Inclusion Criteria:

• Male and/or female subjects 18 years or older

• Cholestatic pruritus secondary primary biliary sclerosis (PBS) or primary sclerosing cholangitis (PSC).

• Pruritus that is chronic in duration (greater equal to 6 months)

• Pruritus severity with a peak pruritus numerical rating score of ≥ 5 (moderate severity).

• Model for End-Stage Liver Disease (MELD) score < 15. This will capture patients with chronic stable liver disease without significant comorbid conditions and/or signs of rapidly progressive or decompensated liver failure.

• Willingness and ability to comply with scheduled clinic visits, physical exams, laboratory tests, questionnaires, effective contraception use, and other trial procedures.

Exclusion Criteria:

• Pruritus due to a primary inflammatory skin dermatosis or other forms of psychogenic pruritus utilizing skin biopsies to exclude as needed.

• Pregnant females

• History of intrahepatic cholestasis of pregnancy

• Any form of chronic hepatic pruritus associated with underlying malignancy

• Liver transplant recipients

• Drug-induced liver pruritus.

• ALT or AST greater than 3 times the upper limit of normal or total bilirubin greater than 2 times upper normal limit.

• Advanced liver disease indicators including, ascites requiring therapeutic paracentesis, history of spontaneous bacterial peritonitis, any grade of hepatic encephalopathy, or a documented history of variceal bleeding within the preceding six months.

• Severe coagulopathy with INR > 15.

• Any form of acute cholestatic liver disease.

• Allergy to nemolizumab or its ingredients

• Inability to provide informed consent

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 03/20/2026. Questions regarding updates should be directed to the study team contact.