A popular online claim that fenbendazole, an anthelmintic drug commonly used to treat gastrointestinal parasites such as pinworms, giardia, roundworms, hookworms, whipworms, and Taenia solium, can also cure cancer has been proven false. The claim is based on the anecdotal evidence of a cancer patient who experienced remission after self-administering fenbendazole in combination with conventional chemotherapy and radiation therapy. While a number of studies in cell cultures and mice suggest that fenbendazole might have anti-cancer effects, the patient’s case raises concerns about disseminating unproven medical information via social media.

A paper published Jan. 22 in Science Translational Medicine reports that the benzimidazole compound fenbendazole, known commercially as Panacur and Safe-Guard, blocks the growth of certain cancer cells by interfering with cellular processes essential to their survival. The research, led by Stanford University School of Medicine professor Michael Glenn, was a complex endeavor that required collaborations across multiple academic disciplines.

In this study, fenbendazole was shown to interfere with the formation of microtubules, a protein scaffold that gives shape and structure to cells. Microtubules are formed by a polymer called tubulin, which is assembled and disassembled by proteins such as c-Myc and MAP2K. The cytoskeleton is critical for many cellular functions, including the movement of organelles, cell division, and the transport of cargo across a cell’s membrane. The authors report that fenbendazole interferes with microtubule assembly by inhibiting the polymerization of tubulin.

As a result, the cytoskeleton becomes unstable and collapses under its own weight, which results in cell death. The fenbendazole-induced apoptosis and cell cycle arrest in colorectal cancer (CRC) cells is partly mediated by activating wild-type p53 and p21 pathways, but it is also due to the inhibition of autophagy, necroptosis, and ferroptosis.

The researchers also found that fenbendazole, when given to human volunteers in a randomized placebo-controlled first-in-human single-dose escalation trial, caused few adverse events or deaths. The team concludes that fenbendazole, or its active metabolite, oxifendazole, is an ideal candidate for development as an anti-cancer agent because of its safety and tolerability profile in humans.

The study was funded by grants from the National Institutes of Health, the NIH Director’s New Innovator Award, and ViRx@Stanford, a National Institutes of Health Center for Translational Research. Coauthors of the paper include Tara Williamson, Michelle Carvalho de Abreu, Dimitri G. Trembath, Cory Brayton, Byunghak Kang, Paulo Pimentel de Assumpcao, and Janet M. Cerutti. The authors report financial interest in Benizole Therapeutics, PBC. The paper’s author disclosures are available on the journal website. The journal is open access. fenbendazole for cancer