Study to Assess Safety & Efficacy of GKT137831 in Patients With Primary Biliary Cholangitis Receiving Ursodiol.

Primary biliary cholangitis (PBC) is a disease of the liver. It is caused a sustained attack by the body's immune system on the bile ducts (canals) inside the liver. This continuous assault leads to their gradual destruction and eventual disappearance. This results in obstruction to the flow of bile which gets worse with disease progression. Once the bile duct injury has been established, the disease progresses due to ongoing obstruction of bile flow, inflammation and scarring of the liver tissue(fibrosis). The liver eventually fails. This research is looking into whether the study drug is better than a dummy drug when given to patients with PBC. This trial will monitor the patients taking part with regular blood tests and ultrasound liver scans before, during, and at the end of the trial. These measures will allow for the ongoing assessment of liver function, and liver stiffness. It is hoped that in patients in whom the study drug is beneficial, the liver function or stiffness may progress at a slower pace, or may even improve during or at the end of the trial. Liver injury, inflammation and fibrosis Participants will be randomly assigned to 1 of 3 treatment groups (active drug once daily, active drug twice daily or placebo). This is a double blinded study so neither the participants nor the staff responsible for their care will know which group they have been assigned to. During the treatment period, participants will take 4 capsules orally at home in the morning and 4 capsules in the evening for 24 weeks. Participants will be in the trial for 32 weeks in total (about 8 months) and will attend approximately 8 clinic visits.