The internet is filled with videos claiming dog dewormer fenbendazole cures cancer. The drug isn’t an approved cancer treatment in humans, but it has been shown to suppress cancer cells outside of living things and in mice. It appears to work by stopping the proper growth of microtubules, polymers that bind together and provide structure for all cells. Microtubules are a common target for cytotoxic anticancer drugs.

But the fenbendazole claims on TikTok and Facebook are unfounded. A nonprofit organization called Cancer Research UK told AFP there’s insufficient evidence that the medication can cure cancer and is safe for people. It’s also important to understand that social media posts may be misleading, and people should always consult a doctor before self-administering medications or supplements.

In a study published in Scientific Reports, researchers found that fenbendazole inhibited cell proliferation and promoted death in colorectal cancer cells in the lab (in vitro). They also found that it caused p21 expression to increase in the cells, which blocks progression from G2 to mitosis. The researchers also observed that fenbendazole caused apoptosis in the cells through mitochondrial injury and caspase-3-poly(ADP-ribose) polymerase pathways. They further found that fenbendazole caused decreased GPX4 expression and that this led to ferroptosis in the cells, a form of autophagy in which damaged or toxic proteins are broken down.

A separate study conducted by Dr. Robert Riggins found that mebendazole, an antiparasitic drug similar to fenbendazole, suppressed pancreatic cancer in mice by causing the cancer cells’ tubulin to collapse. The drug, which is often prescribed to treat parasitic infections including roundworms, hookworms and pulmonary paragonimias, works by cutting off the parasites’ supply of nutrients.