Fenben lab fenbendazole is an antihelmintic drug in the broad-spectrum class of benzimidazole carbamate anthelmintics (I coined it benz). It has been used as an anthelmintic for dogs and cats for nearly six decades. Benzimidazoles also have activity against the trematodes that cause gastrointestinal diseases in humans and are commonly prescribed to treat Giardia spp. in dogs and cats with diarrhea due to this trematode species.
These drugs are highly effective against a wide range of parasitic infections. Recently, a study indicated that the same anthelmintics that kill parasitic worms might also be effective against cancer cells. These findings were the inspiration for a study investigating whether fenbendazole and related anthelmintics could enhance the effectiveness of other cancer treatments.
Intensive treatments of fenbendazole in vitro and in vivo decreased the growth of EMT6 mammary tumors in mice, and it significantly enhanced the potency of radiation and the antineoplastic drug docetaxel in combination regimens. However, a very small number of human cancer cell lines were resistant to these drugs, suggesting that fenbendazole and the anthelmintic class as a whole may have limited value in human cancer therapy.
The fenbendazole analytical standard and two commercial Brand P and Brand S samples were purchased from Sigma-Aldrich (Louis, MO). Sodium dihydrogen phosphate dehydrate, hydrochloric acid, HPLC grade water, and acetonitrile for LC-MS analysis were obtained from Macron Fine Chemicals (Arnhem, Netherlands). Cell proliferation was determined using the AlamarBlue assay and the IC50 values for each sample were calculated. All three samples were subjected to dissolution testing using a USP Apparatus 2, Model RCZ-8B Type Medicine Dissolving Instrument with paddles. The results of the dissolution tests indicated that the powdered samples were difficult to dissolve and had a poor solubility in phosphate buffer solution.