Anthelmintic

Fenbendazole is a veterinary dewormer. It is on this site because of a cancer claim that spread online from 2019 onwards, and the honest summary of that claim is short: there is no clinical trial evidence that fenbendazole treats cancer in humans. It does have real anti-proliferative activity in cell and animal models, through the same tubulin mechanism that kills worms. It also has real documented harm in people who have taken it for cancer: multiple published cases of severe drug-induced liver injury, including in a patient on immunotherapy where the liver damage was initially mistaken for an immune-related adverse event. A 2025 case series reporting benefit in three self-administering patients has been retracted.