A Phase I/II Trial of JR-446 in Mucopolysaccharidosis Type IIIB (MPS IIIB)

A Global, Open-Label, Phase I/II Trial, to Evaluate Safety, Tolerability, Pharmacodynamic and Preliminary Efficacy of JR-446 in Mucopolysaccharidosis Type IIIB (MPS IIIB)

This is a global, open-label, Phase I/II, interventional trial in participants younger than 6 years of age with Mucopolysaccharidosis Type IIIB (MPS IIIB), designed to assess the safety and tolerability of JR-446, determine its pharmacodynamic effects, and explore its potential to demonstrate early clinical effects on disease-relevant outcomes.

Study Overview

• Status: Not yet recruiting
• Conditions: Mucopolysaccharidosis IIIB
• Intervention / Treatment: Drug: JR-446

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Phase 2; Phase 1

Contacts and Locations

• Study Contact: Name: JCR Pharmaceuticals Co., Ltd.; Phone Number: +81-797-32-8582; Email: clinical_development@jp.jcrpharm.com

Study Locations

• Germany
  • Hamburg, Germany, 20246
    • University Medical Center Hamburg-Eppendorf
    • Contact: Nicole Maria Muschol; Phone Number: +49 (0) 40 7410 53714; Email: muschol@uke.de
• United Kingdom
  • London, United Kingdom, WC1N 3JH
    • Great Ormond Street Hospital For Children
    • Contact: James Davison; Phone Number: 0074 0207 405 9200; Email: james.davison@gosh.nhs.uk
• United States
  • California
    • Oakland, California, United States, 94609
      • Children's Hospital Oakland Research Institution, Attn: 2900 Wing
      • Contact: Irene Chang; Phone Number: 415-476-2757; Email: Irene.chang@ucsf.edu
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15224
      • UPMC Children's Hospital of Pittsburgh
      • Contact: Deepa Rajan; Phone Number: 412-692-6787; Email: rajands@upmc.edu
  • Virginia
    • Fairfax, Virginia, United States, 22030
      • Lysosomal and Rare Disorders Research and Treatment Center (LDRTC)
      • Contact: Ozlem Goker-Alpan; Phone Number: 703-261-6220; Email: ogoker-alpan@ldrtc.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Patients with confirmed MPS IIIB with a phenotype of MPS IIIB that is not classified as slowly progressive (i.e., not attenuated).
2. A chronological age <6 years.
3. Ability to complete and achieve a Standard score ≥55, using either Bailey Scale of Infant Development-4 (BSID-4) Cognitive domain or Kaufman Assessment Battery for Children-II (KABC-II) Non-Verbal Index, whichever tool is most appropriate for the participant's chronological age.

Exclusion Criteria:

1. Contraindication for lumbar puncture or MRI.
2. A participant who has a medical condition or extenuating circumstance that, in the opinion of the principal investigator or sub-investigator, might compromise the participant's ability to comply with protocol requirements, the participant's well-being or safety, or the interpretability of the participant's clinical data.
3. A participant who has received any other investigational drug product (including but not limited to, tralesinidase alfa enzyme replacement therapy [TA-ERT], Genistein, KINERET [anakinra], ambroxol, miglustat) within 4 months (or 5 half-lives, whichever is longer) before the time of providing informed consent.
4. A participant who has received gene therapy treatment or hematopoietic stem cell transplantation (HSCT) with successful engraftment.
5. Serious drug allergy or hypersensitivity to any components of JR-446 or medications likely prescribed during the trial.
6. A participant has a history of bleeding disorder or current use of medications that, in the opinion of the investigator, place them at risk of bleeding following lumbar puncture.
7. A patient with recurrent epileptic seizures not adequately controlled with anti-seizure medication, and which, in the clinical judgment of the principal investigator, would preclude safe participation in the trial.
8. Serology consistent with human immunodeficiency virus (HIV) exposure or consistent with active hepatitis B (HepB) or hepatitis C (HepC) infection.
9. A participant/family, who, in the opinion of the investigator, may not be able to comply with protocol requirements and cooperate fully with the trial assessments, procedures, and scheduling for JR-446 IMP dose administrations.
10. Study participants for whom informed consent is unable to be provided by a parent or legal guardian; or when applicable for a study participant who is unable to provide assent with respect to study participation in conjunction with parental or legal guardian consent for participation on study.

The above information is not intended to contain all considerations relevant to a patient's potential participation in this clinical trial.

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-446; Arm: 1	Drug: JR-446; IV infusion

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
To establish the safety and tolerability of JR-446 in MPS IIIB patients following repeated dose administration	Incidence and severity of treatment-emergent adverse events; Incidence and severity of infusion-associated reactions; Incidence of clinically significant changes/abnormalities in safety laboratory tests, vital signs, and electrocardiogram.	Up to 1 year (multiple visits)

Secondary Outcome Measures

Outcome Measure	Time Frame
Change From Baseline in Cerebrospinal Fluid Heparan Sulfate Concentration	Through Week 53 (up to 1 year; multiple visits)
Absolute Change From Baseline in Serum Heparan Sulfate Concentration	Through Week 53 (up to 1 year; multiple visits)
Percent Change From Baseline in Serum Heparan Sulfate Concentration	Through Week 53 (up to 1 year; multiple visits)
Absolute Change From Baseline in Urine Heparan Sulfate Concentration	Through Week 53 (up to 1 year; multiple visits)
Percent Change From Baseline in Urine Heparan Sulfate Concentration	Through Week 53 (up to 1 year; multiple visits)
Absolute Change From Baseline in Serum Neurofilament Light Chain Concentration	Through Week 53 (up to 1 year; multiple visits)
Percent Change From Baseline in Serum Neurofilament Light Chain Concentration	Through Week 53 (up to 1 year; multiple visits)
Change in Cognitive Function Assessments From Baseline	Through Week 53 (up to 1 year)
Change in Brain MRIs From Baseline	Through Week 53 (up to 1 year)
Change in Height Standard Deviation Score (SDS) From Baseline (using WHO child growth standards)	Through Week 53 (up to 1 year)
Change in Weight SDS From Baseline (using WHO child growth standards)	Through Week 53 (up to 1 year)
Change in Body Mass Index (BMI) SDS From Baseline (using WHO child growth standards)	Through Week 53 (up to 1 year)

Collaborators and Investigators

• Sponsor: JCR Pharmaceuticals Co., Ltd.
• Collaborators: MEDIPAL HOLDINGS CORPORATION

Study record dates

Study Major Dates

• Study Start (Estimated): June 18, 2026
• Primary Completion (Estimated): June 30, 2028
• Study Completion (Estimated): September 30, 2028

Study Registration Dates

• First Submitted: May 14, 2026
• First Submitted That Met QC Criteria: June 8, 2026
• First Posted (Actual): June 11, 2026

Study Record Updates

• Last Update Posted (Actual): June 11, 2026
• Last Update Submitted That Met QC Criteria: June 8, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: JR-446-201

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