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- The Pfizer drug now being studied is structurally different from ivermectin.
Ivermectin, an anti-parasite drug sometimes used to treat horses, has not been proven effective as a treatment for COVID-19.
Nevertheless, the Zero Hedge blog claims that Pfizer is testing a drug to prevent COVID-19 that is essentially the same as ivermectin. The blog suggests, without evidence, that ivermectin has prevented COVID-19 deaths.
A headline on Zero Hedge, which we’ve fact-checked before, alluded to ivermectin by stating:
"Pfizer Launches Final Study For COVID Drug That's Suspiciously Similar To 'Horse Paste.’"
The post’s reference to "horse paste" seems to be a reference to criticism that ivermectin is only for deworming horses. It is used in animals, but it has also been approved for use in humans, just not as a COVID-19 cure.
The blog post is based on an article from the Reuters news agency about a Pfizer drug known as PF-07321332. The article said Pfizer has begun a study of the pill in up to 2,660 healthy adults who live in the same household as someone with a confirmed symptomatic COVID-19 infection.
Pfizer described the drug as a protease inhibitor, which is "designed to block the activity of the main protease enzyme that the coronavirus needs to replicate." That would stop symptoms from worsening, a spokesperson said.
Zero Hedge seized on the protease inhibitor fact, claiming "that's exactly what ivermectin" does.
Pfizer’s protease inhibitor is not similar to that of an animal medicine and does not use the same mechanism, a Pfizer spokesperson told us.
Benjamin Neuman, chief virologist at Texas A&M University's Global Health Research Complex, said ivermectin’s main job is to block ion channels that parasites use to store up positively and negatively charged atoms. SARS-CoV-2 does not have any ion channels like the ones that ivermectin blocks, so there is not an obvious way for ivermectin to work in COVID-19, he said.
Lab studies indicate that ivermectin might inhibit replication of SARS-CoV-2, but the mechanism is not known and may be more general in nature, said virologist Robert Garry of the Tulane University School of Medicine.
In contrast, PF-07321332 is a molecule that sticks to an important part of the SARS-CoV-2 main protease, which is very important for virus growth, said Neuman. Blocking the main protease essentially stops all the other virus proteins from working, which is why drugs like PF-07321332 have a lot of potential as antiviral therapies, he said.
The Pfizer pill's protease inhibitors are "highly specific," designed to stop replication of the coronavirus, and that makes it quite different from ivermectin, said Garry.
"So no reason to call the Pfizer drug ‘Pfizermectin,’" Garry said. "Clever, but no basis in fact."
Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, said, "It’s unclear what mechanism of action ivermectin has" when it comes to SARS-Cov2. There is at least one study postulating it blocks the viral protease, he said, but "none of this is clear and has to be coupled with the fact that there has not been evidence" that ivermectin is effective in treating COVID-19.
"The Pfizer compound, by contrast, was designed explicitly to target the protease of the virus," he said. "Ivermectin is an anti-parasitic drug that has a distinct mechanism of action against parasites and may happen to have some similarities, by chance, with the Pfizer compound."
As we have reported, some studies have raised the possibility that ivermectin might work in treating COVID-19. But researchers say there is no conclusive evidence that it is an effective COVID-19 treatment.
Ivermectin is not approved for COVID-19 prevention or treatment by the U.S. Food and Drug Administration. The FDA has also gone a step further, recommending against its use for COVID-19.
Nevertheless, prescriptions for ivermectin have risen 24-fold since before the pandemic.
Pfizer is the maker of the only COVID-19 vaccine used in the United States that has been approved by the FDA. The Moderna and Johnson & Johnson vaccines are being given under an emergency use authorization.
A blog post claimed: "Pfizer launches final study for COVID drug that's suspiciously similar to 'horse paste'" ivermectin.
The drug Pfizer is testing to treat COVID-19 is structurally different from ivermectin, which has not been proven to prevent or treat COVID-19.
We rate the post False.
Zero Hedge, "Pfizer Launches Final Study For COVID Drug That's Suspiciously Similar To 'Horse Paste,'" Sept. 28, 2021
Reuters, "Pfizer begins study of oral drug for prevention of COVID-19," Sept. 27, 2021
Pfizer, news release, Sept. 27, 2021
Email, Benjamin Neuman, chief virologist at Texas A&M University's Global Health Research Complex, Sept. 30, 2021
Email, Jerica Pitts, director, Pfizer global media relations, Sept. 30, 2021
Email, Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, Sept. 30, 2021
Full Fact, "Pfizer’s new trial drug is not ivermectin in disguise," Sept. 21, 2021
Email, virologist Robert Garry of the Tulane University School of Medicine, Sept. 29, 2021
PolitiFact, "No evidence yet concluding that ivermectin is an effective COVID-19 treatment," Aug. 10, 2021
PolitiFact, "A Nobel Prize and a horse dewormer: Explaining the controversy over ivermectin and COVID-19," Sept. 8, 2021
USA Today, "Fact check: Pfizer is testing a drug to treat COVID-19 infections. It's not tied to vaccinations," Sept. 8, 2021
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