Efforts to thwart viral diseases like hepatitis or the common cold led Stanford virologist Jeffrey Glenn, MD, and his team to a drug that appears effective against cancer in mice. The drug, called fenbendazole (brand names Panacur and Safe-Guard), is an antiparasitic medication that has also been shown to slow down cancer growth in laboratory cells and animals.
Fenbendazole is a member of the benzimidazole class of anthelmintic drugs, and has long been used to treat parasitic infections in animals. The drug interferes with the formation of microtubules, structures inside cells that provide structure and help transport materials throughout the cell. In a recent study, the team showed that in colorectal cancer cells, fenbendazole significantly inhibited cell proliferation and induced apoptosis.
In human cancer patients, the drug has also been shown to improve outcomes when combined with other drugs. However, there isn’t enough evidence from randomized clinical trials to show that fenbendazole can cure cancer in people.
A few years ago, a woman in her 80s with advanced lung cancer was taking fenbendazole to treat parasitic infestations when she began experiencing severe liver injury. She subsequently stopped taking the drug and her liver injury resolved spontaneously. In an interview, she revealed that she had started taking fenbendazole because of social media reports suggesting it might be effective against cancer.
This case, along with several others, has raised interest in using a combination of conventional and alternative treatments to treat cancer. One of the most popular alternatives is immune checkpoint inhibitors, which block receptors on cancer cells that are typically overexpressed in tumors. Currently, there are over a dozen approved immune checkpoint inhibitors for various cancers.
Researchers have been studying whether a combination of immune checkpoint inhibitors can improve the effectiveness of treatment by targeting multiple pathways. But there’s also interest in using traditional chemotherapies with immunotherapy agents, including fenbendazole, which has been shown to have anti-tumor effects when combined with other cancer treatments.
Earlier research by the team demonstrated that fenbendazole could inhibit proliferation of colon cancer cells in a mouse model. The team also found that fenbendazole and another drug in the same family, mebendazole, reduced tumors when administered to animal models with different types of cancer.
In the current study, the team tested fenbendazole’s ability to induce G2/M arrest and apoptosis in 5-FU-sensitive and resistant SNU-C5 and SNU-C5/5-FUR CRC cells. They found that fenbendazole caused cell death by enhancing p53-mediated apoptosis and partly by inducing ferroptosis and necroptosis in both wild-type and mutant cells. In addition, they found that the drug caused a reduction in p21 expression in p53 mutant cells, and enhanced p53-independent apoptosis in these cells. They further found that fenbendazole inhibited RAS-related signaling pathways in cancer cells with a KRAS mutation. fenbendazole for cancer