PAXLOVID Oral Antiviral Payments in the U.S.

In the U.S., Plaxovid is available by prescription only. CMS has released a set of toolkits for providers, states, and insurers to help the health care system prepare and assist in swiftly administering COVID-19 products once they become available. 

PAXLOVID Oral Antiviral Revenues

Pfizer Inc. announced a potential PAXLOVID sale of $5.29 billion to be recognized as revenue in 2021 and 2022. In addition, the company recently raised Full-Year 2021 Guidance for Revenues to a Range of $81 to $82 Billion. And the NYT reported in December 2021, the investment bank SVB Leerink estimated that the drug would bring in $24 billion in global revenue in 2022 and $33 billion in 2023. 

On January 23, 2022, the NASDAQ published - Pfizer: Don’t Discount its Powerful Pipeline and Paxlovid Potential.

PAXLOVID Oral Antiviral News

January 25, 2022 - Media reported India's Subject Expert Committee is requiring local bioavailability and bioequivalence clinical studies and safety data prior to authorizing generic versions of Paxlovid for use in India.

January 22, 2022 - The WSJ reported: As Covid-19 Pills Roll Out, Worry Mounts That Resistance Could Develop.

January 21, 2022 - The journal Nature published a news article: The first crop of antivirals against SARS-CoV-2 is promising. But new drugs will be needed to counter the looming threat of resistance.

January 21, 2022 - Canadian media reported the first shipment of Paxlovid arrived in Ontario.

January 20, 2022 - The Australian Government welcomes the Therapeutic Goods Administration's provisional approval of the first oral Paxlovid® (nirmatrelvir + ritonavir).

January 18, 2022 -  Pfizer Inc. announced results from multiple clinical studies demonstrating the in vitro efficacy of nirmatrelvir, the active main protease inhibitor of PAXLOVID, is maintained against the SARS-CoV-2 virus variant known as Omicron.

January 17, 2022 - The Honourable Filomena Tassi, Minister of Public Services and Procurement, announced Canada has received an initial shipment of 30,400 treatment courses of PAXLOVID, with 120,000 more expected by the end of March 2022.

January 12, 2022 - According to the Kan public broadcaster, the first Paxlovid shipment consisted of 20,000 doses. Israel has signed a deal with Pfizer to purchase 100,000 doses overall, according to Hebrew media reports.

January 10, 2022 - The EMA announced 'Should the additional data submitted with the conditional marketing authorization application be sufficient to conclude that the benefits of Paxlovid outweigh its risks in the treatment of COVID 19, the EMA will liaise closely with the European Commission to fast track the decision granting a conditional marketing authorization in all EU and the EEA Member States.'

January 4, 2022 - Pfizer Inc. confirmed the U.S. government has now ordered a total of 20 million Paxlovid treatments for delivery in 2022.

December 31, 2021 - Dr. June Raine, MHRA Chief Executive, announced "Today we have given our regulatory approval for Paxlovid, a COVID-19 treatment found to cut COVID-19 related hospitalizations and deaths by 89% when taken within three days of the start of symptoms."

December 29, 2021 - Walmart Inc. announced Sam's Club and Walmart pharmacies are ready to receive and dispense Paxlovid as supplies allow.

December 26, 2021 - The Times of Israel announced the Health Ministry authorized Paxlovid.

December 22, 2021 - The U.S. FDA announced a EUA for Paxlovid (nirmatrelvir tablets and ritonavir tablets, co-packaged for oral use) for the treatment of mild-to-moderate COVID-19 in adults and certain pediatric patients with positive results of direct SARS-CoV-2 testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death. Paxlovid is available by prescription only and should be initiated as soon as possible after a diagnosis of COVID-19 and within five days of symptom onset.

December 22, 2021 - Pfizer Inc. announced a new agreement with the United Kingdom government to supply an additional 2.5 million treatment courses of its investigational candidate PAXLOVID™, subject to local authorization. This brings the total amount of treatment courses to 2.75 million.

December 16, 2021 - The EMA advised that Paxlovid should be administered as soon as possible after a diagnosis of COVID-19 and within five days of the start of symptoms. The EMA issued this advice to support national authorities who may decide on the possible early use of the medicine before marketing authorization. If authorized, PAXLOVID could be prescribed as an at-home treatment to high-risk patients at the first sign of infection, potentially helping patients avoid severe illness, which can lead to hospitalization and death. PAXLOVID is also being studied in adults at risk of progressing to severe illness and adults exposed to the virus through household contacts.

December 14, 2021 - Science.org published an article: Pfizer's Paxlovid Holds Up - So Paxlovid looks to have the most effect when you'd want it the most, in patients who are at high risk of bad outcomes.

December 14, 2021 - Pfizer Inc. announced final results from its Phase 2/3 EPIC-HR trial analysis. These results were consistent with the interim analysis announced in November 2021, showing PAXLOVID significantly reduced the risk of hospitalization or death for any cause by 89% compared to placebo in nonhospitalized, high-risk adult patients with COVID-19 treated within three days of symptom onset. In addition, in a secondary endpoint, PAXLOVID reduced the risk of hospitalization or death for any cause by 88% compared to placebo in patients treated within five days of symptom onset, an increase from the 85% observed in the interim analysis.

December 3, 2021 - Filomena Tassi, Canada's minister of public services and procurement, told reporters the government had signed agreements with Pfizer Inc. to buy up to 1 million courses of PF-07321332.

November 29, 2021 - CNBC reported Pfizer estimates it can manufacture 80M treatment courses of Paxlovid, up from 50M projected a few weeks ago.

November 19, 2021 - The EMA announced it is reviewing currently available data on the use of Paxlovid to support national authorities who may decide on its use in emergency use settings before marketing authorization. 

November 18, 2021 - Pfizer Inc. announced an agreement with the U.S. government to supply 10 million treatment courses of PAXLOVID™ (PF-07321332; ritonavir), subject to regulatory authorization beginning later this year and concluding in 2022. Under the agreement terms, Pfizer will receive $5.29 billion from the U.S. government. Pricing for PAXLOVID is based on the principles of advance commitment, volume, equity, and affordability. The company has also entered into advance purchase agreements with several other countries and has initiated bilateral outreach to approximately 100 countries worldwide.

November 16, 2021 - Pfizer Inc. announced it is seeking Emergency Use Authorization of its investigational oral antiviral candidate, PAXLOVID™ (PF-07321332; ritonavir), for the treatment of mild to moderate COVID-19 in patients at increased risk of hospitalizations or death. Rolling submission of non-clinical data for PAXLOVID was initiated with the U.S. FDA in October 2021.

November 16, 2021 - Pfizer Inc. and the Medicines Patent Pool announced the signing of a voluntary license agreement for Pfizer's COVID-19 oral antiviral treatment candidate PF-07321332, which is administered in combination with low dose ritonavir (PF-07321332; ritonavir). The agreement will enable MPP to facilitate additional production and distribution of the investigational antiviral, pending regulatory authorization or approval, by granting sub-licenses to qualified generic medicine manufacturers to facilitate greater access to the global population.

November 13, 2021 - i24News reported an agreement with Pfizer has been reached. The Paxlovid shipment will be despatched as soon as Pfizer receives U.S. FDA approval.

November 10, 2021 - The journal Nature published an article: COVID antiviral pills: what scientists still want to know.

November 8, 2021 - The BMJ published an article: Commenting on the PAXLOVID announcement, England's health and social care secretary, Sajid Javid, said, "If approved, this could be another significant weapon in our armory to fight the virus alongside our vaccines and other treatments, including molnupiravir, which the UK was the first country in the world to approve this week."

November 5, 2021 - Pfizer Inc. announced its investigational novel COVID-19 oral antiviral candidate, PAXLOVID™, significantly reduced hospitalization and death, based on an interim analysis of the Phase 2/3 EPIC-HR randomized, double-blind study of nonhospitalized adult patients with COVID-19. They are at high risk of progressing to severe illness. The scheduled interim analysis showed an 89% reduction in risk of COVID-19-related hospitalization or death from any cause compared to placebo in patients treated within three days of symptom onset (primary endpoint); 0.8% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization (3/389 hospitalized with no deaths), compared to 7.0% of patients who received placebo and were hospitalized or died (27/385 hospitalized with seven subsequent deaths). The statistical significance of these results was high (p<0.0001). Similar reductions in COVID-19-related hospitalization or death were observed in patients treated within five days of symptom onset; 1.0% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization (6/607 hospitalized, with no deaths), compared to 6.7% of patients who received a placebo (41/612 hospitalized with ten subsequent deaths), with high statistical significance (p<0.0001). In addition, in the overall study population through Day 28, no casualties were reported in patients who received PAXLOVID™ as compared to 10 (1.6%) deaths in patients who received placebo.

October 5, 2021 - Australia announced the TGA had granted provisional determination to Pfizer Australia concerning a new combination medicine containing PF-07321332 and ritonavir to treat adult patients with symptomatic, confirmed coronavirus infection. The granting of an interim judgment means that the TGA has decided that Pfizer Australia is now eligible to apply for provisional registration of this treatment in the Australian Register of Therapeutic Goods.

September 27, 2021 - Pfizer Inc. announced the start of the Phase 2/3 EPIC-PEP study to evaluate the investigational novel oral antiviral candidate PF-07321332, co-administered with a low dose of ritonavir, for the prevention of COVID-19 infection. This Phase 2/3 trial is part of a global clinical research program. It enrolls individuals at least 18 years old and live in the same household as those with a confirmed symptomatic SARS-CoV-2 infection.

September 1, 2021 - Pfizer Inc. shared that the first participant has been dosed in a pivotal Phase 2/3 clinical trial to evaluate the safety and efficacy of PF-07321332 – an investigational orally administered protease inhibitor antiviral therapy explicitly designed to combat COVID-19 – in nonhospitalized, symptomatic adult participants who have a confirmed diagnosis of SARS-CoV-2 virus infection and are not at increased risk of progressing to severe illness, which may lead to hospitalization or death. 

July 28, 2021 - Pfizer today provided further details on its oral protease inhibitor program for the treatment of COVID-19. PF-07321332 exhibits potent, selective in vitro antiviral activity against SARS-CoV-2 and other coronaviruses. Additionally, it has demonstrated robust preclinical antiviral effects in human cells in vitro and SARS-CoV-2 infected animals. In Phase 1 pharmacokinetic study in healthy volunteers, PF-07321332 has shown high drug exposure over ten days, - 12 - exceeding the level of exposure predicted to inhibit SARS-CoV-2 viral replication by more than five-fold. Based on these data, Pfizer initiated a Phase 2/3 trial in COVID-19 patients in July 2021. Data from the trial are expected in the fourth quarter of 2021.

May 4, 2021 - Pfizer Inc. published today its 'Key Near-term Potential Milestones for COVID-19 Vaccine Program (2021)' on slide #8 within its financial report.

April 7, 2021 - Chemical & Engineering News published: Pfizer unveils its oral SARS-CoV-2 inhibitor.

March 23, 2021 - Pfizer Inc. announced that it is progressing to multiple ascending doses after completing the dosing of single ascending doses in a Phase 1 study in healthy adults to evaluate the safety and tolerability of an investigational, novel oral antiviral therapy for SARS-CoV-2, the virus that causes COVID-19. This Phase 1 trial is being conducted in the United States.

PAXLOVID PF-07321332 Protease Inhibitor Antiviral Clinical Trials

A Phase 1, double-blind, sponsor open, single, and multiple ascending dose study evaluates the safety, tolerability, and pharmacokinetics of PF-07321332 in healthy participants.

ClinicalTrials.gov Identifier: NCT04960202 - The purpose of this Phase 2/3 study is to determine whether PF-07321332/ritonavir is safe and effective for the treatment of adults who are ill with COVID-19 and do not need to be in the hospital but are at an increased risk of developing severe illness. A provision will be made throughout the study period to allow study visits to be conducted at a participant's home or another non-clinic location if available. The total study duration is up to 24 weeks. Estimated Primary Completion Date: October 5, 2021. Last update date: September 1, 2021.

The Phase 2/3 EPIC-PEP trial is a randomized, double-blind, placebo-controlled study and will enroll up to 2,660 healthy adult participants aged 18 and older. Participants will be randomly assigned (1:1:1) to receive PF-07321332/ritonavir or placebo orally twice daily for 5 or 10 days. The primary objective will assess safety and efficacy to prevent confirmed SARS-CoV-2 infection and its symptoms through Day 14. PF-07321332 is an oral antiviral SARS-CoV-2-3CL protease inhibitor, which has an encouraging preclinical profile, including potent in vitro antiviral SARS-CoV-2 and broad coronavirus activity. Results from the Phase 1 clinical trial demonstrated that PF-07321332 was safe and well-tolerated.

For more information on the EPIC Phase 2/3 clinical trials for PAXLOVID, visit clinicaltrials.gov.