A popular cancer-treating drug being touted on TikTok and Facebook as a cure for advanced lung cancer is fenbendazole, which is usually prescribed to humans to treat parasites (roundworms, hookworms, whipworms, and some tapeworms). A video circulating on TikTok claims that the medication can also kill cancer in people. A Canadian veterinarian — known online as “Dr Joe Tippens” — is behind the video, which has been viewed more than 61,000 times. While some preclinical studies are examining these medications as possible anti-cancer agents, none has yet found enough evidence that they work.
The fenbendazole for humans cancer claims are based on anecdotal evidence, and it is unclear how many of these videos have been independently verified or created by Dr Joe Tippens. The fenbendazole for cancer treatment video also contains a disclaimer that it is not intended as medical advice.
However, research has shown that fenbendazole does slow down cancer cell growth in petri dishes and mice. The medication works by blocking a protein that is involved in cellular processes including cell division. This mechanism of action is similar to the hypoxia-selective nitroheterocyclic cytotoxic drugs and radiosensitizers that have been approved for cancer treatment, such as paclitaxel and vincristine.
Several pathways are involved in the growth of cancer cells, but one important pathway is through microtubule formation. Drugs that destabilize microtubules or inhibit tubulin polymerization block these pathways and may induce cell death. Fenbendazole for humans cancer is a moderate microtubule destabilizer and inhibits the assembly of spindles that separate chromosomes during mitosis. This may cause cells to enter mitosis without completing the separation process. Alternatively, it may also inhibit the progression of the cell cycle into metaphase or anaphase by inhibiting cyclin B1 binding to CDK1.
In the experiments shown in Figure 1, untreated EMT6 tumors in BALB/c mice were measured three times per week from when they became palpable until they reached a mean volume of about 1000 mm3. Then, the mice were divided into groups and treated with either the control drug, fenbendazole alone, or fenbendazole plus 10 Gy of x-ray radiation. The tumors of all groups were measured after treatment and at necropsy; there were no differences in weight or appearance between the drug treated groups and the control groups.
Similarly, the effects of 2 and 24 h fenbendazole treatments on cell viability were evaluated by counting colonies created from the monolayer cells. Both 2 and 24 h fenbendazole treatment resulted in decreases in the number of colonies, but yield-corrected survivals were lower for treated cultures compared to controls. This suggests that fenbendazole interferes with the ability of cells to complete the cell cycle, but the effect is less dramatic than for other cytotoxic agents that also act as mitotic catastrophe inhibitors. Moreover, the survival results show that fenbendazole has no synergistic effect with radiation. This is consistent with the hypothesis that the toxicity of fenbendazole and hypoxia-selective cytotoxic drugs and radiosensitizers is independent of the mechanism of cell death.