Study to Assess Safety and Efficacy of GKT137831 in Patients With Primary Biliary Cholangitis Receiving Ursodeoxycholic Acid.

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.

Inclusion Criteria:

1. Male or female aged 18 to 80 years, inclusive.

2. Willing and able to give written informed consent and to comply with the requirements
of the study.

3. PBC diagnosis as demonstrated by the presence of ≥ 2 of the following 3 diagnostic
factors:

- History of elevated ALP levels (> ULN) for at least 6 months

- Positive anti-mitochondrial antibody (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 (based on historic liver biopsy), including
non-suppurative, destructive cholangitis affecting mainly the interlobular and
septal bile ducts.

4. Serum ALP ≥ 1.5 x ULN.

5. Serum GGT ≥ 1.5 x ULN.

6. UDCA treatment for at least 6 months and stable dose for at least 3 months prior to
Visit 1.

7. Subjects being treated for pruritus with colestyramine must be on a stable dose of
colestyramine for at least 8 weeks prior to baseline/Day 1 (Visit 2). Subjects must be
willing and able to take colestyramine at least 2 hours before or after study
medication.

8. Female subjects of childbearing potential must use a highly effective method of
contraception to prevent pregnancy for 4 weeks before randomization and must agree to
continue strict contraception for 90 days after last administration of investigational
medicinal product (IMP). Male participants with female partners of childbearing
potential must be willing to use a condom and require their partner to use an
additional form of adequate contraception as approved by the Investigator. This
requirement begins at the time of informed consent and ends 90 days after the last
administration of IMP. Male study participants must also not donate sperm from
baseline until 90 days after the last administration of IMP.

Exclusion Criteria:

1. A positive pregnancy test or breast-feeding for female subjects.

2. Any hepatic decompensation, defined as a past or current history of hepatic
encephalopathy, gastrointestinal tract bleeding due to esophageal varices, or ascites.

3. International normalized ratio (INR) > 1.2 unless subject is on anticoagulant therapy.

4. ALT > 3 x ULN.

5. Total bilirubin > 1 x ULN.

6. Planned or current plasmapheresis or other extra-corporeal treatments (e.g., molecular
adsorbent recirculation system (MARS)) for treatment-refractory pruritus.

7. History of liver transplantation, current placement on a liver transplant list or
current Model for End Stage Liver Disease (MELD) score ≥ 15.

8. Cirrhosis with complications, including history or presence of: spontaneous bacterial
peritonitis, hepatocellular carcinoma.

9. Hepatorenal syndrome (type I or II) or Screening serum creatinine > ULN.

10. Competing etiology for liver disease (e.g., hepatitis C, active hepatitis B,
non-alcoholic steatohepatitis (NASH), alcoholic liver disease (ALD), autoimmune
hepatitis, primary sclerosing cholangitis, Gilbert's Syndrome).

11. Subjects receiving prohibited medications within 3 months of Screening (Visit 1)
according to the list (a, b and c) provided in Section 6.6.2.

12. Treatment with any investigational agent within 4 weeks of Visit 1 or 5 half-lives of
the investigational medicinal product (whichever is longer).

13. A history of long QT syndrome.

14. Evidence of any of the following cardiac conduction abnormalities during the screening
period:

- A QTc Fredericia interval >450 milliseconds for males and >470 milliseconds for
females.

- A second or third degree atrioventricular block not successfully treated with a
pacemaker.

15. History of cancer in the preceding 5 years, except adequately treated non-melanoma
skin cancer, carcinoma in situ of the cervix, in situ prostate cancer, in situ breast
ductal carcinoma, or superficial bladder cancer stage 0).

16. The occurrence of any acute infection requiring systemic antibiotic therapy within the
2 weeks prior the Screening Visit (Visit 1), or human immunodeficiency virus (HIV)
infection.

17. A history of bone marrow disorder including aplastic anemia, or marked anemia defined
as hemoglobin < 10.0 g/dL (or 6.2 mmol/L).

18. Any condition which, in the opinion of the Investigator, constitutes a risk or
contraindication for the participation of the subject in the study, or which could
interfere with the study objectives, conduct, or evaluation.