Fact Check

'Pfizermectin'? Is Pfizer's New Drug Just Ivermectin in Disguise?

"Protease inhibitors" are a class of antiviral drugs that have been used to treat HIV/AIDS, hepatitis C, and possibly COVID-19.

Published Sept. 30, 2021

Pfizer is developing an oral COVID-19 drug that is just a clone of the anti-parasite drug Ivermectin.

Pfizer is developing an oral drug to prevent COVID-19 infections. This drug, currently known as PF-07321332, is a protease inhibitor "designed to block the activity of the main protease enzyme that the coronavirus needs to replicate." This drug is not a repackaged version of ivermectin.

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In September 2021, a number of news outlets reported on a new oral drug that was being developed by Pfizer to combat the COVID-19 pandemic. As these reports circulated online, some social media users jokingly dubbed the new drug "Pfizermectin," a combination of the company's name and the drug ivermectin — a medication that was developed to treat parasite infections that has been the source of both confusion and controversy — and claimed that Pfizer was copying or cloning the drug.

Why Is Ivermectin Controversial?

Before we get to "Pfizermectin," let's look at why ivermectin has become controversial.

Ivermectin is used to treat parasitic worms in both humans and farm animals. The developers of this drug won the Nobel Prize in 2015 after the drug was found to be quite successful at fighting River Blindness and Lymphatic Filariasis. While this drug has been approved by the Food and Drug Administration (FDA) as a treatment for parasite infections, it has not been approved as a treatment for COVID-19.

Some studies, however, have suggested that ivermectin may have potential as a treatment for COVID-19, but those studies have largely been inconclusive. This has still led some people to try to self-medicate with the drug, and in some cases, for people to self-medicate with the horse version of the drug. In short, ivermectin is not (yet) an approved treatment for COVID-19.

Is Pfizer's New Drug Just Repackaged Ivermectin?


The above-displayed tweet claims that Pfizer's new drug, PF-07321332, is simply ivermectin with a new name. That is not true.

The tweet then claims that Pfizer is rebranding this drug so that it can make the medication more expensive. That's nonsensical.

Those spreading this claim appear to be under the belief that "Big Pharma" is stealing an independently produced drug, partnering with government agencies to get the drug quickly approved, and then hiking up the price as it goes to market. But there are a few problems with this theory.

For one, ivermectin is already produced by the "Big Pharma" company Merck. If Pfizer was truly copying this drug, it seems plausible that Merck would be pushing back in the press or in lawsuits. But that hasn't been the case.

Furthermore, ivermectin is already an approved drug by the FDA for its originally intended use: to treat parasite infections. The drug has not been approved by the FDA to treat COVID-19 because the drug has not been proven to be an effective treatment against COVID-19.

But Ivermectin and Pfizer's New Drug Are Both 'Potent Protease Inhibitors,' Right?

A more nuanced version of the "Pfizermectin" rumor claims that both Pfizer's new drug and ivermectin act as "potent protease inhibitors," which, according to social media users, basically makes them the same drug. But that's not the case.

Ivermectin was not developed as a protease inhibitor. This claim comes from a March 2021 study that investigated the efficacy of ivermectin as an antiviral drug. That study found that ivermectin was a "blocker of viral replicase, protease and human TMPRSS2."  

But protease inhibitors are a class of antiviral drugs that have been used to treat HIV/AIDS and Hepatitis C. In other words, there are several different drugs that act as a protease inhibitors ("Protease is an enzyme in the body," according to Healthline, and "Protease inhibitor drugs block the action of protease enzymes"). Just because two drugs may perform a similar function does not mean that they interchangeable or identical.

A spokesperson for Pfizer told us:

Pfizer’s protease inhibitor is not similar to that of an animal medicine and is not the same mechanism. In the past, protease inhibitors revolutionized the treatment of HIV and Hepatitis C. Applying this powerful and potent mechanism of action to COVID-19 could alter the course of the pandemic. For COVID-19, protease inhibitors are designed to block the activity of the SARS-CoV-2 protease, which is an enzyme the virus needs to multiply and replicate itself in the body, and as a result, stop symptoms from worsening.

Dr. Stephen Griffin, a virologist and associate professor at Leeds Institute of Medical Research, told Full Fact that Pfizer's new drug was "nothing like" ivermectin, and that the two drugs were "extremely structurally different."

What's Pfizer's New Drug?

Pfizer is currently conducting trials on a new oral drug, currently known as PF-07321332, to fight the COVID-19 pandemic. The company said in a statement that the "novel oral antiviral candidate PF-07321332" would be co-administered with a "low dose of ritonavir," another antiretroviral protease inhibitor, to prevent COVID-19 infections.

Pfizer said in a statement: "Protease inhibitors, like PF-07321332, are designed to block the activity of the main protease enzyme that the coronavirus needs to replicate."

Dr. Mikael Dolsten, Pfizer's chief scientific officer and president for Worldwide Research, Development, said:

"If successful, we believe this therapy could help stop the virus early – before it has had a chance to replicate extensively – potentially preventing symptomatic disease in those who have been exposed and inhibiting the onset of infection in others ... 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.”


Chaccour, Carlos, et al. “Ivermectin and COVID-19: Keeping Rigor in Times of Urgency.” The American Journal of Tropical Medicine and Hygiene, vol. 102, no. 6, June 2020, pp. 1156–57. PubMed Central, https://doi.org/10.4269/ajtmh.20-0271.

Commissioner, Office of the. “Why You Should Not Use Ivermectin to Treat or Prevent COVID-19.” FDA, Sept. 2021. www.fda.gov, https://www.fda.gov/consumers/consumer-updates/why-you-should-not-use-ivermectin-treat-or-prevent-covid-19.

Garfinkel, Noah. “Pfizer Testing Oral Pill That Could Prevent COVID Infection.” Axios, https://www.axios.com/pfizer-tests-oral-pill-covid-infection-prevention-82292abc-1b7a-4109-8abb-a15e02ba7a0e.html. Accessed 30 Sept. 2021.

Choudhury, Abhigyan, et al. “Exploring the Binding Efficacy of Ivermectin against the Key Proteins of SARS-CoV-2 Pathogenesis: An in Silico Approach.” Future Virology, p. 10.2217/fvl-2020–0342. PubMed Central, https://doi.org/10.2217/fvl-2020-0342.

“Guide to Protease Inhibitors for HIV.” Healthline, 29 Mar. 2018, https://www.healthline.com/health/hiv-aids/protease-inhibitors.

Pfizer Initiates Phase 1 Study of Novel Oral Antiviral Therapeutic Agent Against SARS-CoV-2 | Pfizer. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-initiates-phase-1-study-novel-oral-antiviral. Accessed 30 Sept. 2021.

Pfizer Starts Global Phase 2/3 EPIC-PEP Study of Novel COVID-19 Oral Antiviral Candidate for Post-Exposure Prophylaxis in Adults | Pfizer. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-starts-global-phase-23-epic-pep-study-novel-covid-19. Accessed 30 Sept. 2021.

“Pfizer’s New Trial Drug Is Not Ivermectin in Disguise.” Full Fact, 21 Sept. 2021, https://fullfact.org/online/new-protease-inhibitor/.

“Springfield Farm Stores See Increase in Ivermectin Sales as COVID-19 Pandemic Continues.” Springfield News-Leader, https://www.news-leader.com/story/news/local/2021/08/30/springfield-missouri-farm-stores-see-increase-ivermectin-sales-covid-19-horse-dewormer-fda-warning/5601496001/. Accessed 30 Sept. 2021.

Dan Evon is a former writer for Snopes.

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