Ivermectin and Cancer: Why Does a Spark in the Laboratory Fail to Become a Treatment in Patients?

From an Oklahoma Businessman to Joe Rogan’s Microphone: A Historical and Sociological Examination of 10 Years of Medical Mythology

An Oklahoma businessman: Where the story begins

The central figure is an American businessman diagnosed with small-cell lung cancer in August 2016, whose metastatic disease spread to his neck, right lung, stomach, liver, bladder, pancreas and sacrum. He begins investigational treatment with pembrolizumab (Keytruda) in a clinical trial at MD Anderson Cancer Center. Three months later, his PET scan is clear. The decisive clinical factor here is that he is part of an immunotherapy trial with 1.100 participants (one thousand, one hundred).

However, he attributes his clear scan and long-term survival to something else: fenbendazole, a canine antiparasitic drug recommended by a veterinarian friend. The anecdote is embellished with a "rumour" that a scientist working at Merck Animal Health, diagnosed with stage 4 brain cancer, recovered with fenbendazole. The patient devises his own regimen: fenbendazole 222 mg, taken for three consecutive days followed by four days off, alongside vitamin E, curcumin and cannabidiol (CBD) oil. In later years, this combination would be called the "Tippens Protocol".

The epistemic point we need to underline here is: The patient’s investigational treatment with an anti-PD-1 monoclonal antibody is sufficient on its own to explain the clinical response. Although the outcomes of the 1.100 participants in that trial are unknown, it has long been known that pembrolizumab trials show a certain proportion of long-term responses in advanced lung cancer. Nevertheless, the story was a perfect narrative package for the voracious algorithms of the social media age: an expensive, "hidden" secret made available to the public; a dog medicine defeating oncology; the medical establishment ignoring it, knowingly or unknowingly.

South Korea: The narrative’s first global explosion

Tippens’s personal story became an international cultural event in an unexpected part of the world. In September 2019, a South Korean YouTube channel published his story; more than 2,4 million views within three months led to fenbendazole stocks running out in veterinary pharmacies nationwide after the video.

The cultural explosion peaked when a well-known comedian with lung cancer announced that he had started taking fenbendazole in September 2019 while continuing hospital chemotherapy. Yet this second element—the fact that standard treatment was being given concurrently—largely disappeared in media coverage. Viewers interpreted the story as "dog medicine alone defeating cancer". In September 2020, the comedian said he had "seen no effect"; he died in December 2021. Warnings from the Korean Medical Association, Pharmacists Association and Veterinary Medical Association could not keep pace with the viral cultural narrative.

This event is the first clear laboratory for a pattern that would recur in subsequent years: a patient receiving standard treatment while also using an antiparasitic drug improves, and the improvement is attributed to the antiparasitic. In the absence of controls, a causal connection and a comparison group, standard treatment becomes invisible while the marginal agent takes centre stage.

The COVID-19 bridge and ivermectin’s second rise

The Tippens story opened the door only for benzimidazoles: mebendazole, albendazole and fenbendazole. Ivermectin entered oncology through a different bridge, the COVID-19 pandemic. After an Australian in-vitro study in 2020 showed an inhibitory effect of ivermectin on SARS-CoV-2 in cell culture, the drug quickly became central to the discourse of "alternative treatment". Over the next three years, randomised controlled trials showed no meaningful clinical benefit of ivermectin in COVID-19, yet the social media ecosystem reinforced the drug: health authorities’ warnings were reframed as "suppression of evidence", strengthening a conspiracy template in which a cheap, off-patent, readily available drug was hidden by "Big Pharma".

When the COVID-19 wave receded, ivermectin inherited this cultural infrastructure: the same audience, social media channels and epistemic template now shifted into cancer discourse. In October 2024, a radiologist who had previously worked in Alberta, Canada, and whose licence is currently inactive published a protocol prioritising a combination of ivermectin, mebendazole and fenbendazole in the "Journal of Orthomolecular Medicine". It is notable that this journal is not an accepted publication within the academic oncology community, and that core areas of orthomolecular medicine have long appeared on Quackwatch’s list of questionable organisations. Nevertheless, the protocol spread rapidly on social media, presented as "peer-reviewed evidence".

Mel Gibson, Joe Rogan and the speed of the algorithm

The phenomenon’s arrival at the scale of a global public health issue was recorded on 9 January 2025. Appearing on The Joe Rogan Experience, one of the largest podcast platforms in the United States, actor Mel Gibson said that three friends diagnosed with stage 4 cancer "now had no cancer at all" after ivermectin and fenbendazole. The episode received more than 60 million views within a month of release.

A study published in JAMA Network Open in May 2026, examining electronic health records of more than 68 million patients in the US TriNetX research network, found that ivermectin–benzimidazole prescribing rates in the six months after the statement more than doubled compared with the same period of the previous year. The increase among cancer patients was approximately 2,5-fold; the largest increases were observed among men, white Americans, people aged 18-64 and those in southern states. During the same period, a medical oncologist at Tennessee Oncology reported that a colleague estimated that approximately 20 to 25 percent of patients seen in their own clinic were taking ivermectin.

What happens in the laboratory: What do these molecules do to cells?

The point that must be kept separate from the clinical evidence gap is: The preclinical biological rationale is legitimate and has been on academic oncology’s agenda for many years. This distinction must remain clear to separate limitless scientific scepticism from the exaggerations of the cultural narrative.

Benzimidazoles: Microtubule destabilisation and metabolic intervention

Mebendazole, albendazole and fenbendazole are antiparasitic drugs in the benzimidazole carbamate class. Their mechanism of action involves binding to the colchicine-binding site of β-tubulin and disrupting microtubule formation in mammalian cells as well as parasites. Microtubules are structural elements responsible for separating chromosomes during cell division; when destabilised, cells arrest in mitosis and programmed cell death, or apoptosis, is triggered. Antimicrotubule drugs used in clinical oncology, such as vincristine, vinblastine and paclitaxel, belong to the same mechanistic family.

Mebendazole’s anticancer signal was first reported in 2002 by a research team at MD Anderson Cancer Center. In subsequent years, researchers showed that, beyond binding tubulin, mebendazole inhibits multiple tyrosine kinases such as VEGFR2, BRAF and ERK, stabilises the p53 tumour-suppressor pathway, restricts tumour cell energy metabolism by inhibiting glucose uptake, and suppresses the glycolytic pathway through pyruvate kinase inhibition. In glioma models, oral mebendazole prolonged average survival in orthotopic mouse models by up to 63 percent.

This preclinical evidence base provided a foundation taken seriously by the academic drug-repurposing movement, particularly the "Repurposing Drugs in Oncology" initiative that developed around ecancer. Early-phase mebendazole trials have been or are being conducted in high-grade glioma (NCT01729260), colon cancer (NCT03925662) and recurrent glioblastoma (Reverse Swing-M Phase 1). Phase 1 studies showed relative safety even at high doses, but there is still no randomised comparative evidence demonstrating efficacy in humans.

Ivermectin: PAK1 inhibition and warming an immunologically cold tumour

Ivermectin is a macrocyclic lactone discovered in 1979 by Satoshi Ōmura at the Kitasato Institute and associated with the 2015 Nobel Prize in Physiology or Medicine—not for the drug itself, but for the scientific work underlying its discovery. Its antiparasitic effect relies on activating glutamate-gated chloride channels in target organisms, causing neuromuscular paralysis.

Ivermectin’s effects in cancer cells are evaluated through a different mechanistic network. The most frequently highlighted target in preclinical literature is p21-activated kinase 1 (PAK1). PAK1 is a junctional kinase at the intersection of Wnt/β-catenin, Akt/mTOR, MAPK and NF-κB pathways, and is overexpressed in many tumour types. Ivermectin suppresses this pathway network by directly inhibiting PAK1 activity or increasing its degradation. It has also been shown to affect YAP1 (the Hippo pathway), cancer stem cell markers and multidrug-resistance pumps (BCRP/ABCG2).

A particularly notable preclinical observation was published in 2020: a City of Hope research group showed that ivermectin could turn "cold" tumours, with limited T-cell infiltration, into "hot" tumours in mouse breast cancer models, potentially creating synergy with immune checkpoint inhibitors by inducing immunogenic cell death. This preclinical finding formed the rationale for the first Phase I/II trial conducted at Cedars-Sinai in subsequent years.

What do we know in humans? The Cedars-Sinai study and the overall gap

The first properly structured trial testing ivermectin’s synergistic effect with checkpoint blockade in breast cancer was conducted at Cedars-Sinai Medical Center with a Phase I/II design (NCT05318469). In patients with metastatic triple-negative breast cancer (mTNBC) who had received at least one or two lines of treatment, it combined ivermectin, given orally at 30-60 mg daily on days 1-3, 8-10 and 15-17 of 21-day cycles, with balstilimab, an anti-PD-1 monoclonal antibody.

Interim results presented at the 2025 ASCO Annual Meeting were as follows: of eight evaluable patients, one had a partial response (PR), one stable disease (SD) and six progressive disease (PD). Median progression-free survival was 2,5 months. The four-month clinical benefit rate was 37,5 percent. Adverse effects were reported as manageable, and the combination therefore as "safe and tolerable". According to Skyler Johnson of the University of Utah’s Huntsman Cancer Institute, commenting on the study, "one responding patient is the same number expected from the response rate of immunotherapy alone"; there is no evidence to say that ivermectin contributed additional benefit to the combination.

Studies of the same molecules in other cancer types are in early stages or do not exist. Most clinical literature still consists of case series and observational cohorts; their common limitations are the absence of a control group, selection bias and an inability to distinguish the effects of concurrent standard treatment. A study published in April 2026 in the open repository Zenodo, following patients taking ivermectin and mebendazole in an observational cohort design, reported signals of symptom improvement and quality of life. Its authors explicitly noted, however, that the data were hypothesis-generating and not equivalent to a peer-reviewed randomised comparison.

From Care Oncology to NCI: The face of legitimate repurposing

Outside this cultural narrative, an entirely different scientific movement exists and should not be confused with it. Founded in London in 2013, Care Oncology Clinic (COC) is a clinical initiative that prescribes metformin, atorvastatin, doxycycline and mebendazole together as an adjunct to standard oncology care. Its underlying hypothesis is to apply pressure from multiple directions to tumour cells’ metabolic dependencies; it aims to accumulate scientific data through patient observational cohorts. COC’s stance is notably cautious: it emphasises that the protocol does not replace standard treatment until evidence is established, requires physician supervision and involves regular monitoring of liver function.

On the academic side, a turning point came in February 2026. Anthony Letai, director of the American National Cancer Institute, announced that the institution was conducting a preclinical study of ivermectin’s ability to kill cancer cells. His own words were measured: "At the population level, it is very clear that this will not be a ‘cure-all’ for cancer." NCI’s decision prompted substantial debate among senior career scientists at the agency; some argued that resources were being diverted from stronger scientific priorities. Nevertheless, research resources being directed by the "intensity of interest" at an institutional level is an important development, acknowledging the phenomenon’s sociological scale on the scientific plane.

Lost treatment opportunities and liver injury: An inventory of clinical costs

The clinical cost of this phenomenon has two layers. The first, and less measurable, is the loss of a "treatment window". Physicians experienced in oncology know that, in certain cancer types, the timing of selecting successive treatment lines determines prognosis. A patient who departs from an evidence-based standard sequence and prioritises agents of undetermined value may miss an irreversible treatment window. This is particularly dangerous in stages where promptly initiating adjuvant, neoadjuvant or immune checkpoint treatment is critical.

The second cost is direct toxicity. A case published in ACG Case Reports Journal in May 2024 described the first histologically confirmed severe fenbendazole-associated drug-induced liver injury (DILI) in a human, a 67-year-old woman. After taking fenbendazole for a skin lesion, she presented with two weeks of jaundice, nausea, anorexia and dark urine. Aspartate aminotransferase was 1.869 U/L (one thousand, eight hundred and sixty-nine), alanine aminotransferase 2.600 U/L (two thousand, six hundred), total bilirubin 13,3 mg/dL and INR 1,6. Histology showed a hepatocellular pattern characterised by centrilobular hepatocyte necrosis; liver function normalised within three months after the drug was stopped.

A second case reported at the ACG Annual Meeting in October 2025 involved a patient with newly diagnosed ER−/PR−/HER2+ breast cancer. DILI detected at routine assessment before chemotherapy was linked to fenbendazole use and improved with N-acetylcysteine support. In the same year, hepatotoxicity in another patient taking ivermectin and fenbendazole while receiving nivolumab/relatlimab was published as "probable" fenbendazole DILI with a RUCAM causality score of 8, carrying a risk of confusion with immune checkpoint inhibitor-related hepatitis (ICI-H). This last case contains a distinct warning for physicians: Hepatitis arising in a patient receiving immunotherapy is automatically presumed to be immune-mediated and corticosteroids are started; yet the underlying cause may be off-label benzimidazole use that the patient has not disclosed.

The Turkish context is not unique within this international picture. Physicians with academic titles openly post on Turkish social media that antiparasitic agents are "effective" in cancer treatment, while patient communities—from Ekşi Sözlük threads and Şikayetvar comments to Evrim Ağacı’s question-and-answer platform and Facebook groups—reproduce the discourse. The frequency encountered in practice is probably different from the US estimate of 20-25 percent, but the observation that some oncology practices prescribe these agents to patients who have "run out of treatment options" is consistent with the global speed of the cultural narrative.

This article is for information and does not replace medical advice. When off-label or unapproved agents are being considered, the current level of evidence, expected benefit, potential interactions and toxicity risk profile should be assessed within the individual treatment plan only together with the relevant medical oncologist. Do not change your clinical decisions on the basis of personal testimonies, social media content or information in this article. Editorial note: the article was compiled from the Joe Tippens 2016 case anecdote, the South Korean viral explosion in 2019, the 9 January 2025 Mel Gibson episode of The Joe Rogan Experience, the 12 May 2026 JAMA Network Open analysis by Mafi and colleagues, the ACG Case Reports Journal 2024 fenbendazole DILI case, preliminary Cedars-Sinai NCT05318469 results at ASCO 2025, and NCI director Letai’s announcement in February 2026.