A POC and Dose-Ranging Study of HTD1801 in PSC Patients

Inclusion Criteria:

- Male or female between 18 and 75 years of age;

- Have a clinical diagnosis of PSC as evident by chronic cholestasis of more than six
months duration with either a consistent magnetic resonance cholangiopancreatography
(MRCP)/endoscopic retrograde cholangiopancreatography (ERCP) showing sclerosing
cholangitis;

- If subjects have Inflammatory Bowel Disease (IBD) they will be eligible to
participate. If a subject has IBD, documented evidence of IBD must have been evident
by prior endoscopy or in previous medical records for ≥6 months. In addition, subjects
may only enter the study with a Partial Mayo Score of 0-4, inclusively. Subjects who
are on treatment are allowed, provided they are stable for 3 months if taking:

1. 5-amino salicylic acid drugs,

2. azathioprine,

3. 6-mercaptopurine, or methotrexate

4. biologics;

- Have a serum ALP ≥1.5 × upper limit of normal (ULN);

- Be able to understand and sign a written informed consent form (ICF);

- Subjects receiving allowed concomitant medications need to be on stable therapy for 28
days prior to the Baseline visit, with the exception of ursodeoxycholic acid (UDCA),
which should be stable for at least 6 weeks prior to the Baseline visit.

Exclusion Criteria:

- Presence of documented secondary sclerosing cholangitis (such as ischemic cholangitis,
recurrent pancreatitis, intraductal stone disease, severe bacterial cholangitis,
surgical or blunt abdominal trauma, recurrent pyogenic cholangitis,
choledocholithiasis, toxic sclerosing cholangitis due to chemical agents, or any other
cause of secondary sclerosing cholangitis) on prior clinical investigations;

- Small duct PSC;

- Presence of percutaneous drain or bile duct stent;

- History of cholangiocarcinoma or clinical suspicion of new dominant stricture within 1
year by MRCP/ERCP. Presence of dominant stricture without ERCP evidence of
cholangiocarcinoma is acceptable if stable for ≥ 1 year;

- Ascending cholangitis within 60 days prior to Screening;

- History of alcohol or substance abuse or dependence;

- Prior or planned liver transplantation;

- Presence of alternative causes of chronic liver disease, including alcoholic liver
disease, nonalcoholic steatohepatitis, primary biliary cirrhosis, autoimmune
hepatitis;

- Platelet count below 125,000/mm3, albumin below 3.0 g/dL, International Normalized
Ratio (INR) > 1.2, or a history of ascites, or encephalopathy, or history of
esophageal variceal bleeding;

- Severe active IBD or flare in colitis activity within the last 90 days requiring
intensification of therapy beyond baseline treatment;