Ivermectin and Mebendazole in Oncology
A plain-language guide to a review of how decades-old anti-parasitic medicines behave against cancer in the lab, and what the human evidence shows.
Summary of: “Combination Ivermectin and Mebendazole: A Comprehensive Review of Anticancer Mechanisms, Preclinical Activity, and Clinical Evidence as Adjunctive Treatment in Cancer Patients.” Hulscher N, Thorp JA, Victory K, Gillooly P, McCullough PA, Risch H. Manuscript draft, literature searched through October 2026.
DOI 10.5281/zenodo.23475387
From lab promise to proof in people
The one placebo-controlled trial: colorectal cancer, mebendazole only.
Our call is for proper randomized trials, and soon.
The short version - This review is the 1st to put both drugs side-by-side.
Ivermectin and mebendazole are inexpensive, oral medicines used for decades to treat parasitic worm infections. Both are on the World Health Organization’s list of essential medicines. Over the years, lab researchers have published many studies suggesting each one can also damage cancer cells. Together, ivermectin and Mebendazole exhibit 37 distinct anticancer mechanisms across 25 human malignancies.
Resistance and Dissemination
How cancers survive treatment and spread. Both drugs target hard-to-kill cancer stem cells and the pumps that push chemotherapy back out of cells, and both slow the growth of new blood vessels. In mice, ivermectin reduced spread to the lungs.
- Blocks drug-resistance pumps
- Reduces cancer stem-cell populations
- Suppresses new blood vessel growth
- Sensitizes tumors to chemotherapy
- Blocks a neutrophil route to spread
- Reduces invasion and metastasis
- Ivermectin
- Mebendazole
- Both
Lab and animal findings. Source: Figure 2, Tables 1 and 3.
It counts 29 cancer-fighting mechanisms for ivermectin and 26 for mebendazole. Grouping the overlaps gives 37 distinct mechanisms between them.
In lab and animal studies, ivermectin showed activity in 20 human cancers (plus one dog cancer) and mebendazole in 17. Together that covers 25 human cancer types.
The two drugs mostly work in different ways, which is why the authors think they could complement each other. But nobody has yet tested them together in the lab.
Human evidence is thin: six studies reported whether patients did better. Three were positive, two were neutral, and one is still in progress.
Response rate when mebendazole was added to standard chemotherapy for advanced colorectal cancer, in a 40-patient placebo-controlled trial.
Why look at old drugs for cancer?
Developing a brand-new cancer drug takes many years and costs a great deal. “Repurposing” means testing a medicine that is already approved for something else. Because its safety and how the body handles it are already known, much of the early work can be skipped.
The authors note three gaps this review set out to fill. No one had compared the two drugs’ mechanisms side by side, even though people already take them together outside of trials. Earlier reviews focused on lab science more than human data. And a lot of research published between 2021 and 2026 had not yet been pulled together.
The authors argue both drugs score unusually well. Several of these points are tested, and qualified, later in the review.
How the review was done
Sources searched
PubMed, Europe PMC and Google Scholar through October 2026, plus ClinicalTrials.gov, cancer conference abstracts and reference lists of earlier reviews.
What was included
Peer-reviewed lab, animal and human studies of either drug in cancer.
What was left out
Fenbendazole, a veterinary relative that isn’t approved for people. Also excluded were collections of patient testimonials from social media and self-published websites.
How mechanisms were counted
By the specific target in the cell, not by the end result. “The cell died” is not counted separately from the thing that killed it.
How human studies were graded
Positive if tumors shrank or patients lived longer without progression; neutral if no benefit was shown. Safety-only trials and single-patient case reports were set aside.
How each drug acts on cancer cells in the lab
The review lists 29 mechanisms for ivermectin in seven families, and 26 mechanisms for mebendazole in eight. In everyday terms:
Source: Abstract, Tables 1 and 3.
Switches off several “grow and divide” signals (WNT, PAK1, Akt/mTOR, YAP1). It also stiffens the cell’s internal scaffolding so the cell can’t split.
Blocks the “doorway” proteins (importins) that carry growth and survival instructions into the cell’s control center.
Interferes with proteins that turn cancer-driving genes on, and with the cell’s DNA-repair kit.
Disables heat-shock proteins that help stressed cancer cells survive.
Disturbs the cell’s electrical balance and triggers a form of cell death that alerts the immune system. In mice this made an immunotherapy drug work where neither worked alone.
Damages energy production and creates harmful oxidative stress. Cancer cells, which rely heavily on their mitochondria, are hit harder than normal cells.
Targets hard-to-kill cancer stem cells, blocks the pumps that push chemotherapy out of cells, and in mice reduced spread to the lungs.
Dissolves the cell’s internal scaffolding so it gets stuck mid-division and dies. This was first shown in lung cancer cells in 2002.
Disables proteins that keep cancer cells from dying (Bcl-2, XIAP) and activates the cell’s built-in suicide program.
Blocks VEGFR2, a signal tumors use to grow new blood vessels.
Inhibits several growth enzymes (BRAF, MEK, MAPK14 and others) and the hedgehog pathway that drives some childhood brain tumors.
Shuts down cancer-driving genes like MYC and MYB and reduces how much sugar cancer cells can burn.
Reduces the enzymes and signals cancer cells use to invade nearby tissue.
Pushes immune cells called macrophages into “attack” mode and boosts natural killer cells.
Makes tumor cells more sensitive to radiation and to several chemotherapy drugs.
All of this comes from cells in dishes and from animals. One of the liver-cancer papers the review cites for ivermectin was later retracted over duplicated images. In a 2026 rat study, a nasal-spray nanocapsule form of ivermectin shrank brain tumors more than plain ivermectin did.
In head and neck cancer, mebendazole worked well in dishes, but tumors in treated mice were slightly larger than in untreated mice (though less actively growing). The authors call this the clearest mismatch between lab-dish and animal results for either drug.
Where the two drugs’ cancer lists overlap
Ivermectin showed activity in 20 human cancers plus a dog breast tumor; mebendazole in 17, with brain tumors especially well represented because it can reach the brain. Across the 25 human cancers, both drugs showed lab activity in 12, ivermectin alone in 8 and mebendazole alone in 5.
Lab and animal evidence only. Effectiveness in patients is not established for either drug. Source: Tables 2 and 4, Figure 1.
Why the authors think they could work together
Our Observational Study of Ivermectin and Mebendazole in Cancer Care has studied this combination.
It is the first study to report on patients taking ivermectin and mebendazole together. Controlled lab, animal and randomized studies of the pair are the next step.
What happened when people took them
The one placebo-controlled trial
Forty people with colorectal cancer that had spread were given standard chemotherapy (bevacizumab plus FOLFOX4). Half also took mebendazole 500 mg twice a day for 12 weeks; half took a placebo. Neither patients nor doctors knew who got which.
Mebendazole was well tolerated. However, the trial was small and run at a single center, and there was no significant difference in one-year survival. With 20 patients per group it was too small to answer that question either way.
Early-phase trials
Most early trials tested mebendazole in brain tumors, alongside chemotherapy. They mainly showed it could be given safely at high doses (up to 200 mg/kg in adults and children). In the main efficacy trial, 88 people with recurrent glioblastoma were randomly given one of two mebendazole combinations. Neither group reached the survival goal the researchers had set in advance.
- Advanced digestive cancers (11 patients): only 5 reached the target blood level even at 4 g a day. All patients’ cancers progressed, and the study stopped early.
- METRICS study (95 glioblastoma patients): mebendazole was given with metformin, atorvastatin and doxycycline. Median survival was 26.3 months vs. about 15 months historically. The four drugs’ effects can’t be separated, and the journal issued an expression of concern in 2023 that is still unresolved.
- Ivermectin in triple-negative breast cancer: an ongoing trial at Cedars-Sinai is pairing ivermectin with immunotherapy. Interim results in heavily pretreated patients: median 2.5 months before progression, with 37.5% benefiting at 4 months. There is no comparison group and final results are pending.
- ICONIC trial: an 80-patient randomized trial of ivermectin doses with immunotherapy. It is registered and began enrolling in 2026, with no results yet.
The striped bar is a post hoc subgroup (patients in better general health), chosen after the results were known. Serious side effects (grade 3–5): 18.6% with temozolomide, 9.5% with lomustine. Source: §9.2, refs. 122–123.
Observational data and case reports
Two single-patient reports describe striking responses to mebendazole alone. One man with adrenal cancer stayed stable for 19 months. Another man’s colon cancer metastases nearly disappeared in six weeks. Single cases can’t prove the drug caused the improvement.
The Research They Don’t Want You to Read
The only human data on the two drugs used together comes from the authors’ own survey study. Patients prescribed a combined capsule (25 mg ivermectin + 250 mg mebendazole) through a U.S. telemedicine service reported their own outcomes. Anticancer Research published it in June 2026 and retracted it on October 1, 2026. It was peer reviewed, published, then retracted.
The review’s authors dispute the retraction. They argue the study’s limits were openly stated and that a correction should have been enough. Any figures shown are as reported, for transparency. They are not evidence that the drugs work.
No errors were found. The data didn’t change.
Read it and decide for yourself.
- The Wellness Company Chief Medical BoardDespite passing a rigorous three-month peer review, the journal unilaterally retracted this study after publication, citing complaints from unnamed members of the ‘international medical community,’ while admitting there were no errors in the methodology or results.
This is a primary example of medical censorship used to hide evidence that low-cost repurposed drugs have the potential to treat medical conditions like cancer.”
The study’s headline 84.4% “clinical benefit” adds together the first three. 38.1% of patients did not complete follow-up. Many were also having chemotherapy (27.9%), radiation (21.3%) or surgery (19.7%). Source: §9.3, ref. 133.
Most common: stomach and bowel (38.7% of those affected), tiredness (32.3%), dizziness (22.6%). Side effects rose with dose; reported outcomes did not. Source: §9.5.
Where the research is headed
The question is being studied elsewhere with public money. The U.S. National Cancer Institute confirmed in early 2026 that it had begun lab work on ivermectin. Florida’s Cancer Innovation Fund directed about $3.39 million to three ivermectin projects in 2025–26. None of them tests ivermectin together with mebendazole.
Source: §9.3, refs. 139–141.
Reports of harm from self-treatment
Three published cases describe people with cancer harmed after taking these drugs without medical supervision:
A woman with breast cancer developed encephalopathy after three weeks of an ivermectin liquid of unknown strength. She recovered after stopping it.
A child with cancer developed ivermectin toxicity. The case authors blamed podcast and social-media claims that it cures cancer.
A 65-year-old man with prostate cancer, after three months of veterinary fenbendazole and ivermectin taken on the advice of online support groups.
At one U.S. cancer center, 499 of 297,223 patients said they were taking ivermectin on their own, at 154 different dosing schedules.
Taking them alongside cancer treatment
Mebendazole has been given with chemotherapy or targeted drugs in five trials without new safety problems. For ivermectin, a pooled analysis found 36 cancer patients who received it for a parasite infection (or COVID-19), several during chemotherapy. None had a serious side effect blamed on ivermectin. Those patients weren’t taking it for cancer, so this says nothing about whether it works.
Two decades of research, at a glance
Mebendazole shown to break down scaffolding in lung cancer cells
Ivermectin’s discovery wins the Nobel Prize in Medicine
METRICS glioblastoma study reports
Digestive-cancer, glioblastoma and colorectal trials report
Expression of concern issued on METRICS
Podcast-linked co-prescribing jump; Florida funds three ivermectin projects
NCI lab work, ASCO statement, ICONIC trial begins enrolling
Combination cohort retracted; literature search closes
The evidence scorecard
The authors stress that no study showed either drug making outcomes worse. They also note that neither neutral study had a no-drug comparison group that could have detected harm. Only one positive study was randomized and placebo-controlled. The review counts the retracted cohort as positive, but this summary labels it retracted.
What the evidence can’t tell us yet
In 2026 the American Society of Clinical Oncology (ASCO) stated that no robust peer-reviewed evidence shows ivermectin or fenbendazole to be safe or effective for any cancer. It cautioned against using them outside well-designed clinical trials. Mebendazole was not named. The review’s authors argue this blanket advice is more restrictive than the evidence warrants, particularly for studying the drugs as add-ons to standard treatment.
The dose gap. Many lab effects need higher drug concentrations than standard doses produce in the blood. The authors point to some mechanisms that work at much lower levels, but this remains the most common objection.
Uneven lab science. Several mechanisms rest on a single study that nobody has repeated. Some are computer-modeling studies rather than real experiments. Negative results tend to go unpublished.
Thin human evidence. In the authors’ words, the human studies so far “do not constitute an evidence base adequate to support clinical use outside a trial.”
Unpredictable absorption. In one trial, 6 of 11 patients never reached the target mebendazole level, even at the maximum daily dose.
Real harm from self-treatment. Brain toxicity, toxicity in a child and severe liver injury have all been reported.
What the authors want to see next
Their case for urgency: both drugs are off-patent, cost-effective, and already have known safety profiles. Because no company stands to profit, few trials have been funded. Meanwhile people are already taking the drugs on their own.
Dashed line = 1.0, no change. “Mebendazole-type drug” = any benzimidazole prescribed the same day. Source: §12, ref. 150.
The proposed research steps, in the order the authors give them
Test the combination in the lab first
Including whether the drugs cancel each other out, before any further use in people.
Run a properly sized randomized trial
Placebo-controlled, in one defined cancer, using the colorectal result to plan its size.
Pick patients by biomarkers
That lab work suggests predict response, such as YAP1 in stomach cancer or hedgehog activity for mebendazole.
Improve formulations
The right mebendazole crystal form or nanocapsules for ivermectin, and measure blood levels during trials.
Consider trials in pet dogs
With brain tumors, which resemble the human disease and could give faster, cheaper answers.
The bottom line
In lab studies, ivermectin and mebendazole attack cancer in a remarkably wide range of ways, and mostly in different ways from each other. Both are cheap, oral and have long safety records. One small placebo-controlled trial of mebendazole was encouraging.
Against that, there are only six human studies of effectiveness, one of them placebo-controlled. No lab study has tested the two drugs together. The authors conclude that neither drug can be called an established cancer treatment today, and that well-designed trials are the way to settle the question.
Don’t start, stop or change any cancer treatment based on this research.
Both drugs interact with other medicines and have caused serious harm when taken without supervision. Talk with your provider or oncologist, and ask whether a clinical trial might be right for you.
Disclosures from the manuscript: All authors are affiliated with and/or receive salary support from The Wellness Company (TWC). No external funding. AI tools (ChatGPT) were used to help create the manuscript’s figures.
About this page: Plain-language summary of an unpublished review manuscript, written for general readers. The charts redraw numbers reported in the manuscript and have not been independently verified. This page is for information only and is not medical advice.