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

Starting soon · Phase 1/Phase 2

Conditions studied: Mucopolysaccharidosis IIIB

In brief

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.

Key facts

Study ID

NCT07640984

Run by

JCR Pharmaceuticals Co., Ltd.

People needed

12

Starts

2026-06-18

Expected to finish

2028-09-30

Last updated by the study team

2026-07-07

Who can join

Age: any, up to 5. Sex: any. Healthy volunteers: not accepted.

You may qualify if…

• Patients with confirmed MPS IIIB with a phenotype of MPS IIIB that is not classified as slowly progressive (i.e., not attenuated).
• A chronological age <6 years.
• 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.

You may not qualify if…

• Contraindication for lumbar puncture or MRI.
• 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.
• 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.
• A participant who has received gene therapy treatment or hematopoietic stem cell transplantation (HSCT) with successful engraftment.
• Serious drug allergy or hypersensitivity to any components of JR-446 or medications likely prescribed during the trial.
• 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.
• 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.
• Serology consistent with human immunodeficiency virus (HIV) exposure or consistent with active hepatitis B (HepB) or hepatitis C (HepC) infection.
• 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.
• 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.

Where it is running

• Children's Hospital Oakland Research Institution, Attn: 2900 Wing — Oakland, California, United States
• UPMC Children's Hospital of Pittsburgh — Pittsburgh, Pennsylvania, United States
• Lysosomal and Rare Disorders Research and Treatment Center (LDRTC) — Fairfax, Virginia, United States
• University Medical Center Hamburg-Eppendorf — Hamburg, Germany
• Great Ormond Street Hospital for Children — London, United Kingdom

Full record on ClinicalTrials.gov

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