To Assess Safety, Tolerability and Efficacy of LJN452 in Patients With Primary Bile Acid Diarrhea.

Key Inclusion Criteria: * A history of diarrheal symptoms for at least 3 months prior to dosing - Average stool frequency of at least 2 per day when off therapy AND Average stool form of \>5 on Bristol Stool Chart. * Previous laboratory or radiological confirmation of bile acid malabsorption with either fecal bile acid loss OR 7 day 75Selenium homocholic acid taurine (75SeHCAT) retention. * Age ≥ 18 years. Key Exclusion Criteria: * Patients with other diagnoses leading to diarrhea, including colorectal neoplasia, ulcerative colitis, Crohn's disease, celiac disease, chronic pancreatitis, drug-induced diarrhea or active infection AND Patients who have not been investigated by standard clinical assessments to exclude these disorders. * Treatment with bile acid sequestrants (colestyramine, colestipol, colesevelam) for 2 weeks before the first dose of LJN452. A washout of 14 days for these agents will be allowed before first dosing. * Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant. * A positive Hepatitis B surface antigen or Hepatitis C test result. * History of immunodeficiency diseases, including a positive HIV (ELISA and Western blot) test result.