Abstract: 5?-methylthioadenosine (MTA) is described as a compound that is susceptible to inhibiting and/or blocking the epithelial-mesenchymal transition (EMT), a process whereby epithelial cells become mesenchymal cells. The periodical intake of MTA [every 24 h for 21 days] significantly improves fibrosis and the markers for hepatic cellular damage in KO-Mdr2 mice with MTA (28 mg/kg). Following the daily oral administration of MTA, both the expression of EMT markers in the total liver and appreciable signs of fibrosis are significantly reduced, indicating the beneficial effect of MTA on the liver affected by the lack of Mdr2. MTA is proposed to be a safe drug, suitable for oral formulation and without secondary effects, to be used in the prevention and/or treatment of diseases associated with EMT, including chronic cholestatic diseases, fibrosis and cholangiocarcinoma.