Ok, this one might sound a little crazy.
Recently I was asked about using a veterinary anti-parasite drug, ie. a de-wormer, for the treatment of human cancer. As a naturopathic doctor who helps people fighting cancer, I am not a stranger to being asked about off-the-wall sounding cancer treatments. After all, if you’ve ever spent any time surfing on the internet for cancer cures you surely have seen the numerous things being called a cure.
However, I don’t consider it wise to off-handedly reject these questions. On more than one occasion I’ve learned of treatments and therapies that did actually help. Also, until we have a legitimate cure for this disease, I figure it’s at least worth a cursory look to see if there might be an inkling of validity to these new treatments.
This is how I ended up looking into the research on fenbendazole and cancer.
Fenbendazole is a veterinary drug used to treat intestinal parasites, like pinworms.
My go-to place for quick research is PubMed which is the National Library of Medicine and National Institutes of Health online database. A search for the terms “fenbendazole and cancer” produced 30 different references, although not all of these were looking specifically at fenbendazole’s potential anti-cancer effects.
Fenbendazole’s anti-cancer effects were first being reported as far back as 2005 (1). It started when cancer researchers who were trying to implant cancer cells into laboratory animals were having a tough time getting the cancer cells to take hold. In some of the animals, the cancer cells kept dying off. Eventually, it was discovered that animals that had been treated with fenbendazole, to either get rid of or prevent parasites, were the ones that didn’t get cancer.
Fenbendazole is in a class of medications called benzimidazoles, and the main action of these drugs is to inhibit tubulin polymerization. Drugs that inhibit tubulin polymerization are sometimes called microtubule inhibitors and are some of the most frequently used anti-cancer drugs. Taxane-based drugs and vinca alkaloid-based drugs are both examples of chemotherapy drugs that are microtubule inhibitors. Microtubules are like little ropes that are used to move things around the inside of a cell. They are especially important during cell division (aka. mitosis) when they move and separate chromosomes (genetic material) before it can be replicated. If a medication prevents microtubules from doing their job correctly, cell replication can’t be completed, and the cell will die. In cancer medicine, these drugs are used because cancer cells typically reproduce and divide faster than healthy cells.
In addition to being a microtubule inhibitor, Fenbendazole has also been found to have some additional anti-cancer properties including the inhibition of cancer cell energy metabolism and also inhibiting the negative regulators of the P53 gene- a tumor suppressor gene (2).
Looking at the available research on Pubmed, the first couple of articles that popped up were published in 2019. One paper reported that benzimidazoles promoted an upregulation of the P53 gene in melanoma and breast cancer cells (3). The P53 gene is called a tumor suppressor gene and it makes a protein which inhibits the growth and development of tumors. The P53 gene is notable because it is the most common gene mutation found in cancer cells, and when it is mutated it can’t do its job well. An upregulation of a working copy of the P53 gene is a good thing.
Another article published in 2019 was interesting in that it screened the benzimidazole class of drugs to see if they would have any action on a KRAS mutated non-small cell lung cancer (NSCLC). KRAS mutations are found in about 30% of NSCLC cases and to varying degrees in other cancers. KRAS is called an oncogene, and when it is mutated it can cause normal cells to become cancerous (4). The authors of the study, who were all from the National Cancer Research Institute in Japan concluded that “benzimidazole derivatives play an important role in suppressing KRAS-mutant lung cancer cells.” This is interesting because as of the time of publication there had been no other effective drug therapies found for targeting KRAS mutated cancer cells.
It was also reported that another benzimidazole drug called mebendazole- a close relative of fenbendazole- significantly extended mean survival up to 63% in syngeneic and xenograft orthotopic mouse glioma models (5). This is pretty impressive because glioblastoma multiforme is typically an aggressive and hard to control type of brain cancer. It is also worth noting that mebendazole has a well-established and long history of safe use in humans.
Mebendazole made some additional waves when it was found, along with other benzimidazole drugs, to have a potent ability to significantly inhibit the growth of and cause apoptosis in melanoma cells. This was true even for treatment-resistant melanoma cells. It was concluded that mebendazole was a potent melanoma-specific cytotoxic agent (6). Since that article was published a few other pieces of research have explored the use of benzimidazoles and melanoma.
Fenbendazole combined with certain vitamins was found to significantly inhibit the growth of implanted lymphoma cells in mice by researchers at John’s Hopkins (7). These researchers stated that their opinion was that cancer inhibition was a result of the microtubule inhibiting properties of fenbendazole. Interestingly, treatment with fenbendazole alone caused an increase in tumor growth. This was believed to be the result of a single outlier mouse in which cancer cells grew very quickly. It was felt that this one mouse was “experimental noise.” Doubly interesting was the fact that the use of vitamins AND fenbendazole had a better effect than vitamins alone, fenbendazole alone, or the control group.
Speaking of vitamins, yet another piece of research found that fenbendazole combined with vitamin E succinate was effective in producing cancer cell death in both mouse and human prostate cancer cell lines (8). This study used both hormonally sensitive and hormone insensitive prostate cancer lines. The combination of vitamin E succinate and fenbendazole was effective for all the cell lines tested. These researchers also took a group of mice and fed them a diet containing high levels of both fenbendazole and vitamin E succinate for 206 days. No toxicity was reported in these mice.
It seems there is some validity to the observation that benzimidazole drugs have anticancer potential. It is important to point out that most of the research on fenbendazole wasn’t done in humans, but on cell cultures in petri dishes. What is found in a lab doesn’t always translate to a similar finding in humans, although many people- and some marketing companies- will quickly make that leap.
So, is a drug the cancer cure? Not likely. Fenbendazole and other benzimidazole drugs certainly have some proven anti-cancer action. This action is best described as inhibiting the progression of cancer and even killing some difficult-to-treat cancer types including melanoma, lymphoma, lung cancer, prostate cancer, and glioblastoma.
I think that we will see more research on Fenbendazole and cancer treatment in the future. “Drug-repurposing,” finding new uses for old drugs, is a hot topic right now. In the meantime, I will continue to look into all the off-the-wall cancer treatments that come my way.
I’ll keep you posted.