Vaccine Info

PF-07321332 Oral Antiviral

Authored by
Last reviewed
October 5, 2021

PF-07321332 Protease Inhibitor Antiviral Description

Pfizer's PF-07321332 is an oral antiviral therapeutic targeting the SARS-CoV-2 betacoronavirus to prevent COVID-19. In addition, Pfizer's PF-07321332 is a protease inhibitor that has demonstrated potent in vitro antiviral activity against SARS-CoV-2 and activity against other coronaviruses, suggesting potential for use in the treatment of COVID-19, as well as potential use to address future coronavirus threats, says Pfizer.

By inhibiting the main protease, PF-07321332 prevents the virus from cleaving long protein chains into the parts it needs to reproduce itself.

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, both alone and with other antivirals. 

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.

PF-07321332 is the first orally administered coronavirus-specific investigational protease inhibitor to be evaluated in clinical studies. There is no orally administered therapy currently approved for the post-exposure or pre-emptive treatment of COVID-19, says Pfizer.

Mikael Dolsten, M.D., Ph.D., Chief Scientific Officer and President, Worldwide Research, Development, and Medical of Pfizer, commented in a press release issued on March 23, 2021, "We have designed PF-07321332 as a potential oral therapy that could be prescribed at the first sign of infection, without requiring that patients are hospitalized or in critical care. At the same time, Pfizer's intravenous antiviral candidate is a potential novel treatment option for hospitalized patients. Together, the two have the potential to create an end-to-end treatment paradigm that complements vaccination in cases where the disease still occurs."

Dr. Dolsten stated in a press release issued on September 27, 2021, "Given the continued emergence and evolution of SARS-CoV-2 variants and their immense impact, we continue to work diligently to develop and study new ways that our investigational oral antiviral candidate could potentially lower the impact of COVID-19, not only on patients' lives but also the lives of their families and household members."

Chemical Formula: C23H32F3N5O4; DrugBank Accession Number DB16691.

To learn more, please visit New York-based Pfizer Inc. at (NYSE: PFE)

PF-07321332 Protease Inhibitor Antiviral Indication

PF-07321332 Antiviral Therapeutic is indicated to prevent the SARS-CoV-2 virus from replicating in human host cells. If successful, PF-07321332 can be prescribed to patients before they require hospitalization. Protease inhibitors, like PF-07321332, are designed to block the activity of the main protease enzyme that the coronavirus needs to replicate.

PF-07321332 Protease Inhibitor Antiviral News

October 5, 2021 - Australia announced the TGA had granted provisional determination to Pfizer Australia in relation to a new combination medicine containing PF-07321332 and ritonavir, for the treatment of adult patients with symptomatic, confirmed coronavirus infection. The granting of a provisional determination means that the TGA has made a decision 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 and is enrolling individuals who are at least 18 years old and live in the same household as an individual 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 designed specifically to combat COVID-19 – in non-hospitalized, 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 effect in human cells in vitro and in SARS-CoV-2 infected animals. In Phase 1 pharmacokinetic study in healthy volunteers, PF-07321332 has shown high drug exposure over 10 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.

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.

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. 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 for the prevention of 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 pre-clinical 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.

Clinical Trials

No clinical trials found