Vanderbilt Clinical Trials

1. Informed consent and assent (as applicable) 2. Age ≥6 months at time of baseline visit 3. Diagnosis of cholestatic liver disease with cholestatic pruritus based on the presence of chronic liver biochemical abnormalities (>90 days) and/or pathological evidence of progressive liver disease. 4. If taking antipruritics or ursodeoxycholic acid, the participant has to be on a stable dosing regimen (i.e., same dose and frequency in the 30 days prior to the screening visit and will continue this dosing regimen up to Week 40 [adjustment for body weight is allowed]). 5. Access to email or telephone for scheduled participant contacts and access to smart phone or tablet for PROs. 6. Ability to read and/or understand the questionnaires (both caregivers and participants ≥9 years of age). 7. For participants ≤18 years of age: Access to consistent caregiver(s) during the study.

Those who meet any of the following criteria are NOT eligible to participate in the study: 1. Diagnosis of ALGS, ICP, PBC, PFIC, or PSC with native liver. 2. Active atopic dermatitis or other non- cholestatic diseases associated with pruritus that are not controlled by standard treatment and that may interfere with the severity assessment of cholestasis-associated pruritus. 3. Decompensated cirrhosis or complications of cirrhosis (e.g., esophageal or gastric variceal bleeding in the last 6 months, high-risk esophageal or gastric varices, ascites, hepatic encephalopathy, hepatorenal syndrome). Patients with compensated cirrhosis with preserved hepatic synthetic function and absence of complications are eligible. 4. Suspected or proven cholangiocarcinoma or hepatocellular carcinoma. 5. Unstable and/or serious medical disease that is likely to impair the ability to participate in all aspects of the study, confound efficacy and/or safety assessments, or result in substantially shortened life expectancy (e.g., any active malignancy including hematological malignancy, end-stage heart failure, active infection, acute and chronic diarrhea). Exceptionally, previous history of malignancy, adequately treated/in remission, that in opinion of investigator and medical monitor does not impact participant safety and participation in the study, may be allowed. 6. Laboratory results during the screening visit as follows: 1. Platelet count ≤70,000/mm3. Patients with any condition that further increases bleeding risk are excluded. 2. Albumin <30 g/L 3. INR ≥1.5 (after intravenous or subcutaneous supplementation of vitamin K) 4. Total bilirubin >10 mg/dL 5. ALT >10× ULN 7. Use of an IBAT inhibitor within 8 weeks prior to the screening visit. 8. Known intolerance/hypersensitivity to maralixibat or its excipients. 9. History of nonadherence to medical regimens, unreliability, medical condition, mental instability, or cognitive impairment that, in the opinion of the investigator, could compromise the validity of informed consent, compromise the safety of the participant, or lead to nonadherence with the study protocol or inability to conduct the study procedures.