Therapy of Primary Sclerosing Cholangitis--Today and Tomorrow.

Primary sclerosing cholangitis (PSC) represents a fibro-obliterative bile duct disease with unpredictable individual clinical course that may progress to liver cirrhosis and malignancy. Due to our incomplete understanding of the etiology and pathogenesis of this disease, the therapeutic options are still rather limited. Bile acids play a key role in mediating cholangiocellular and hepatocellular injury in cholangiopathies such as PSC. Therefore, strategies targeting bile composition and homeostasis are valid approaches in PSC. Ursodeoxycholic acid (UDCA) is the paradigm therapeutic bile acid and its role in medical therapy of PSC is still under debate. Promising novel bile acid-based therapeutic options include 24-norursodeoxycholic acid (norUDCA), a side chain-shortened C23 homologue of UDCA, and bile acid receptor/farnesoid X receptor agonists (e.g. obeticholic acid). Other nuclear receptors such as fatty acid-activated peroxisome proliferator-activated receptors, vitamin D receptor and vitamin A receptors (retinoic acid receptor, retinoid X receptor) are also of potential interest and can be targeted by already available drugs. Furthermore, drugs targeting the gut-liver axis (e.g. intregrin blockers such as vedolizumab, antibiotics) appear promising, based on the close link of PSC to inflammatory bowel disease and the emerging relevance of the gut microbiome for the development of PSC. Finally, fibrosis represents a valid therapeutic target for anti-fibrotic drugs (e.g. simtuzumab) in PSC as paradigm fibro-obliterative disease. This review summarizes the current status and recent progress in the development of targeted therapeutic approaches based on increasing knowledge about the pathogenesis of this disease.