Fenbendazole is an anthelmintic agent, which is used to treat parasites in domestic animals. It also has benzimidazole-based antitumor activity. Studies have shown that fenbendazole inhibits the growth of cancer cells by binding to b-tubulin microtubule subunits and disrupting tubulin polymerization. It has also been found to suppress RAS-related signaling pathway expression in lung adenocarcinoma (a cancer with mutations in the KRAS gene) cells.

A fenbendazole-based drug was developed by Stanford University researchers, and in mice, it appeared to reduce the size of tumors. This discovery led to the creation of a startup company called Benizole Therapeutics, which is trying to commercialize the drug. A Stanford virologist says he didn’t set out to fight cancer, but the lessons he and his team learned by developing new ways to combat viruses like hepatitis and the common cold have helped them develop a novel class of drugs that appear to be effective against cancer in mice.

The benzimidazole fenbendazole has been shown to effectively inhibit the growth of metastatic colorectal cancer (CRC) and reduce multidrug resistance by blocking the synthesis of DNA methyltransferase (MST). It was also found to enhance the cytotoxicity of 5-FU in 5-FU-resistant CRC cells. However, a detailed mechanism of action of this anthelmintic is not known.

Recently, self-administration of the anthelmintic fenbendazole by patients with a variety of different genitourinary malignancies has been reported on social media. A particular case report of a patient with advanced non-small cell lung cancer (NSCLC) who experienced tumor shrinkage after self-administration of fenbendazole has gained widespread attention on social media.

This patient’s underlying disease is a KRAS mutant advanced NSCLC. According to the case report, the patient was diagnosed with advanced NSCLC in March 2018. She was prescribed chemotherapy by her doctor, but due to side effects of the regimen, she decided to discontinue it and self-administered fenbendazole based on a veterinarian’s recommendation.

The patient began taking fenbendazole on May 31, and the results showed that her tumors started to shrink within two weeks. The tumors were fully shrunk by the time of the first MRI scan on July 12, and her doctor decided to stop her other chemotherapy treatments.

Despite this, claims of the ability of fenbendazole to cure cancer have not been proven in any clinical trials. The nonprofit organization Cancer Research UK told Full Fact that there is “insufficient evidence” that fenbendazole can cure cancer, and it hasn’t gone through the rigorous testing needed to prove its efficacy as a treatment. In addition, the FDA has not approved fenbendazole for treating fenbendazole for cancer