IBAT Inhibitor A4250 for Cholestatic Pruritus

Major Inclusion Criteria: * Diagnosis of PBC or PBC-Autoimmune hepatitis overlap as established according to American Association for the Study of Liver Diseases/European Association for the Study of Liver (AASLD/EASL) definitions. Definite or probable PBC diagnosis, as demonstrated by the presence of ≥ 2 of the following 3 diagnostic factors: * History of elevated alkaline phosphatase (ALP) levels (\>1.67 ULN) for at least 6 months prior to Day 1 * Positive antimitochondrial antibodies (AMA) titer or if AMA negative or in low titer (\<1:80) PBC specific antibodies (anti-GP210 and/or anti-SP100 and/or antibodies against the major M2 components (PDC-E2, 2-oxo-glutaric acid dehydrogenase complex) * Liver biopsy consistent with PBC; * Ursodeoxycholic acid (UDCA) non-responders defined as \>6 months of UDCA and at the time of enrolment a serum ALP \>1.67 ULN; * Laboratory markers of cholestasis identified within 3 months of Visit 1; * Treatment with cholestyramine at a dose \>4g BID or colestipol \> 5mg for at least 3 months; * The patient has a VAS-Itch of at least 30 mm during the day before baseline (Visit 2); * The patient is a male or non-pregnant female ≥18 years of age and ≤80 years of age with body mass index (BMI) ≥18.5 but \<35 kg/m2; Major Exclusion Criteria: * Any condition that, in the opinion of the Investigator constitutes a risk for the patient or a contraindication for participation and completion of the study, or could interfere with study objectives, conduct, or evaluations; * Jaundice of extrahepatic origin; * The patient has a structural abnormality of the GI tract; * The patient has a known, active, clinically significant acute or chronic infection, or any major episode of infection requiring hospitalization or treatment with parenteral anti infectives within 4 weeks of treatment start (study day 1) or completion of oral anti-infective treatment within 2 weeks prior to start of screening period; * The patient has unexplained and clinically significant GI alarm signals (e.g., lower GI bleeding or heme-positive stool, iron-deficiency anaemia, unexplained weight loss) or systemic signs of infection or colitis;