HOW fenbendazole works:

Fenbendazole belongs to a group of drugs called benzimidazoles. Its main target is a protein called tubulin, which cells use to build microtubules. Think of microtubules as the cell's: "Railroad tracks" that move materials around the cell. Structural supports that help the cell keep its shape. Tools needed for cells to divide and make new cells. In parasites: Fenbendazole binds to tubulin. This prevents microtubules from forming properly. The parasite can't absorb nutrients (especially glucose), can't function normally, and eventually dies.

​Why are researchers interested in it for cancer? Cancer cells also rely on microtubules to divide. Because of that, scientists have wondered whether fenbendazole might affect cancer cells in a similar way. In laboratory and animal studies, researchers have observed that fenbendazole may: Slow the growth of some cancer cells. Disrupt microtubules in certain cancer cells. Affect how some cells use glucose. Potentially make some cancer cells more sensitive to other treatments

This information has been taken from the National Library of Medicine at PubMed