A popular anthelmintic drug called fenbendazole has been reported to have antitumor effects and can be used in combination with a number of other treatments to increase their effectiveness. These findings have led to preclinical and clinical trials to determine whether fenbendazole can be an effective cancer treatment. This medication belongs to the family of benzimidazoles and is a common antiparasitic that is used in humans, dogs, cats, rabbits, ferrets, pigs, sheep, horses, and cattle. It is also widely used in veterinarian medicine to treat helminth parasites such as pinworms, roundworms, giardia, hookworms, whipworms, and Taenia solium.
This drug is taken orally and is available in tablets and liquid form. In general, fenbendazole does not have any side effects at normal doses. Some animals may react to the chemical, however, if it is given in higher than recommended doses. If this happens, seek veterinary care immediately. Some of the chemicals released by dying parasites may cause an allergic reaction in pets, such as facial swelling, itching, hives, vomiting, or shock.
Studies in mice have shown that fenbendazole inhibits tumor growth by altering the microtubules within cells. It does this by binding to tubulin, an important component of the cell’s cytoskeleton. This blocks the polymerization of microtubules, thereby interfering with cell-cycle progression and causing mitotic catastrophe.
In another study, a human nonsmall cell lung carcinoma cell line was treated with fenbendazole in vitro. The drug bound to b-tubulin, which was necessary for its polymerization inhibitory activity. This blocked the formation of mitotic spindles and prevented cyclin B1 from binding to CDK1 to initiate cell-cycle progression. As a result, the cell cycle was blocked at metaphase and the cancer cells died (Fig. 3).
The effect of fenbendazole was also tested in an animal tumor model using a mouse mammary carcinoma assay. When fenbendazole was administered prior to implantation, it significantly decreased tumor volume and vascularity. In addition, the tumors in the fenbendazole group were smaller than those in the control group. Initial complete blood counts showed that white cell counts were low in all groups. However, at the end of the experiment, all groups demonstrated a similar leukocyte response that consisted primarily of neutrophils.
The results of these studies indicate that fenbendazole may interfere with immune function and should be avoided during facility treatment of tumor models. Researchers should discuss this potential impact with their research animal’s veterinarian before starting treatment. Ideally, the veterinarian should recommend a reevaluation of the vaccine status of experimental animals after treatment with fenbendazole to ensure that immunity has not been compromised. In cases where a veterinarian feels that the benefits of treating an animal’s tumor outweigh this concern, researchers should consider utilizing only offspring from treated animals for tumor experiments. This would avoid the risk of unintended research complications resulting from long-term or permanent effects on immunity. However, this is not practical in many facilities due to the large numbers of animals that must be treated at once.fenben lab fenbendazol