The Potential of Antivirals

Does the secret to an effective COVID-19 treatment lie in a protease inhibitor?

At Pfizer, we are evaluating an antiviral compound – a protease inhibitor identified by Pfizer scientists in 2003 – as a treatment for COVID-19. We believe this potential treatment, which interrupts the virus’ ability to multiply, could be a first-in-class opportunity to help treat COVID-19 patients. Today, there are no FDA approved antiviral treatments for COVID-19 patients.

Success against COVID-19 will likely require effective antiviral treatments for patients with the disease, and speed is of the essence as we work to attempt to lower the impact of COVID-19 on patients’ lives.

When COVID-19 emerged, we evaluated our robust portfolio of therapeutics and screened some of the compounds from our legacy SARS (severe acute respiratory syndrome) protease inhibitor pre-clinical program with the hopes of identifying a compound that could potentially be used to treat COVID-19 and/or its symptoms. SARS is a viral respiratory illness caused by a coronavirus, which is part of the same family of viruses that cause COVID-19. Specifically, SARS-CoV-1 causes SARS while SARS-CoV-2 is the virus that causes COVID-19.

One of the most promising compounds identified was a compound with antiviral activity, specifically a compound which slows or potentially stops a virus from replicating. The identified compound is a protease inhibitor, and it appears to be work best at inhibiting the proteases produced by coronaviruses. It is hoped that may help reduce the symptoms associated with COVID-19 and the risk of significant health complications for patients.

Developing potential COVID-19 treatments is only possible through the dedicated work of our research partners and individuals who volunteer to take part in clinical trials. We are grateful to each of the 9 clinical trial investigators and their study teams who are partnering with us in this effort and to all of the participants who have volunteered, and will volunteer, to help make a difference for society.

We continue to be committed to diversity in our clinical trial and ensuring that individuals from communities that have been most affected by COVID-19 have the opportunity to participate.

What kind of antiviral is Pfizer investigating?

Pfizer is investigating a protease inhibitor called PF-07304814. The compound has been shown in pre-clinical studies to inhibit proteases used by coronaviruses to replicate, inhibiting both the coronavirus responsible for causing SARS in 2003 and the coronavirus which is causing COVID-19 today.

How do antivirals contribute to the treatment of COVID-19?

Certain antivirals help slow or stop a virus from replicating and thereby help reduce the symptoms associated with COVID-19 and the risk of significant health complications. The Pfizer investigational antiviral compound is a type of compound called a protease inhibitor, which interferes with part of the coronavirus needed for the virus to make copies of itself. This compound is currently being investigated for potential treatment of COVID-19.

What is the clinical status of PF-07304814?

Pfizer initiated a Phase 1b trial for PF-07304814 in September. The study will evaluate the safety, tolerability and pharmacokinetics of PF-07304814 in patients with SARS-CoV-2 virus infection and with mild-to-moderate symptoms, PF-07304814 is a phosphate prodrug that when administered intravenously is metabolized to the active compound PF-00835321, which is shown to be a very potent inhibitor of the SARS-CoV-2 coronavirus (or COVID-19) in pre-clinical studies. The study is double-blind and placebo-controlled, meaning approximately half of the participants will receive the study medicine intravenously and the other half will receive a placebo (an injection with no active ingredient) and neither participants nor investigators know who is getting which. If the study is successful, we anticipate starting a Phase 2/3 trial to better understand the safety and efficacy of the compound in a larger patient population.

When do you expect to announce results from the Phase 1b study?

We initiated the Phase 1b study in September and recently began dosing. We expect this trial to readout as early as late 2020 and, subject to the outcome of the on-going trial, we are planning a pivotal Phase 2/3 trial to begin in 2021, with a projected approval in the second half of 2021.

Is Pfizer investigating other antiviral candidates for COVID-19?

At this time, Pfizer is evaluating only its protease compound PF-07304814 in a Phase 1b study.