The anthelmintic fenbendazole is a moderate microtubule destabilizing agent with multiple mechanisms of action. These include crosslinking, adenosine triphosphate inhibition, and modulation of the cellular radiosensitivity pathway. Our purpose is to test the hypothesis that fenbendazole, which is well tolerated in veterinary practice as an antihelmintic and has a safety profile similar to anthelmintics, may also exhibit antitumor activity in cancer patients.
A dog with metastatic melanoma received pembrolizumab in early July 2019. She had recently undergone an 8-wk facility treatment for Aspiculuris tetraptera pinworms and was on a fenbendazole diet. Her CEA levels increased, and her family obtained information on the Internet indicating that oral fenbendazole could be used as an adjunct to chemotherapy for dogs with cancer. They purchased fenbendazole and the dog orally self-administered it.
Subcutaneous flank xenografts of EMT6 cells were implanted in BALB/c mice and allowed to grow until they reached a calculated volume of 1000 mm3. Mice were stratified by tumor volume into groups and treated as indicated (Table 1). Diet alone did not affect tumor growth but combined with fenbendazole, administered as three daily i.p. injections, significantly inhibited the rate of tumor growth in unirradiated but not irradiated tumors.
2-h fenbendazole treatments were toxic to aerobic EMT6 cell cultures and produced a steep decrease in cell numbers even at concentrations approaching the limit of drug solubility. These cytotoxic effects, however, did not correlate with radiation sensitivity in the EMT6 culture model or in solid tumors in mice.fenben lab fenbendazol fenben lab fenbendazol