A popular antihelmintic drug used to treat parasites in dogs, fenbendazole (methyl [5-(phenylsulfanyl)-1H-benzimidazol-2-yl] carbamate), has been shown to have cytotoxic effects against human cancer cell lines. However, fenbendazole is not yet approved by the U.S. Food and Drug Administration for cancer treatment.

We investigated the effect of two commercial brands of fenbendazole on human cancer cells and found that both exhibited significant cytotoxic activity. The results suggest that further research on this compound should be carried out in order to develop a viable anticancer drug.

In our experiments, the cytotoxicity of fenbendazole for humans cancer was not significantly affected by hypoxia. Hypoxia was achieved by sealing cultures in glass bottles with rubber gaskets, inserting needles for influx and efflux of gases and by gassing with a mixture of 95% nitrogen/5% CO2 containing 1 ppm oxygen (2, 3, 4, 5, 8, 9, 10, 12).

Several studies have shown that fenbendazole has antitumor properties in human cancer cells and in mice. This is mainly due to its ability to interfere with the growth of microtubules, which provide structure to all living cells. This is a similar mechanism by which certain established cancer treatments such as vinblastine, vinorelbine and paclitaxel work, and it is therefore not a surprise that fenbendazole also exhibits antitumor properties (see references).

We conducted an experiment in which EMT6 tumors were either treated with three daily injections of fenbendazole or irradiated with 10 Gy. The growth curves of untreated and irradiated tumors were compared to that of the control. After a number of tumor measurements, mice were euthanized and necropsied. No signs of local invasion of the tumors into the skin or lymph nodes were observed, and lung metastases were not found in fenbendazole for humans treated and untreated mice (see Figure 3). fenbendazole for humans cancer