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Ivermectin and Mebendazole in Cancer: What Our New Review Found
Research · Cancer
Ivermectin and mebendazole are decades-old antiparasitic drugs now being studied in cancer research. A new review from the McCullough Foundation identified 37 anticancer mechanism classes across 25 cancer types in laboratory research, plus one 40-patient colorectal cancer trial. The authors say large randomized trials are the next step.
To see why two pills best known for fighting parasites ended up in an oncology review, it helps to start with a scoop of dirt.
A Scoop of Dirt
In 1974, a Japanese microbiologist named Satoshi Ōmura had an unusual routine. He and his team collected small soil samples wherever they went, on their daily commutes and on business trips.
One sample came from beside a golf course on the Izu Peninsula, about 100 kilometers southwest of Tokyo.
It turned out to be special. The soil held a bacterium no one had described before. Ōmura sent it to the drug company Merck, where a team, including William C. Campbell, turned the compound it produced into a medicine: ivermectin.
The drug launched in 1981 for livestock and pets. Within a few decades, more than 300 million people were taking it in a single year, mostly through free programs fighting river blindness. In 2015, the Nobel Committee honored Ōmura and Campbell with the Nobel Prize in Physiology or Medicine. (Not bad for a scoop of dirt from beside a golf course.)
Mebendazole's story is quieter. It has spent decades treating intestinal worms with little fanfare. (The two drugs work in different ways, and how mebendazole and ivermectin differ is worth knowing on its own.)
Neither drug was designed with cancer in mind.
Even so, laboratory studies have long suggested that both drugs may interfere with cancer cells in uexpected ways.* The catch is that the findings were scattered across the medical literature: a cell study here, an animal study there, a small human trial somewhere else.
So researchers, working with the McCullough Foundation, put the pieces on one table.
What the New Review of Ivermectin and Mebendazole Found
This resulted in a paper called "Combination Ivermectin and Mebendazole: A Comprehensive Review of Anticancer Mechanisms, Preclinical Activity, and Clinical Evidence as Adjunctive Treatment in Cancer Patients," which was posted as a 44-page preprint on Oct. 19, 2026. Its six authors include epidemiologist Nicolas Hulscher, MPH; Peter A. McCullough, MD, MPH; and Yale School of Public Health epidemiologist Harvey Risch, MD, PhD.
Hulscher described the goal this way:
"We examined published mechanistic, laboratory, and clinical evidence through October 2026, bringing together findings that had largely been investigated separately."
— Nicolas Hulscher, MPH, Epidemiologist, McCullough FoundationThe authors cataloged 29 distinct anticancer mechanisms for ivermectin and 26 for mebendazole. Some of them overlap. Combined, they form 37 distinct mechanism classes, and that evidence covers 25 human cancer types in preclinical research.*
"Preclinical" is the key word. It means cell cultures and animal models, not people. It's the first rung on a long ladder, and knowing which rung a finding sits on is the same skill behind judging whether a cancer supplement is safe and effective.
The authors summed it up:
"Together, ivermectin and mebendazole exhibit 37 distinct anticancer mechanism classes across 25 human malignancies, highlighting their exceptionally broad potential for therapeutic repurposing in oncology."
— Hulscher et al., Comprehensive Review (2026)Repurposing means taking a drug that's already approved and studying it for a new job. Both of these drugs are off-patent generics.
The Mebendazole Colorectal Cancer Trial That Stands Out
The human evidence is thinner, but it's also more interesting.
The review found six clinical studies that reported efficacy outcomes for ivermectin, mebendazole, or both. Three were positive, two were neutral, and one was an interim readout that couldn't be classified.
The standout is a randomized, double-masked, placebo-controlled trial that Hegazy and colleagues published in Life Sciences in 2022. All 40 patients had metastatic colorectal cancer, and all received standard treatment: the chemotherapy regimen FOLFOX4 plus bevacizumab. For 12 weeks, half of them also took mebendazole. The other half took a placebo.
| Outcome | Mebendazole + standard treatment | Placebo + standard treatment |
|---|---|---|
| Tumor response rate† | 65% (13 of 20) | 10% (2 of 20) |
| Median progression-free survival† | 9.25 months | 3 months |
Progression-free survival measures how long patients went before their cancer got worse. In this trial, that stretch was more than three times longer in the mebendazole group.
Did you catch the response numbers? That's 13 patients versus two.
The researchers also reported a significant drop in VEGF in the mebendazole group. VEGF is a protein involved in blood-vessel growth.
On safety, the review's authors wrote:
"Both are oral, widely available generic drugs that are well-tolerated alongside chemotherapy. No oncology trial of either agent has been stopped for toxicity."‡
— Hulscher et al., Comprehensive Review (2026)The Combination Gap Nobody Has Filled
Here's the strange part. Two well-known drugs and dozens of documented mechanisms exist. And yet:
"Despite extensive evidence for each drug individually, no published preclinical study has directly tested the ivermectin–mebendazole combination, leaving its potential synergy or antagonism unresolved."
— Nicolas Hulscher, MPH, Epidemiologist, McCullough FoundationSynergy would mean the two drugs work better together. Antagonism would mean they get in each other's way. For the ivermectin and mebendazole combination in cancer, nobody knows yet which it is.
The only human study of the two drugs taken together is a 197-patient observational cohort our medical team published earlier this year.§ An observational study watches what happens to patients. It doesn't assign treatments or compare them with a control group, so it's different from a randomized trial.
Turning Laboratory Promise Into Clinical Proof
The authors end with a clear request:
"Large, prospective, double-blind, parallel-group, randomized trials of combination ivermectin-mebendazole are urgently needed across a broad array of human malignancies."
— Hulscher et al., Comprehensive Review (2026)Hulscher went a step further: "We believe institutions such as the National Cancer Institute should immediately launch large randomized clinical trials."
We think that's the right ask.
A promising mechanism is a hypothesis. A 40-patient trial is a signal. Neither one is proof.
Could a medicine that started as a scoop of dirt earn a place in cancer care? Maybe. But that's a question for a trial, not a hunch.
The full review lists all 37 mechanism classes, all 25 cancer types, and every study behind these numbers, including the colorectal trial. You can read the full 44-page review on Zenodo.
Frequently Asked Questions About Ivermectin and Mebendazole in Cancer Research
Have ivermectin and mebendazole been tested together against cancer?
Not in a controlled study. The 2026 review found no published preclinical study that tested the combination directly. The only human study of the combination, a 197-patient observational cohort, was retracted by Anticancer Research in October 2026, and the review's authors are calling for large randomized trials.
What does "preclinical" mean in cancer research?
Preclinical research uses cell cultures and animal models rather than people. It helps scientists identify possible mechanisms, but results in the lab do not always carry over to patients. That is why clinical trials are the next step.
Are ivermectin and mebendazole approved to treat cancer?
No. Neither ivermectin nor mebendazole is FDA-approved to treat cancer. Both are approved antiparasitic medicines, and their possible role in cancer care is still being studied. Talk with your oncologist before making any change to cancer treatment.
Key Takeaway
In the lab, ivermectin and mebendazole have built a broad case: 37 anticancer mechanism classes across 25 cancer types. In people, the strongest evidence so far is one 40-patient colorectal cancer trial. That's a signal worth testing, which is why the review's authors are calling for large randomized trials of the combination.
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References
- Hegazy, S. K., El-Azab, G. A., Zakaria, F., Mostafa, M. F., et al. (2022). Mebendazole; from an anti-parasitic drug to a promising candidate for drug repurposing in colorectal cancer. Life Sciences, 299, 120536. https://doi.org/10.1016/j.lfs.2022.120536 (Editor's note: the fifth author's name could not be confirmed.)
- Hulscher, N. (2026, October 20). BREAKING: The most comprehensive ivermectin–mebendazole cancer paper to date finds 37 distinct anticancer mechanisms across 25 human cancer types. Focal Points. https://www.thefocalpoints.com/p/breaking-the-most-comprehensive-ivermectinmebend
- Hulscher, N., Thorp, J. A., Victory, K., Gillooly, P., McCullough, P. A., & Risch, H. (2026). Combination ivermectin and mebendazole: A comprehensive review of anticancer mechanisms, preclinical activity, and clinical evidence as adjunctive treatment in cancer patients (Version 1) [Preprint]. Zenodo. https://doi.org/10.5281/zenodo.23475387
- Hulscher, N., Victory, K., Thorp, J. A., Pinsky, D., Diaz-Villalobos, A., Gillooly, P., Coulson, F., Annazone, M., Radesi, C., Brooks, J., McCullough, P. A., & Risch, H. (2026). Real-world clinical outcomes of ivermectin and mebendazole in cancer patients: Results from a prospective observational cohort. Anticancer Research, 46(6), 3243–3255. https://doi.org/10.21873/anticanres.18194 (Retraction published 2026, Anticancer Research, 46(10), 5877)
- Nippon.com. (2015, October 13). The Nobel discovery protecting 300 million people from the risk of blindness. https://www.nippon.com/en/column/g00321/
- The Nobel Assembly at Karolinska Institutet. (2015, October 5). The Nobel Prize in Physiology or Medicine 2015 [Press release]. NobelPrize.org. https://www.nobelprize.org/prizes/medicine/2015/press-release/
* Preclinical (laboratory and animal) findings do not establish effects in people.
† This was a small trial (20 patients per arm) and was registered after it started (NCT03925662). The results have not been independently replicated, and no overall-survival benefit was reported.
‡ This is the review authors' statement. Neither ivermectin nor mebendazole is FDA-approved to treat cancer.
§ Hulscher et al. (2026), published in Anticancer Research, received an Expression of Concern in June 2026 and was retracted in October 2026. The editor cited methodological and analytical problems, alleged no misconduct, and the authors dispute the retraction.
The review's authors are affiliated with The Wellness Company and/or the McCullough Foundation. The review is a preprint and has not yet been peer-reviewed.
Medical disclaimer: This content is for informational purposes only. It is not medical advice and does not replace consultation with a qualified healthcare professional. Talk with your oncologist before making any change to cancer treatment.
