Inclusion Criteria:

- Weight ≥ 35 kg

- Previous cholangiographic evidence of PSC by magnetic resonance cholangiopancreatography (MRCP) or direct cholangiography or liver biopsy findings

- Serum GGT ≥ 2 × upper limit of normal (ULN)

- On a stable UDCA treatment regimen for ≥ 8 weeks

Exclusion Criteria:

- Secondary sclerosing cholangitis

- Percutaneous or endoscopically-placed biliary drain or stent

- History of cholangiocarcinoma or clinical suspicion of new dominant stricture within 1 year

- Ascending cholangitis requiring intravenous antibiotic therapy within 60 days prior to Screening

- Concomitant overlap syndrome with primary biliary cholangitis (PBC)

- Significant hepatic decompensation

- Alternative causes of chronic liver disease

- Hospitalization for colitis within 30 days prior to Screening

- Serum creatinine > 1.2 x ULN

- Hemoglobin < 10 g/dL

- Glucose-6-phosphate dehydrogenase (G6PD) deficiency