Researchers in Canada are looking at how drugs commonly used to treat gastrointestinal disorders might augment the immune system‘s ability to fight cancer.

Many drugs modify the workings of the immune system to enhance anti-cancer immunity, but many also cannot be taken regularly because of their side effects. The researchers, working in mouse models, discovered that ranitidine and famotidine — over-the-counter antacids better known as Zantac and Pepcid AC  — were able to reduce the growth of breast cancer and its metastasis.

“The immune system plays an important role in defending against cancer,” Dr. Jean Marshall, a professor in the Department of Microbiology & Immunology at Dalhousie Medical School and the study’s principal investigator, said in a recent news release. “It can both reduce the incidence of initial tumour development and slow down or prevent cancer spread.”

Ranitidine and famotidine are non-prescription drugs often used to treat peptic ulcers and acid reflux, as well as for chemotherapy-related nausea in cancer patients. Both medications are safe and well-tolerated.

“Because cancer patients often take these drugs to reduce chemo side effects, our team … looked at how they impact function of the immune system in breast cancer,” said Dr. Marshall. “Our experiments have shown promising results; we found that daily treatment of ranitidine or famotidine inhibited the development and spread of breast tumours in mice.”

With financial support from the Canadian Cancer Society, the team will now conduct experiments to understand if these medications have a similar effect on other cancers as well as on the human immune system.

“Rantidine and famotidine have potential to safely prevent or slow down the development of cancer by boosting the immune response,” said Dr. Marshall. “If similar effects are seen in people, the drugs could aid in effective cancer immunotherapy or cancer prevention in those at high risk of developing the disease.”