Phase 2a Evaluation of Safety, Tolerability, and Pharmacokinetics of PLN-74809 in Patients With Primary Sclerosing Cholangitis (PSC)

Inclusion Criteria:

   - Established clinical diagnosis of large duct PSC based on an abnormal cholangiography
   as assessed by magnetic resonance cholangiopancreatography (MRCP), endoscopic
   retrograde cholangiopancreatography (ERCP), and/or percutaneous transhepatic
   cholangiopancreatography (PTC) in the context of cholestatic liver chemistry

   - Suspected liver fibrosis, as defined by liver stiffness measurement (LSM), assessed by
   ultrasound-based transient elastography (TE, FibroScan®) OR Enhanced Liver Fibrosis
   (ELF) Score OR Historical liver biopsy showing fibrosis without cirrhosis (by any
   scoring system) OR Magnetic resonance elastography (MRE)

   - Serum ALP concentration within normal limits or > 1 times the upper limit of normal
   (ULN)

   - Participants receiving treatment for IBD are allowed, if on a stable dose from
   screening and expected to remain stable for the duration of the study

   - Serum AST and ALT concentration ≤ 5 times the upper limit of normal

   - If receiving treatment with UDCA, therapy is at a dose of < 25 mg/kg/day, has been
   stable for at least 3 months before screening.

Exclusion Criteria:

   - Other causes of liver disease, including secondary sclerosing cholangitis or viral,
   metabolic, or alcoholic liver disease, as assessed clinically

   - Known or suspected overlapping clinical and histologic diagnosis of autoimmune
   hepatitis

   - Small duct PSC with no evidence of large duct involvement (evidence of PSC on
   historical liver histology, with normal bile ducts on cholangiography)

   - Presence of liver cirrhosis as assessed by liver histology, ultrasound-based liver
   stiffness measurement, ELF score, MRE, and/or signs and symptoms of hepatic
   decompensation (including but not limited to, jaundice, ascites, variceal hemorrhage,
   and/or hepatic encephalopathy.

   - Serum ALP concentration > 10 times the upper limit of normal.