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William Supple, PhD, is a retired neuroscientist and the author of Cancer Is a Parasite (Skyhorse Publishing). His Substack, fenbendazole.substack.com, has approximately 3 million readers, making it one of the largest, if not the largest, on the platform. He accepts no paid subscriptions or compensation of any kind. The following reconstructs his account from our interview. Any errors or misinterpretations are mine.
Summary
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Fenbendazole, a dog dewormer costing pennies per dose, kills cancer cells through 11 simultaneous mechanisms, targets cancer stem cells that chemotherapy leaves intact, and has no meaningful side effects outside a single interaction with acetaminophen.
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A 1976 paper named the molecule “oncodazole” because researchers who studied it understood exactly what it did to cancer cells. That paper was physically removed from accessible library stacks for decades. The cancer treatment industry built itself into a trillion-dollar enterprise in the space that suppression created.
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Countries with national antiparasitic drug programs show cancer rates half those of countries without them. India’s rate is one-third that of the United States. Israel, the one Middle Eastern country without a mass deworming program, has twice the cancer rate of its geographic neighbors.
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Supple’s mother-in-law was discharged from the hospital after receiving last rites, with metastatic breast cancer throughout her bones, lungs, and liver. She took 222 mg of fenbendazole daily in yogurt without knowing it. Her tumor markers normalized in 3 months. She’s 88 and cancer-free.
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Cancer and parasites share aneuploidy, independent circadian rhythms, molecular mimicry, and microtubule vulnerability. The same drug kills both. Supple argues this is not coincidence but identity: cancer behaves as a parasite and should be studied and treated as one.
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Take 222 mg daily with fat. Don’t take it with acetaminophen (Tylenol). (Don’t ever take that! See 320. TYLENOL IS A PHARMA ATROCITY, AND ASPIRIN IS A SUPPRESSED WONDER DRUG.
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Pregnant women should avoid it. If you monitor liver enzymes in the first 8 weeks, which is unnecessary, a transient rise signals die-off, not toxicity.
How a neuroscientist ended up here
Supple spent his career studying brainstem mechanisms of learning and memory at Dartmouth and the University of Vermont, with about 40 published papers on cerebellar function. He’s not an oncologist. He got pulled into cancer research in 2021 when his mother-in-law was discharged from a Florida hospital after receiving last rites.
She was 83, and imaging taken for what seemed like a bowel obstruction had found metastatic cancer in her bones, lungs, and liver. It was metastatic breast cancer, a decade after a bilateral mastectomy, which Supple believes was seeded into her bloodstream when surgeons cut through tumor tissue in 2009. Her immune system kept it dormant. Two Moderna COVID shots in the spring and summer of 2021 coincided with its explosive reactivation. This is what the community now calls turbo cancer: dormant cells, suddenly released from immune suppression, producing disease at terrifying speed.
She refused chemotherapy and radiation. The hospital wasn’t sure she’d survive the two-mile drive home.
In the weeks that followed, Supple came across a single comment on an unrelated Substack post: “fenbendazole cured my prostate cancer.” That sentence sent him down a rabbit hole that consumed the next four years and produced Cancer Is a Parasite, published by Skyhorse in 2025.
What fenbendazole is and why fat matters
Fenbendazole is a veterinary antiparasitic that has dewormed dogs for decades. It’s available at FenbenLabs.com, on Amazon, and at Tractor Supply. The standard dose is 222 mg, which is the dose for a 10-pound dog. That number entered the human cancer community by accident and stuck. There are no dose-escalation studies in humans. What exists is a large and growing record of people using 222 mg/day, clearing cancer, and reporting no side effects.
The human pharmaceutical relative is mebendazole (Vermox), roughly 600 times more expensive and designed to stay in the gut, which makes it effective for intestinal parasites but limits its reach to solid tumors. Fenbendazole is more fat-soluble, enters systemic circulation more readily, and reaches cancers throughout the body. Albendazole is another close relative. For anti-cancer purposes they’re functionally interchangeable.
Fat co-administration is not optional. Fenbendazole is hydrophobic; swallowing it with water produces poor absorption. Supple’s family takes it sprinkled on heavily buttered toast. His mother-in-law took it in yogurt. An organic chemist in his Substack community confirmed that fenbendazole, as a carbon-14 molecule, binds well to lipids. Take it with fat, every time.
One absolute contraindication: don’t combine fenbendazole with acetaminophen (Tylenol). Mouse data suggests the combination causes liver problems. Tylenol is a documented liver toxin with no legitimate therapeutic use. Beyond that single interaction, fenbendazole has no known clinically significant drug interactions.
How it kills cancer: 11 mechanisms, no survivors
The primary mechanism is microtubule depolymerization. Microtubules are the internal scaffolding cells use to divide, expel waste, absorb nutrients, and maintain their architecture. Fenbendazole dissolves that scaffolding inside cancer cells while leaving healthy human cells intact. Without microtubules, the cancer cell can’t divide, can’t move nutrients in or waste out, and collapses.
Standard chemotherapy also targets microtubules, but through stabilization rather than dissolution, and through a single pathway. Cells vulnerable to that one mechanism die. Cells that aren’t vulnerable survive, pre-selected for resistance. The tumor that comes back is harder to kill than the one that was treated. This is multi-drug resistance, and it’s why chemotherapy rarely cures late-stage cancer. It buys time. The cancer it leaves behind is worse.
Fenbendazole doesn’t leave survivors. Beyond microtubule disruption, it blocks tumor angiogenesis, cuts off the cancer’s glucose supply by disrupting the Warburg effect, prevents molecular mimicry (the trick cancer cells use to evade immune detection), blocks P-glycoprotein efflux pumps (the cell’s toxin-flushing system), halts cell migration, restores the p53 tumor suppressor gene, and kills cancer stem cells.
That last item deserves emphasis. Cancer stem cells are the roots of recurrence. Chemotherapy kills the bulk of a tumor and produces remission. The stem cells survive. The tumor they rebuild is descended entirely from drug-resistant stock. Oncologists have no answer for this. Fenbendazole kills cancer stem cells, which is why it rescues patients who have already exhausted standard treatment.
The oncodazole suppression
In 2002, researchers at MD Anderson and the University of Texas published a paper in a major oncology journal claiming to demonstrate, for the first time, that a drug of this class had anti-cancer capabilities. Supple read that paper after immersing himself in the literature, then went back and found a 1976 paper by a different research group that had made the same observation.
The 1976 researchers had been so impressed by what the molecule did to cancer cells that they named it. They called it oncodazole.
By 1984, a different paper on the same molecule had dropped the name oncodazole and renamed it nocodazole, without explanation and without citing the 1976 paper. The 2002 paper claiming primacy didn’t cite it either. Not one reviewer at a major oncology journal recognized a discovery that had already been made and named 26 years earlier.
The explanation is not that oncologists are stupid. In the pre-internet era, a paper that wasn’t in the physical stacks at a major research library effectively didn’t exist. The oncodazole paper was removed from accessible circulation. When journals began digitizing their archives in the early 2000s, it came back as a scanned PDF image rather than indexed searchable text, which is why it remains hard to find today. Supple found it by accident. He paid $125 for the copyright to preserve a documented paper trail.
In 2025, after his book’s publication, someone sent him a CIA document released under the Freedom of Information Act in 2016. The document, dated 1951, described a CIA assessment that the Soviet Union had determined in the 1930s that antiparasitic drugs cured cancer.
The Soviets knew in the 1930s. The CIA knew in the 1950s. American researchers knew in 1976 and named the molecule for what it did. The chemotherapy drugs that made Big Pharma what it is, the Vinca Alkaloids and the Taxanes, operate in the same biological space as fenbendazole. They’re mechanistic knockoffs, doing the same thing sloppily, incompletely, and with catastrophic side effects. The patients who could have been saved in the decades between 1976 and now died of cancer or of the treatments designed to replace a cheap, available, safe cure with expensive ones.
The epidemiology
The World Health Organization (WHO) collects cancer incidence by country. India’s rate is 93 cases per 100,000 people per year. The United States’ rate is 333. India runs a national deworming program, administering antiparasitic drugs to the population on February 10th and August 10th every year. The US has nothing comparable.
Supple extended the analysis using WHO data for the entire world. Countries with mass drug administration programs for antiparasitic agents show cancer rates half those of countries without such programs. The 123-plus deworming nations differ from each other in genetics, diet, geography, and every other measurable variable. The one thing they share is antiparasitic drug use. Half the cancer rate.
The most striking data point comes from the Middle East and North Africa, a region of roughly 23 countries with broadly similar climates, diets, and genetic backgrounds. One country in that group has no mass deworming program: Israel. Israel’s cancer rate is twice the regional average.
No career epidemiologist who looks at this data and declines to publish a paper on it is making a simple oversight. The data is not subtle.
We all have parasites
Americans have been told they don’t carry parasitic infections. This is a lie, and not a well-intentioned one.
Parasites arrive through food, soil, and pets. If you have a dog, you’re almost certainly infected. The same parasites that cycle through dogs cycle through the humans who kiss them, let them lick their faces, and sleep in the same bed. We deworm our dogs twice a year. We don’t deworm ourselves at all. Sushi, undercooked meat, and organic vegetables grown in soil where animals defecate are all transmission routes. Adult parasites can be killed; their eggs are everywhere and survive.
Parasites persist by making themselves invisible, modulating the immune response to their presence and dialing down the alarm so they can remain without triggering full-scale attack. The result is subclinical, chronic, low-grade inflammation. Inflammation drives cancer. A sustained parasitic infection producing constant inflammation that the host never detects is a sustained, unrecognized cancer risk factor.
Two mechanisms, one cheap intervention, half the cancer rate. First, antiparasitic drugs directly kill incipient cancer cells by targeting the microtubule vulnerability they share with parasites. Second, antiparasitic drugs eliminate the chronic parasitic inflammation that is a primary unrecognized driver of malignancy. The answer has sat in a 50-pound bag at Tractor Supply for less than the cost of a cup of coffee per dose.
Cancer is a parasite
Supple’s book argues that cancer doesn’t merely share vulnerabilities with parasites. It is one, or at minimum behaves so identically that treating them as distinct categories has cost science a century of understanding.
The pharmacological evidence is the starting point: the same drug kills both through the same mechanism. If one intervention clears two diseases, there’s a shared biological substrate, not a coincidence.
Parasites and cancer cells are the only two cell types in the body that exhibit aneuploidy: a disorganized, chaotic karyotype in which chromosomes are mismatched, fragmented, or duplicated in bizarre ways. Normal cells carry 23 matched chromosome pairs. A normal karyotype looks orderly. A parasite’s karyotype, and a cancer cell’s, looks like a junk drawer of chromosomal fragments. Both need to evolve rapidly within the lifespan of a single host organism, adapting to whatever defenses the host deploys. The disorganized extra genetic material is their toolkit for rapid adaptation.
Both also develop biological clocks not synchronized to the host’s circadian rhythms. Normal cells are entrained to the host’s clock. As tumors mature, cancer cells develop their own rhythms. Parasites do the same thing. A cancer cell that starts as a rogue host cell and ends up on its own biological clock has transitioned into something effectively non-self, an independent biological entity that has broken from the host’s regulatory systems. That is precisely what a parasite is.
Both exploit molecular mimicry to evade the immune system, disguising themselves as normal tissue. This is the biological basis of the immune checkpoint inhibitors like Keytruda that have attracted billions in investment. Fenbendazole disrupts molecular mimicry directly, without the cost or the side effects of immunotherapy.
The practical implication is that we can study parasites to understand cancer. They’re in a dish. There are no ethical constraints on what researchers do to them. Our knowledge of parasite biology is far more advanced than our knowledge of cancer biology. If the two are expressions of the same phenomenon, that gap can be closed. Parasitologists and oncologists have never been in the same room. They need to be.
His mother-in-law’s recovery
His wife was in Florida with her mother when Supple started sending fenbendazole. Before giving it to her mother, his wife took it herself, reasoning that a 50% genetic match was a reasonable safety screen. No side effects. Her father mixed it into her mother’s yogurt every day. 222 milligrams. She didn’t know she was taking anything. No placebo effect, no expectation, no psychology.
Within 2 weeks, she began to rally. She started eating. Her appearance, activity, and demeanor changed visibly. At 4 weeks, she discharged hospice. At 8 weeks, she returned to her oncologist.
Her CA27-29 tumor marker, which measures metastatic breast cancer burden, had been 316 when she left the hospital. Under 100 is metastatic; under 38 is normal. It had fallen to 131. The oncologist had expected never to see her again. He told her: keep doing whatever you’re doing.
She continued. The spinal cord lesions that required targeted radiation resolved faster than the radiologist expected, consistent with published data showing fenbendazole potentiates radiation. By 3 months, all tumor markers were normal. She’s been cancer-free since. She celebrated her 88th birthday.
That result, a woman given last rites who walked out of hospice and cleared stage-IV metastatic breast cancer in 3 months, is why Supple launched a Substack. He now has approximately 3 million readers, the largest fenbendazole community in existence, and charges nothing.
The liver enzyme question
A paper warning about fenbendazole and liver damage appears first on most search results for the topic. Search ranking at that scale doesn’t happen by accident when money is at stake.
Supple tracked his mother-in-law’s alanine aminotransferase (ALT) and aspartate aminotransferase (AST) alongside her tumor markers throughout treatment. When she started fenbendazole, her liver enzymes were normal. As her tumor markers dropped sharply over the first 2 months, her liver enzymes rose to around 150 for both, well above the normal ceiling of roughly 30. Then, while she continued taking fenbendazole, they returned to normal and stayed there.
If the drug were hepatotoxic, the enzymes would have stayed elevated for as long as she took it. They didn’t. The transient spike coincided precisely with the active cancer-killing phase and resolved without stopping the drug. The most likely explanation: as fenbendazole killed billions of cancer cells, their cellular debris flooded the bloodstream and passed through the liver for processing. The liver was working hard. It wasn’t being poisoned.
A transient ALT and AST rise in the first weeks of fenbendazole treatment is probably a good sign. The liver is clearing the dead. Oncologists who have never used a drug that actually clears all the cancer have no framework for interpreting what that looks like in the labs. Supple now does.
Dosing
For cancer treatment, 222 mg/day continuously with fat is the protocol with the most case report support. The 3-days-on/4-days-off schedule that circulates in the community has no pharmacological basis Supple is aware of; the continuous daily dose worked in his mother-in-law’s case and in the majority of his 22 documented case reports.
For cancer prevention, Supple and his wife take 222 mg/day for 3 consecutive days once every 3 months, which exceeds India’s twice-yearly national program. That twice-yearly program, if the WHO data is right, cuts cancer incidence in half.
Don’t take it with Tylenol. Pregnant women should avoid it. Monitor liver enzymes at 4 and 8 weeks; a transient rise is expected and indicates activity, not damage.
A note from the author
I’m a 72-year-old physician with Parkinson’s disease, confirmed Lyme disease from a tick-borne infection I missed for years, documented heavy metal burden, and gut dysbiosis. I’ve been taking 222 mg of fenbendazole daily with fat since starting my current treatment protocol, which also includes chlorine dioxide and methylene blue.
Supple’s epidemiological case is the most persuasive I’ve encountered for routine antiparasitic use in a Western population. He says that chronic low-grade parasitic inflammation is an unrecognized driver of cancer and neurodegeneration, which fits my own clinical picture with uncomfortable precision. The same vectors that gave me Borrelia miyamotoi carry other passengers. The gut dysbiosis that has resisted months of restoration efforts is exactly what a parasite-driven chronic inflammatory state produces.
The oncodazole story is the one that should end careers. In 1976, researchers watched this molecule annihilate cancer cells and named it for what it did, but the paper was buried. The chemotherapy industry that rose in its absence costs American patients hundreds of billions of dollars a year and produces survival curves that haven’t meaningfully improved in decades. The answer was in a 50-pound bag at a farm supply store the entire time.
If you have cancer, take fenbendazole. If you know someone with cancer, send them this post. If your oncologist threatens to drop you for asking about it, ghost them.
Synthesis
The suppression of fenbendazole as a cancer treatment is not a conspiracy theory. It’s a documented sequence of events: a molecule named for its cancer-killing properties in 1976, a paper physically removed from accessible library stacks, a CIA assessment in 1951 that the Soviets had already reached the same conclusion, and a trillion-dollar chemotherapy industry built in the space that suppression created. The Vinca Alkaloids and Taxanes that define modern oncology are mechanistic knockoffs operating in the same biological territory as fenbendazole, doing it incompletely and lethally.
What Supple adds that goes beyond the fenbendazole community’s existing case-report evidence is an epidemiological argument that demands a response from mainstream medicine. Half the cancer rate in countries that deworm. One-third the cancer rate in India. Twice the cancer rate in the one Middle Eastern country that doesn’t deworm. This is not a signal buried in confounded data. It screams.
The implications extend beyond cancer. If chronic, subclinical parasitic infection is a primary unrecognized driver of the inflammatory substrate that produces malignancy, it is almost certainly also contributing to neurodegeneration, autoimmune disease, and the metabolic disorders that define Western morbidity. The American medical system doesn’t look for parasites because it decided they aren’t there. That decision has never been examined. It should be.
Fenbendazole is pennies per dose, universally available, and has a safety profile that few supplements match. The only reason not to take it is that no one told you to. Consider yourself told.
Selected references
1. William Supple’s Substack: fenbendazole.substack.com
2. Cancer Is a Parasite by William Supple (Skyhorse Publishing, 2025) — Amazon
3. FenbenLabs.com — pharmaceutical-grade fenbendazole supplier
5. WHO Global Cancer Observatory: cancer incidence by country
6. Dogris N. et al. on fenbendazole and microtubule disruption in cancer cells — PubMed
7. 320. Tylenol Is a Pharma Atrocity, and Aspirin Is a Suppressed Wonder Drug — Robert Yoho, MD
8.FLCCC Alliance: Fenbendazole in post-vaccine injury protocols
Hot off the press from Mr. Supple’s Substack:
This past week saw a firestorm of controversy and revelation regarding the anticancer actions of antiparasitics. First, the publication of my book, Cancer is a Parasite, showed readers that cancer cells behave in just about all respects, just like parasites, with the most practical takeaway being that the antiparasitic fenbendazole kills both parasites and cancer. Cancer is a Parasite shows that antiparasitics like fenbendazole are legitimate cures for many cancers, and my book proves that statement on the molecular, mechanistic, biochemical, genetic, preclinical, clinical (human self-treatment), epidemiological, and theoretical (epistemological) levels.
Cancer is a Parasite proves unequivocally with the published scientific record that pharma knew fenbendazole cured cancer in the 1970s, actively covered it up, and repurposed its mechanism into “standard of care” oncology drugs.
Second, these revelations gave meaning and context to a previously unappreciated CIA memo from 1951, declassified in 2014. In it a CIA analyst writes that Soviet scientists in the 1930s noted the striking similarities between parasitic worms and cancerous tumors. They both thrived under similar metabolic conditions, surviving in low-oxygen environments and storing large glycogen reserves. The memo also described how the Soviets found that anti-parasitic drugs killed both the parasites and cancer cells. Which is exactly what this Substack is all about, starting with my mother-in-law self-treating her metastatic breast cancer with fenbendazole in 2021 and now getting ready to celebrate her 88th birthday next month.
Yoho note: Act now by clicking the link in the title above to be the three millionth and first subscriber.
Parting Shot #1 from Bill Supple
Hi Bob,
One topic I forgot is the use of fenbendazole for non-malignant growths, such as desmoid tumors and skin lesions. Topical application of 10% fenbendazole cream (available on Amazon or mixed into a skin cream) eradicates basal and squamous cell lesions. I personally use it on SCC. Place a dab of the cream on the spot, and cover with a bandaid. Replace the cream and band-aid every day for about 28 days. The lesion will turn red, dry up, flake off, and new skin will appear. No more cutting or Mohs surgery!
Best wishes,
Bill
PS, trying fenbendazole for your Lyme infection might be worth a shot. Low risk/ potentially high reward.
I wrote him back that I’m now buttering my toast with 222 mg daily.
Parting Shot #2 from an AI: Does fenbendazole have any effect on Lyme disease?
The short answer: there’s theoretical plausibility and substantial anecdotal interest, but no clinical trial data supporting fenbendazole as a treatment for Lyme disease. Here’s what the evidence actually shows:
The theoretical mechanism
Fenbendazole binds to β-tubulin, blocking microtubule polymerization and disrupting intracellular transport and cell division. There is a related bacterial protein called FtsZ involved in bacterial cell division, including Borrelia (Lyme), and, in theory, fenbendazole’s binding to this protein could disrupt Lyme, malaria, toxoplasmosis, and other pathogens. Howirecovered This is a biologically interesting hypothesis, but it remains theoretical.
Immune modulation
Peer-reviewed studies support the premise that fenbendazole affects bone marrow and the immune system. In mouse models of autoimmune encephalitis, fenbendazole reduced disease incidence, clinical onset, duration, and severity in 75% of treated mice compared with controls — though the effect reversed 3 weeks after treatment was stopped. PubMed Central. Since much of chronic Lyme’s damage involves immune dysregulation, this is worth noting.
The parasite co-infection angle
One clinical perspective holds that Bartonella, Babesia, and Borrelia may persist, in part, because of underlying helminth (worm) infections that suppress immune function. Fenbendazole is used alongside ivermectin and other antiparasitics to address these worm co-infections, which may then allow standard Lyme treatments to work better. Lymebook: This is an integrative framing with some logic behind it, though again, no controlled trials.
The hepatotoxicity risk
This is real and documented. A case report describes a 46-year-old woman who developed acute hepatitis with jaundice, scleral icterus, and markedly elevated liver enzymes (AST 529, ALT 470) after self-treating chronic Lyme disease with internet-purchased fenbendazole. She had switched to a formulation with 10 times the potency two weeks prior. Lymescience This case gets cited frequently as a warning, and other benzimidazoles have known hepatotoxicity precedent.
Bottom line
There’s no peer-reviewed clinical evidence that fenbendazole treats Lyme directly. The community interest likely stems from three overlapping ideas: (1) the FtsZ bacterial tubulin hypothesis, (2) its immune-modulating properties, and (3) the possibility that undiagnosed helminth co-infections are complicating chronic Lyme cases. The hepatotoxicity case is a genuine caution, especially at higher doses. Anyone exploring this would want baseline liver function tests and careful dose management.
Parting Shot #3 from Mark Grenon about chlorine dioxide, which I would use to treat any tumor, along with fenben
Mark is available for consultations at [email protected]. His fees are modest.
Disclaimer: I have to tell you to tell you to seek medical advice here, but if you don’t take your own counsel, you are an idiot.