Cancer is responsible for an intolerable number of casualties in Canada every year. We have discovered a drug that is not a chemotherapeutic agent but causes cancer cells to become highly susceptible to anticancer chemotherapy. The drug is known as adiphenine and was developed many years ago as an orally active smooth muscle relaxant to treat urinary, biliary and intestinal colic. The pharmacological properties of adiphenine are known and hence it could be rapidly repurposed as a chemo-sensitizing agent. We propose to further strengthen our preliminary findings and to test the efficacy of adiphenine with chemotherapy in mouse models of breast cancer. Positive findings from our proposed studies could be rapidly translated into improved cancer treatment and ultimately result in better outcomes for cancer patients.