Lack of evidence for cancer treatment protocol that recommends antiparasitic drugs ivermectin and mebendazole

In October 2024, social media posts and articles appeared, claiming that a cancer treatment protocol involving ivermectin and fenbendazole could cure cancer. One such post, which was liked more than 10,000 times on Instagram, cited the “peer-reviewed and published” protocol and claimed “Ivermectin and Mebendazole now proven to help with cancer”. The Gateway Pundit, which has published misinformation about COVID-19 and vaccines numerous times, also promoted the protocol in an article dated 14 October 2024.

The post and article are based on a 13 October 2024 tweet by William Makis (aka Viliam Makis), who currently has more than 290,000 followers on X (formerly Twitter). The tweet proclaimed: “BREAKING NEWS: First-in-the-World Ivermectin, Mebendazole and Fenbendazole Protocol in Cancer has been peer-reviewed and published on Sep.19, 2024!”

Makis previously worked at Cross Cancer Institute in Edmonton, Canada, as a nuclear medicine physician until October 2016, when his employment was terminated following complaints of professional misconduct.

After COVID-19 vaccines became publicly available, Makis propagated misinformation about the vaccines, falsely claiming that they cause “turbo cancer” and that 80 Canadian doctors died because of the vaccines. He was also a co-author of a flawed analysis of autopsies that concluded 74% of the people who were autopsied died because of the vaccines.

Although the College of Physicians & Surgeons of Alberta currently lists Makis’ medical license as inactive, his tweet implied he continues to dispense medical advice to patients (“Many of you know that I have been helping thousands of Cancer patients with high dose Ivermectin, Mebendazole, and Fenbendazole”).

We reached out to Makis for comment and will update this review with new information if it becomes necessary.

Ivermectin, mebendazole, and fenbendazole are drugs used to treat parasitic infections. Both ivermectin and mebendazole are used in humans, while fenbendazole is typically used in animals. Both mebendazole and fenbendazole belong to a class of drugs known as benzimidazole antihelmintics.

Science Feedback addressed viral cancer cure claims related to ivermectin and fenbendazole in earlier reviews, explaining that preclinical studies showed promising results, but that this isn’t sufficient to draw conclusions about the drugs’ effectiveness against cancer in people.

The peer-reviewed protocol co-authored by Makis also doesn’t provide sufficient evidence to support its recommendations. We explain below.

Protocol mainly based on preclinical studies and human studies unrelated to ivermectin and mebendazole’s effectiveness against cancer

The protocol, co-authored by Makis, was published in the Journal of Orthomolecular Medicine. The journal is of questionable credibility, as orthomolecular medicine, which holds that physical and mental illnesses can be treated with nutritional supplements, is a form of alternative medicine that largely lacks evidence to back it. The group that publishes the journal, the International Society for Orthomolecular Medicine, is listed among Quackwatch’s Questionable Organizations.

The protocol’s rationale for using ivermectin and mebendazole, among other things, leans heavily on in vitro studies that looked at cells growing in the laboratory and animal studies, as a perusal of pages 4 and 5 show.

To support its dosing recommendations for ivermectin and mebendazole, the protocol cited several scientific publications. However, none of these publications provide sufficient evidence showing that these drugs are effective against cancer in humans.

The two publications on ivermectin were a clinical trial by Guzzo et al. and a comment by de Castro et al. The clinical trial looked at healthy adults, not cancer patients, and studied the safety of relatively high doses of ivermectin^[1]. The comment examined the safety of high-dose ivermectin in patients with a type of leukemia, but this was done with a view to treat COVID-19 in cancer patients, not to treat cancer.

Among the four publications on mebendazole were two case reports, one by Dobrotskaya et al. and another by Chiang et al. Case reports describe and interpret individual cases, typically in a single patient or in very small groups of patients. They often document unique or unusual observations, which may provide leads for further investigation.

Dobrotskaya et al. described the case of a 48-year-old man with metastatic cancer, whose cancer remained stable for 19 months after he began taking mebendazole. However, his cancer began to worsen after 24 months.

Chiang et al. reported how three patients with urogenital cancers experienced significant improvements, such as tumor shrinking, after they began to take mebendazole. However, two of the three were also receiving conventional chemotherapy. Under these circumstances, it’s impossible to attribute their improvement solely to mebendazole.

These positive results led both case reports to call for further research on mebendazole’s anticancer effects in people. However, case reports alone cannot constitute sufficient evidence for guiding cancer treatment in patients: they’re essentially a form of anecdotal evidence and their very small sample sizes mean that their observations aren’t generalizable to the larger population.

The other two publications cited in favor of mebendazole and related drugs like fenbendazole for treating cancer were two reviews of the existing scientific literature. Both discussed extensively the potential anti-cancer effects of these drugs, but these effects were observed mainly in in vitro studies, which look at cancer cells growing in the laboratory, and animal studies. One of the reviews stated that “Clinical trials of benzimidazole anthelmintics have insufficient data to evaluate theier(sic) use in treating cancer”^[2].

In summary, the scientific evidence cited in the protocol cannot reliably answer the question of whether ivermectin and mebendazole are effective against cancer in people. Therefore, the claim that the protocol shows ivermectin and mebendazole can treat cancer in people is unfounded.

Randomized clinical trials better equipped to assess a drug’s effectiveness in people compared to preclinical trials and case reports

None of this is to say that ivermectin and mebendazole won’t have a place in cancer treatment eventually. It is true that these drugs have shown promising results in preclinical studies. However, preclinical studies alone cannot predict how well a drug works in people.

On a BreastCancer.org podcast in 2019, oncologist Brian Wojciechowski said that “in the lab when you have mice and you’re testing drugs on mice and they show promise, and then when they finally make it up to human beings, very, very few of these drugs actually work in humans”.

Indeed, a study that looked at clinical trial success rates found a 3.4% success rate for cancer-related clinical trials^[3].

However, studies in cells and animals do have their uses, mainly as stepping stones in research, paving the way for eventual clinical trials in humans. For example, a clinical trial is currently underway to evaluate a novel drug combination of ivermectin and an anticancer drug in breast cancer patients. A search on ClinicalTrials.gov also showed at least one ongoing clinical trial on mebendazole’s effect on cancer.

Randomized controlled trials (RCTs) are considered the gold standard for assessing the safety and efficacy of a drug^[4]. The design of these trials mitigates some biases that contribute to spurious results or obscure a true effect.

Randomization, when done properly, ensures that the control and treatment groups being compared are similar in characteristics like age, gender, and health status. This mitigates selection bias and increases confidence that an observed difference between the two groups is due to the intervention, rather than to any inherent differences in the groups’ characteristics.

Such trials may also include blinding. In double-blind RCTs, both the researchers and the participants don’t know which participants are in the control and treatment group. This mitigates various biases that can arise when researchers and participants change their behaviors or interpret findings differently due to knowledge of who’s receiving the intervention.

Conclusion

Ivermectin and mebendazole are approved antiparasitic drugs that have also shown promising anticancer effects in in vitro and animal studies. Clinical trials in humans to establish the effectiveness of these drugs against cancer will be needed to inform cancer treatment guidelines. Trials like these are currently underway.

But the cancer treatment protocol co-authored by Makis relied on in vitro and animal studies, anecdotal case reports, and studies that weren’t designed to assess the effectiveness of ivermectin and mebendazole against cancer. These scientific publications don’t constitute reliable scientific evidence to support calls by Makis and others to use ivermectin and mebendazole to treat cancer.

REFERENCES

• 1 – Guzzo et al. (2013) Safety, Tolerability, and Pharmacokinetics of Escalating High Doses of Ivermectin in Healthy Adult Subjects. Journal of Clinical Pharmacology.
• 2 – Son et al. (2020) The Antitumor Potentials of Benzimidazole Anthelmintics as Repurposing Drugs. Immune Network.
• 3 – Wong et al. (2019) Estimation of clinical trial success rates and related parameters. Biostatistics.
• 4 – Kabisch et al. (2011) Randomized controlled trials: part 17 of a series on evaluation of scientific publications. Deutsches Ärzteblatt.