An Extension Study of JR-141 to Evaluate the Long-term Safety and Efficacy in MPS II (Hunter Syndrome) Subjects

An Extension Study of JR-141 to Evaluate the Long-term Safety and Efficacy in Mucopolysaccharidosis Type II (Hunter Syndrome) Subjects

An extension of Global Phase III open-label, multicenter designed to evaluate the Long-term safety and efficacy of study drug for the treatment of the MPS II.

Study Overview

• Status: Enrolling by invitation
• Conditions: Mucopolysaccharidosis II
• Intervention / Treatment: Drug: JR-141

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Phase 3

Contacts and Locations

Study Locations

• Argentina
  • Buenos Aires, Argentina
    • Hospital Universitario Austral
• Brazil
  • Porto Alegre, Brazil
    • Hospital de Clinicas de Porto Alegre
  • São Paulo, Brazil
    • Instituto de Genética e Erros Inatos do Metabolismo
• France
  • Bron, France
    • Hôpital Femme Mère Enfant
• Germany
  • Hamburg, Germany
    • Universitätsklinikum Hamburg-Eppendorf
• Italy
  • Rome, Italy
    • Osp. Pediatrico Bambino Gesù, IRCCS
• Poland
  • Krakow, Poland
    • Uniwersytecki Szpital Dziecięcy
• Spain
  • Barcelona, Spain
    • Hospital Sant Joan De Deu
• United States
  • California
    • Oakland, California, United States, 94609
      • UCSF Benioff Children's Hospital Oakland
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19104
      • Children's Hospital of Philadelphia

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. A subject who participated in the Parent Study (JR-141-GS31) and completed the assessments at Week 105 in Cohort A or Week 53 in Cohort B before being administered the study medication of that respective visit, and in the opinion of the principal investigator there are no safety concerns.
2. A subject from whom an IRB or IEC-approved written informed consent can be obtained, which is voluntarily signed. If the subject is aged under 18 years (aged under 16 years in the UK) at the time of enrollment or willingness to participate in the study cannot be confirmed due to MPS II-related intellectual disability, the subject's legally acceptable representative (e.g., his parents or guardians) may sign the ICF on behalf of the subject. Written informed assent should be obtained from the subject, wherever possible.
3. Female subject of child bearing potential or male subject whose female partner is of child-bearing potential, i.e., fertile, following menarche and until becoming post-menopausal unless permanently sterile, agrees to use a medically accepted, highly effective method of contraception from the time of signing the ICF. The method of contraception must be used during the study until 90 days for male subjects, and 30 days for female subjects after the final study drug administration.

Exclusion Criteria:

1. A subject who changed treatment from JR-141 to idursulfase during the treatment period in the Parent Study (JR-141-GS31).
2. A subject who is unable to comply with the protocol (e.g., is unable to return for safety evaluations or is otherwise unlikely to complete the study) as determined by the principal investigator or sub-investigator.
3. [Only in France] Persons deprived of their liberty by a judicial or administrative decision, according to article L. 1121-6 of the Public Health Code (Code de la santé publique, CSP) adults who are the subject of a measure of legal protection or unable to express their consent according to article L. 1121-8 of the CSP.

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: JR-141 2.0 mg/kg/week	Drug: JR-141; IV infusion, 2.0 mg/kg/week

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in neurocognitive testing, calculated by the Wechsler, from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study		[B-1: Week 78, 105, 157, 209, 261] [B-2: Week 78, 105, 131, 157, 209, 261]
Change in heparan sulfate concentrations in cerebrospinal fluid from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study to each time point	Assessment will be mandatory for the first two years after starting JR-141 administration through the parent study or the extension study.	[A-1, A-2, A-3: Week 157, 209, 261] [A-4: Week 131, 183, 235, 287]
Change in neurocognitive testing, calculated by the BSID-III or KABC-II, from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study		[A-1: Week 157, 209, 261] [A-2: Week 131, 157, 183, 209, 261] [A-3: Week 131, 157, 209, 261 ] [A-4: Week 131, 157, 183, 235, 287]
Change in neurocognitive testing, calculated by the VABS-II from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study		[A-1: Week 157, 209, 261] [A-2: Week 131, 157, 183, 209, 261] [A-3: Week 131, 157, 209, 261 ] [A-4: Week 131, 157, 183, 235, 287][B-1: Week 78, 105, 157, 209, 261] [B-2: Week 78, 105, 131, 157, 209, 261]

Secondary Outcome Measures

Outcome Measure	Time Frame
Change in liver and spleen volume from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study	[A-1, A-3: Week 157, 209, 261] [A-2: Week 131, 157, 209, 261] [A-4: Week 131, 183, 235, 287] [B-1: Week 105, 157, 209, 261] [B-2: Week 78, 105, 157, 209, 261]
Change in 6-minute walk distance from each subject's first administration of JR-141 throughout the Parent Study (JR-141-GS31) or this study	[B-1: Week 105, 157, 209, 261] [B-2: Week 78, 105, 157, 209, 261]

Collaborators and Investigators

• Sponsor: JCR Pharmaceuticals Co., Ltd.

Study record dates

Study Major Dates

• Study Start (Actual): February 22, 2023
• Primary Completion (Estimated): February 28, 2028
• Study Completion (Estimated): February 28, 2028

Study Registration Dates

• First Submitted: October 6, 2022
• First Submitted That Met QC Criteria: October 21, 2022
• First Posted (Actual): October 26, 2022

Study Record Updates

• Last Update Posted (Actual): January 21, 2026
• Last Update Submitted That Met QC Criteria: January 19, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Connective Tissue Diseases; Neurobehavioral Manifestations; Heredodegenerative Disorders, Nervous System; Intellectual Disability; Genetic Diseases, X-Linked; Carbohydrate Metabolism, Inborn Errors; Lysosomal Storage Diseases; Mucinoses; Mucopolysaccharidoses; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Nutritional and Metabolic Diseases; Skin and Connective Tissue Diseases; X-Linked Intellectual Disability; Mucopolysaccharidosis II
• Other Study ID Numbers: JR-141-GS32

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