At the height of the COVID-19 pandemic, the name of a drug most people had never heard of before was suddenly on everyone’s lips. An off-patent antiparasitic blessed by the World Health Organization, which had included it on its list of essential medicines, and recognized in its importance by a Nobel Prize, ivermectin was the cool uncle of the pandemic. You didn’t have to obey the parental rules of the government or line up for a vaccine you were told had been developed a little bit too quickly.
Ivermectin was safe, cheap, and lauded by the scientific establishment, and it was reported to both prevent and treat COVID-19... if COVID-19 was even real, many who took ivermectin undoubtedly told themselves.
And there were studies proving its efficacy against the coronavirus! Except that when these early studies were scrutinized, glaring problems became evident. Plagiarized text, mathematically impossible results, and soon allegations that an entire experiment had never even taken place. When ivermectin was properly put to the test against the virus, it was clear that it simply did not work. Off-label prescriptions for the drug waned in 2023... but they started up again the following year and increased some more in 2025. What is it being prescribed for, if not for the parasitic infections against which it has been shown to work?
We are unfortunately straying away from drugs being approved for this or that condition based on scientific evidence; health interventions have now been politicized, and ivermectin is the supreme example. Vaccines are liberal and ivermectin is MAGA. Soybeans are leftists and beef tallow is on the right. Mainstream medicine is for centrist sheeple, while functional medicine is for the conservative vanguard. The epicentre of this politicization is the United States, but its ripple effects can be felt anywhere with an Internet connection.
So, what do you do if you started a business selling ivermectin during the pandemic but have no one to sell it to? You put an ear to the ground and listen.
In January 2025, Google searches for “ivermectin cancer” shot up. Actor and director Mel Gibson had just appeared on The Joe Rogan Experience, one of the most popular shows in the world, to tell Rogan that he blindly believes that every disease has a natural cure. “I’ll tell you a good story,” he says, “I have three friends. All three of them had stage four cancer. All three of them don’t have cancer right now, at all. And they had some serious stuff going on.” When Rogan asks him what they took, Gibson acts like a child with a secret who was told by his parents not to spill the beans. “They took some... what you’ve heard they’ve taken.” Rogan says, “Ivermectin,” and Gibson smiles and nods emphatically.
On the social media platforms X and Telegram, cancer treatment protocols focused on ivermectin are advertised and right-wing wellness influencers sing its merits. Earlier this year, the U.S. federal cancer research agency announced it would study the antiparasitic drug as a potential treatment for cancer.
Ivermectin, which was ridiculed as “horse paste” for its popular veterinary use, is being positioned as the chemotherapy of the anti-woke. Studies show that it does have anti-tumour effects, yes, but digging into these scientific papers is an educational journey into why we can’t take a study at face value.
They’re the same picture
The story of ivermectin begins in the earth. A Japanese microbiologist, Satoshi Ōmura, found new bacteria in soil samples and managed to cultivate them in the lab. This was of interest because bacteria can produce compounds that can kill other microorganisms, which can lead to new pharmaceutical drugs. A parasite expert working in the U.S., William C. Campbell, acquired Ōmura’s bacterial cultures and was able to isolate a new compound, which was then made more effective by chemical modification in the lab. This modified compound was named ivermectin. It was demonstrated to work really well against certain parasites, first in animals, then in humans, and it would earn the co-discoverers the Nobel Prize in Physiology or Medicine in 2015, alongside Tu Youyou who discovered artemisinin’s efficacy against malaria.
It’s worth pointing out that Campbell was, at the time of his discovery, working for the research arm of pharma giant Merck & Co., Inc.—a reminder that pharmaceutical companies do not ignore nature, as many conspiracy theorists love to say; rather, they study it and refine its products to market medications with well-established safety profiles.
Ivermectin has been approved for a number of conditions, but cancer is not one of them. If you search the literature for “ivermectin” and “cancer,” you will find studies, almost all of them in cells or in laboratory animals, but publishing the results of a study is just the first step. We have to look at what happens after.
Take this 2021 paper from an American team. At the time of publication, it looked really promising. Cancer can often evade our immune system, and researchers have tried for decades to get our immune cells to detect a tumour and attack it. This study seemed to show that when mice were injected with breast cancer cells and were then given ivermectin, some of these cancer cells died in such a way that it got picked up by the mouse’s immune system, which rallied its troops and infiltrated the remaining tumour.
The authors refer to this as turning a “cold” tumour (which has not been infiltrated by immune cells) into a “hot” tumour, and all that because of a readily available antiparasitic drug. The icing on the cake is that this study was not hastily done in someone’s basement; it involved major research institutes like MIT and the Howard Hughes Medical Institute, supported by the Department of Defense and the National Cancer Institute, and the resulting paper was published in partnership with the Breast Cancer Research Foundation.
Big names... and yet there was a problem. On PubPeer, a site where researchers can highlight flaws in published studies, eagle-eyed observers noticed a graphic with error bars that appeared to have been manipulated, as well duplicated images. A duplicated image means that, for example, a photo meant to show tumours in a control mouse and another photo showing tumours in a mouse that received ivermectin are revealed to be the exact same photo. The study’s main author called it an “oversight” by a postdoctoral fellow who had worked on the paper and had since left the lab. An expression of concern was published by the journal, advising readers to interpret the paper’s results with caution, and the paper’s authors claimed that the original data was somehow no longer available. Then came more reports of apparently duplicated images in the paper, and it’s unclear to me if this paper can even be trusted.
Another paper, this one from a Chinese team that claimed to show that ivermectin could make chemotherapy more effective in a type of liver cancer, was retracted by its journal when similar image duplications were detected and when the main author listed on the paper said he hadn’t even been aware of the paper itself.
History appears to be repeating itself, as early signals of ivermectin working against COVID-19 were similarly contaminated by significant errors and scientific impropriety. Entire participant data were copied and pasted into other participants in one study’s table of results; in another, some of the patients had died before the trial had even started. Data detectives found unlikely numbers and incorrect percentages, and a few promising papers were retracted from publication because they were revealed to be untrustworthy. It may not be that research into ivermectin is particularly prone to misconduct, though. As Jack Lawrence, one of these data detectives and currently a final-year Ph.D. student at City St. George’s, University of London told me, “I think the increased scrutiny of ivermectin has identified bad science that otherwise would have been missed.” Then again, he adds that the potential for contrarians to profit off of ivermectin “might be an incentive to produce positive results for the drug.”
Jack and I have been friends since his initial foray into denouncing ivermectin-related pseudoscience in 2021, and he is in an interesting position: his doctorate is precisely on the potential that ivermectin has as a cancer drug. By day, he performs difficult and frustrating laboratory experiments to figure out if ivermectin could indeed be useful to an oncologist. By night, he witnesses the foolish claims made online by conspiracy theorists who have lost trust in conventional medicine. And he sees the very same evidence he rolls his eyes at in the lab being presented on social media as unassailable proof of the drug’s anti-cancer might.
Having anti-tumour activity is no slam dunk
For believers in the anti-cancer properties of ivermectin, one paper rises above the fray. But make no mistake: it’s not a scientific paper so much as a promotional vehicle for The Wellness Company’s private, alternative, virtual healthcare. TWC was founded by a Canadian entrepreneur, Foster Coulson, who was influenced by his meeting with a doctor who was pushing hydroxychloroquine during the pandemic. It has since recruited Dr. Peter McCullough, whose board certification was revoked following his promotion of COVID-19 misinformation. On its store page, you can buy whipped tallow cream; an unproven supplement said to detoxify you from the coronavirus’ spike protein; and, of course, ivermectin. Now, The Wellness Company is writing up scientific papers.
Published earlier this year, the paper in question is essentially a survey of The Wellness Company’s client base. People with all sorts of different cancers were sent ivermectin and reported if their tumours subsequently shrank or enlarged.
Cancer is not a single disease but a family of diseases. Ivermectin could be effective against one type of cancer and not the rest, but there is no easy way to sort through this here. There is no control group—a fatal flaw—and the participants were also undergoing all sorts of medical procedures (chemotherapy, radiation therapy, surgery) and more questionable ones (keto diets, hyperbaric oxygen therapy, and dietary supplements). The authors of the paper are all employed by The Wellness Company and include Dr. Peter McCullough as well as Dr. Drew Pinsky, the former host of the radio show Loveline who has reinvented himself as a COVID contrarian. Unwilling to pay for a medical illustrator, the team prompted a generative AI to create images for their paper, which they claim they altered to ensure accuracy.
None of this should be convincing, nor should the large number of review papers on the link between ivermectin and cancer change your mind. As Jack Lawrence joked, there are almost as many review papers as actual studies of ivermectin’s anti-cancer potential. Writing a review paper is an easy way for researchers to pad their CV, and their sheer accumulation can convince the casual reader that there really is something there. All you have to do is regurgitate the following information: this is what ivermectin is, this is how it was discovered, these are some interesting properties that have been seen in the lab, and these are the few studies that make us think that maybe, maybe it could work for cancer, but more studies are needed. Lather, rinse, repeat.
The one trial done in humans is still unfolding and should end soon. Its preliminary results are far from encouraging: one participant’s cancer remained stable, one had a partial response, and the cancer of the six others worsened. Importantly, this trial is not testing ivermectin on its own but in combination with an approved targeted therapy to see if the antiparasitic can increase its potency.
Everything else is lab work. And, sure, it looks impressive on casual reading. There is evidence that, in cancer cells cultured in the lab or in mice with tumours, ivermectin can provoke a kind of cell suicide inside the tumour, and arrest a cell cycle out of control, and inhibit pro-cancer signals, and call upon the immune system to find a hidden tumour. It was found to interact with a number of important molecules inside of cells, like the mTOR pathway and RNA helicase. But none of this is special.
Ivermectin is part of a larger project to repurpose drugs that have already been approved for one thing to see if they can also be used as cancer treatments. At least 298 of these drugs have been found to have some kind of anti-tumour activity in the lab. So far, very few of them have convincingly been shown to help treat specific types of cancer: thalidomide for multiple myeloma and arsenic trioxide for acute promyelocytic leukemia. If we zoom out of cancer research and look at drug development as a whole, it has been estimated that, these days, 19 out of every 20 drugs that look promising enough in the lab to begin testing in humans will fail to show efficacy and safety in our bodies. Only one in 20 successfully navigates this obstacle course. The human body is not a carpet of cells in a plastic dish.
Ivermectin is just one of many such drugs showing interesting properties in the lab, not the Excalibur that Robert F. Kennedy Jr’s MAHA movement wants it to be. And even if ivermectin is ever shown to be effective in some capacity against one specific cancer, it will not mean that this cancer is caused by parasites, contrary to what some influencers are insinuating. In this context, ivermectin would likely work because of its antitumor activity or its ability to make a cancer treatment more effective, not because of its antiparasitic capabilities.
You may not care that it has not been proven to work against cancer. You may want to take it regardless because you are desperate and have been told that it is safe.
Should you?
Nothing is ever 100% safe
It is true that ivermectin has a wide margin of safety, meaning that there is a lot of room between the dose that is typically effective and a dose that causes severe side effects.
For its approved uses, it is usually prescribed at doses between 0.15 and 0.20 milligram per kilogram of body weight. This means that an average man weighing 84 kilos (185 pounds) would be prescribed 12.6 to 16.8 milligrams, and an average woman weighing 70 kilos (154 pounds), 10.5 to 14 milligrams. Most people on ivermectin report no side effects, but when your body is already dealing with cancer, does that change? All we have right now are 26 individual reports of children and adults with various cancers who happened to catch a parasitic infection that was treated using ivermectin, and in those cases the drug was well tolerated.
However, calls to poison centres specifically for ivermectin doubled in the United States between 2024 and 2025. Some people were taking veterinary preparations of ivermectin, which can contain impurities and varying concentrations that are better tolerated by animals than by humans. Underground manufacturers of the drug have been discovered and it’s unclear how safe their preparations are. Large doses—often listed in online protocols for cancer patients—can cause movement disorders, low blood pressure, seizures, comas, and even death.
Ivermectin has the potential to worsen the side effects of actual cancer treatments and to interact with other drugs. As Jack pointed out in his article for The Skeptic magazine, ivermectin is broken down in the body by a specific liver enzyme which is also responsible for metabolizing certain chemotherapeutic drugs. There is only so much of this enzyme available: jam it up with ivermectin and there won’t be enough of it to process the chemotherapy. This means that otherwise effective cancer drugs could get cleared slower than intended, leading to more side effects and potentially less effectiveness.
And if you are taking ivermectin and want to participate in a clinical trial for a new cancer intervention, you may no longer be eligible. Trials are about minimizing variables to figure out if something works. If patients are also taking other drugs that could be influencing the results, they are likely to be excluded.
Ivermectin die-hards will sweep these concerns aside as conspiracies emanating from Big Pharma. After all, ivermectin’s patent has run off, so there’s no money to be made on this potential anti-cancer revelation, right? While its patent expired in 1997, a paper published by co-discoverer Ōmura in 2011 revealed annual sales in excess of US$ 1 billion, in large part because of its widespread veterinary use. Acetylsalicylic acid, the active ingredient in Aspirin, is also off-patent, but that hasn’t stopped pharmacies from selling countless bottles annually.
And being off-patent doesn’t mean that pharmaceutical research into it suddenly ceases. Clearly, it is being studied, and while funding this research may not be as easy, it is possible: Jack Lawrence’s own doctoral research is proof enough. He tells me that funds to study off-patent drugs can come from government entities, academic hospitals, charities, private philanthropic foundations, patient advocacy groups and, yes, even pharmaceutical companies, which sometimes receive regulatory exclusivity to sell a drug or a specific formulation of it, or which may tweak their molecule slightly to earn a new patent.
I am reminded of metformin, a popular diabetes drug the patent of which has also run out. When I was in grad school studying skin cancer, there were laboratories around ours actively studying whether or not metformin could be repurposed to fight cancer. But when human trials were conducted, what had seemed promising in the lab turned into a major disappointment.
Pre-clinical studies—meaning experiments not conducted in humans—are necessary but their promises should not be endorsed in the clinic. If we care about evidence, we must wait for rigorous trials done in humans and for approvals by trustworthy regulatory agencies. Jack Lawrence, despite being a skeptic, would love for ivermectin to work against cancer: “Not least because it would be very helpful for my academic career.” But as of today, he is quick to remind me, “we lack reliable clinical evidence.”
Unfortunately, we now live in the era of people shopping for medical treatment based on anecdotes, vibes, and political affiliation. While the medical profession and its research arm have spent decades carefully constructing evidence-based algorithms for what is the best first-line therapy, then second-line, then third-line, many patients are snapping up medical products based on what they hear is trending online. Oh, ivermectin was last season’s cancer treatment? Now it has to be combined with fenbendazole, which is only approved for veterinary medicine? In the shopping basket they go.
Don’t be fooled by encouraging results in laboratory experiments. On social media, they get transformed into fad diets, and there’s always someone at the other end profiting from your despair.
Take-home message:
- Ivermectin is an antiparasitic drug that some claimed worked against COVID-19 (which we know is not true) and which is now being positioned as a cancer cure “they” don’t want you to know about.
- Ivermectin is just one of a long list of drugs that show interesting potential in the lab to help treat cancer, but very few drugs that show promise in the lab are revealed to be safe and effective in humans.
- There is currently no good scientific evidence demonstrating that ivermectin can treat a certain type of cancer or help make chemotherapy more effective, although future studies could theoretically change this.
- While ivermectin is a relatively safe drug to take, cancer patients should know that the “protocols” they find online may recommend very high doses that can cause severe side effects; that taking ivermectin while undergoing cancer therapy may alter how your body processes otherwise effective cancer drugs; and that underground laboratories are manufacturing ivermectin to questionable standards, leading to bodily harm.
