A few years ago a patient asked me about using a veterinary anti-parasite drug, fenbendazole, for the treatment of human cancer.  After 20 years of practicing as a naturopathic doctor helping people fight cancer, I have been asked about countless improbable sounding cancer treatments.   

However, I’ve learned over the years that it doesn’t hurt to consider some of these out of the norm treatments. More than once I’ve been surprised to find out that the treatment in question did in fact have the potential to help.  

With this in mind, I looked into the research behind fenbendazole and cancer treatment. 

Using the National Library of Medicine and National Institutes of Health online database I was able to find 30 different references regarding fenbendazole and cancer.  

Fenbendazole’s anti-cancer effects were first reported as far back as 2005.  The research paper described the difficulty cancer researchers were having trying to implant cancer cells into laboratory animals. Apparently, they 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 some of the animals had been treated with fenbendazole prior to get rid of or prevent parasitic infection. Those same mice who were treated with fenbendazole 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 some of the most frequently used anti-cancer drugs are of this type.  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, cellular 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, and inhibiting their microtubules causes the cancer cells to die. 

In addition to being a microtubule inhibitor, Fenbendazole has also been found to have some additional anti-cancer properties. This includes the inhibition of cancer cell energy metabolism and inhibiting the negative regulators of the P53 gene- a tumor suppressor gene.    

Another paper from 2019 reported that benzimidazoles promoted an upregulation of the P53 gene in melanoma and breast cancer cells.  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.  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 mouse glioma models.  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.  Since that article was published a few other pieces of research have explored the use of benzimadazoles and melanoma with impressive and promising results. 

Fenbendazole combined with certain vitamins was found to significantly inhibit the growth of implanted lymphoma cells in mice by researchers at John’s Hopkins.  These researchers stated that their opinion was that cancer inhibition was a result of the microtubule inhibiting properties of fenbendazole.  Interestingly, the use of vitamins AND fenbendazole had a better effect than vitamins alone, fenbendazole alone, or the control group.  

Another piece of research found that fenbendazole combined with vitamin E succinate was effective in causing cancer cell death in both mouse and human prostate cancer cell lines.  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.  

So, considering the above referenced research, it seems there is indeed some validity to the idea that benzimidazole drugs have anticancer potential.  It is important to point out that most of the research on fenbendazole wasn’t done in humans.  What is found in a lab animal or petri dish doesn’t always translate to a similar finding in humans, although many people- and some marketing companies- will try to convince you otherwise. 

So, is a fenbendazole the cancer cure?  Not likely.  Although, 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.