An Extension Study of Maralixibat in Patients With Progressive Familial Intrahepatic Cholestasis (PFIC)

An Open-label Extension Study to Evaluate the Long-term Safety and Efficacy of Maralixibat in the Treatment of Subjects With Progressive Familial Intrahepatic Cholestasis (PFIC)

The primary objective of this open label extension study is to evaluate the long-term safety and tolerability of maralixibat.

Study Overview

• Status: Completed
• Conditions: Progressive Familial Intrahepatic Cholestasis (PFIC)
• Intervention / Treatment: Drug: Maralixibat

Detailed Description

The study will be conducted at multiple sites in North America, Europe, Asia, and South America.

• Study Type: Interventional
• Enrollment (Actual): 84
• Phase: Phase 3

Contacts and Locations

Study Locations

• Argentina
  • Buenos Aires, Argentina
    • Hospital Italiano de Buenos Aires
• Austria
  • Vienna, Austria
    • Medizinische Universität Wien, Universitätsklinik für Kinder- und Jugendheilkunde
• Belgium
  • Brussels, Belgium
    • Cliniques universitaires Saint-Luc
• Brazil
  • São Paulo, Brazil
    • Sociedade Beneficente de Senhoras Hospital Sírio-Libanês
• Canada
  • Alberta
    • Edmonton, Alberta, Canada
      • University of Alberta - Women and Children's Health Research Institute
• Colombia
  • Bogotá, Colombia
    • Fundacion Cardioinfantil
• France
  • Lyon, France
    • Groupement Hospitalier Est Hopital, Femme Mère Enfant de Lyon
  • Toulouse, France, 31059
    • CHU de Toulouse - Hôpital des Enfants
• Germany
  • Hanover, Germany
    • Medizinische Hochschule
• Italy
  • Bergamo, Italy, 24127
    • Azienda Ospedaliera Papa Giovanni XXIII - Unita di Pediatria
  • Roma, Italy
    • Ospedale Pediatrico Bambino Gesu'
• Lebanon
  • Beirut, Lebanon
    • Hotel Dieu de France, Alfred Naccache
• Mexico
  • Zapopan, Mexico
    • Consultario de Joshue David Covarrubias Esquer
• Poland
  • Warsaw, Poland
    • Instytut Pomnik Centrum, Zdrowia Dziecka
• Singapore
  • Singapore, Singapore
    • KK Women's and Children's Hospital
• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye), 34010
    • Koc University Hospital
• United Kingdom
  • Birmingham, United Kingdom
    • Birmingham Children's Hospital
  • London, United Kingdom
    • King's College Hospital NHS Foundation Trust
• United States
  • California
    • Los Angeles, California, United States, 90027
      • Children's Hospital Los Angeles
  • District of Columbia
    • Washington D.C., District of Columbia, United States, 20007
      • MedStar Georgetown University Hospital
  • Florida
    • Orlando, Florida, United States, 32803
      • Advent Health
  • New York
    • The Bronx, New York, United States, 10461
      • Children's Hospital at Montefiore
  • Ohio
    • Cincinnati, Ohio, United States, 45229
      • Cincinnati Children's Hospital
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15224
      • Children Hospital of Pittsburgh
  • South Carolina
    • Charleston, South Carolina, United States, 29425
      • Medical University of South Carolina
  • Texas
    • Dallas, Texas, United States, 75390
      • University of Texas Southwestern Medical Center
    • San Antonio, Texas, United States, 78229
      • University of Texas, Health Science Center San Antonio
  • Washington
    • Seattle, Washington, United States, 98105
      • Seattle Children's Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 1 year to 18 years (Child, Adult)
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

1. Provide informed consent and assent (as applicable) per Institutional Review Board/Ethics Committee (IRB/EC)
2. Completion of study MRX-502

Exclusion Criteria:

1. Any female who is pregnant or lactating or who is planning to become pregnant
2. Administration of prohibited medication between the MRX-502 EOT visit and the MRX 503 Baseline Visit (Day 0)
3. History of non-compliance in study MRX-502, non-adherence to medical regimens, unreliability, mental instability or incompetence that could compromise the validity of informed consent or lead to non-adherence with the study protocol based on Investigator judgment
4. Experienced an adverse event (AE) or serious adverse event (SAE) related to maralixibat during the MRX-502 study that led to permanent discontinuation of the subject from maralixibat
5. Any other conditions or laboratory abnormalities that, in the opinion of the Investigator or Sponsor Medical Monitor, may compromise the safety of the subject, or interfere with the subject participating in or completing the study
6. Cognitive impairment of the subject or caregiver that would, in the opinion of the investigator, preclude appropriate understanding of study information and compliance with study procedures

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Maralixibat; All subjects will receive Maralixibat oral solution	Drug: Maralixibat; All subjects will receive Maralixibat oral solution (up to 600 microgram per kilogram [mcg/kg]) twice daily

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean Change From Baseline Over Time in the Average Morning ItchRO(Obs) Severity Score	The Score on the ItchRo scale is a score on a 5-point scale from 0 (no itch) to 4 (very severe itch)	From Baseline to Weeks 75-78

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maintenance of ItchRO(Obs) Response (Weeks 15 - 26)	Maintenance of treatment effect is defined as the proportion of participants in the MRX-MRX treatment group (MRX-502 and MRX-503 data for subjects on MRX in the MRX-502 study) who obtain an ItchRO (Obs) response from Week 15 to Week 26 in Study MRX-503 in the primary cohort and PFIC cohort.	Week 15 - 26
Proportion of ItchRO(Obs) Responders Over Time	Proportion of ItchRO responders over time at each study visit using the 4-week study period prior to the visit as per ItchRO(Obs) responder definition.	Baseline to EOT
Mean Change From Baseline Over Time in the Average Morning ItchRO(Obs) Frequency Score	The Score on the ItchRo scale is a score on a 5-point scale from 0 (no itch) to 4 (very severe itch)	From Baseline to Weeks 75-78
Mean Change From Baseline Over Time in Total Serum Bile Acid (sBA) Levels	Mean change from baseline over time in total serum bile acid (sBA) levels	Baseline to week 70
Proportion of Subjects Who Experience an sBA Control Over Time From Week 18 to Week 26	Proportion of subjects who experience an sBA control over time from Week 18 to Week 26	From Week 18 to Week 26
Change From Baseline in Height Z-score	Height-for-age Z-score measures a participant's height relative to a reference population of children of the same age and sex. Z-scores were derived using World Health Organization growth charts for participants less than 24 months of age and Centers for Disease Control and Prevention growth charts for participants 24 months of age or older. A Z-score of 0 represents the population mean for age and sex. Positive Z-scores indicate height above the reference population mean, and negative Z-scores indicate height below the reference population mean. Higher Z-scores generally indicate greater linear growth relative to the reference population. Change from baseline was calculated as post-baseline height-for-age Z-score minus baseline height-for-age Z-score.	From baseline to Week 70
Change From Baseline in Weight Z-score	Weight-for-age Z-score measures a participant's weight relative to a reference population of children of the same age and sex. Z-scores were derived using World Health Organization growth charts for participants less than 24 months of age and Centers for Disease Control and Prevention growth charts for participants 24 months of age or older. A Z-score of 0 represents the population mean for age and sex. Positive Z-scores indicate weight above the reference population mean, and negative Z-scores indicate weight below the reference population mean. Higher Z-scores generally indicate greater body weight relative to the reference population. Change from baseline was calculated as post-baseline weight-for-age Z-score minus baseline weight-for-age Z-score.	From Baseline to Week 70

Collaborators and Investigators

• Sponsor: Mirum Pharmaceuticals, Inc.

Publications and helpful links

Helpful Links

• Genetics Home Reference - PFIC
• Mirum Pharmaceuticals homepage
• US FDA Resources

Study record dates

Study Major Dates

• Study Start (Actual): January 8, 2020
• Primary Completion (Actual): April 23, 2025
• Study Completion (Actual): April 23, 2025

Study Registration Dates

• First Submitted: December 2, 2019
• First Submitted That Met QC Criteria: December 2, 2019
• First Posted (Actual): December 4, 2019

Study Record Updates

• Last Update Posted (Actual): June 23, 2026
• Last Update Submitted That Met QC Criteria: May 27, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Pediatric; Digestive System Diseases; Liver Diseases; Mutation; Cholestasis; Maralixibat; PFIC; PFIC2; Bile Duct Diseases; Biliary Tract Diseases
• Additional Relevant MeSH Terms: Digestive System Diseases; Biliary Tract Diseases; Liver Diseases; Bile Duct Diseases; Digestive System Diseases; Liver Diseases; Biliary Tract Diseases; Cholestasis; Bile Duct Diseases; Cholestasis, progressive familial intrahepatic 1; maralixibat
• Other Study ID Numbers: MRX-503

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No