A Proof-of-Concept and Dose-Ranging Study Investigating the Efficacy and Safety of HTD1801 in Adult Subjects With Primary Sclerosing Cholangitis (PSC)

• 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:

‣ 5-amino salicylic acid drugs,

⁃ azathioprine,

⁃ 6-mercaptopurine, or methotrexate

⁃ 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.