Fenbendazole is a benzimidazole that is well known as an antiparasitic agent. It is used against parasites in many species including pinworms, giardia, roundworms (including hookworms), whipworms, and Taenia solium and as an antihelmintic in dogs and other animals. It also has some antitumor effects in animal models and exerts polymerization inhibitory effects on microtubules which are components of the protein scaffolding that gives shape and structure to cells. These properties are similar to those of the cytotoxic anticancer agents vinca alkaloids and taxanes.
A 80-year-old woman with metastatic nonsmall cell lung cancer developed severe liver injury during pembrolizumab monotherapy and had her therapy temporarily discontinued. An interview with her family revealed that she had been self-administering oral fenbendazole, which is marketed as an anthelmintic for dogs, based on social media reports suggesting its effectiveness against cancer. The patient discontinued the fenbendazole and her liver injury resolved spontaneously.
In cell culture experiments, fenbendazole significantly inhibited microtubulin polymerization and thereby affected cellular viability. However, the drug did not significantly affect the growth of EMT6 tumors in vivo, even when administered in very high doses in combination with radiation or docetaxel. These data were in agreement with results from our previous experiment that compared the effect of three daily i.p. injections of fenbendazole to that of a fenbendazole-containing antihelmintic diet on the growth of EMT6 tumors in mice. The time to achieve a four-fold increase in tumor volume was not altered by the treatment regimen. fenbendazole for cancer