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Evaluating JR-141 for treating Mucopolysaccharidosis II

A Phase III Study of JR-141 in Patients With Mucopolysaccharidosis II (STARLIGHT)

Phase 3 Interventional JCR Pharmaceuticals Co., Ltd. · NCT04573023

This study is testing a new treatment called JR-141 for people with Mucopolysaccharidosis II to see if it works better and is safer than the current standard treatment.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment80 (estimated)
SexAll
SponsorJCR Pharmaceuticals Co., Ltd. Industry-sponsored
Locations29 sites (Phoenix, Arizona and 28 other locations)
Trial IDNCT04573023 on ClinicalTrials.gov

What this trial studies

This Phase III clinical trial is designed to assess the safety and efficacy of JR-141 in patients diagnosed with Mucopolysaccharidosis II. It is a global, multicenter, randomized, and assessor-blinded study that compares JR-141 to the standard treatment, Idursulfase. Participants will be monitored for their response to the treatment over a specified period, with a focus on both safety and therapeutic outcomes.

Who should consider this trial

Good fit: Ideal candidates for this study are patients with a confirmed diagnosis of Mucopolysaccharidosis II, including those who are naïve to treatment or stable on enzyme replacement therapy.

Not a fit: Patients who do not have a confirmed diagnosis of MPS II or those who are not eligible due to other health conditions may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new therapeutic option for patients with Mucopolysaccharidosis II, potentially improving their quality of life.

How similar studies have performed: Other studies have shown success with enzyme replacement therapies for Mucopolysaccharidosis, suggesting that this approach may also yield positive results.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* A patient who voluntarily signs an Institutional Review Board or Independent Ethics Committee-approved written informed consent form. If the patient 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 patient's legally acceptable representative (e.g., his/her parents or guardians) may sign the informed consent on behalf of the patient. Written informed assent should be obtained from the patient, wherever possible.
* Patients with confirmed diagnosis of MPS II
* Naïve patients or patients who are receiving stable enzyme replacement therapy with idursulfase for more than 12 weeks before starting administration of JR-141 or idursulfase for this study.
* Patients or patients whose partners are of child-bearing potential agree to use a medically accepted, highly effective method of contraception being use of condoms from the time of informed consent.

\<Cohort A\>

* Patients aged 36-42 months old at the time of ICF signing: patients must have a standard score measured by the BSID-III of 85 or less at screening.
* Patients aged 43-71 months old at the time of ICF signing: patients must EITHER have (1) A DQ measured by BSID-III of 20 to 85 at screening OR (2) A composite standard score on NVI measured by KABC-II of 85 or less at screening (only who can perform KABC-II)
* Patients aged 30-35 months old at the time of randomization and who are judged as having the severe phenotype by the Expert Board.

\<Cohort B\>

* Patients 6 years of age or older at the time of ICF signing and whose IQ are 70 and higher.
* Enrollment of subjects in Cohort B is contingent on the availability in that country of a validated country-specific version of the test (either WISC-V, WAIS-IV, or T.O.V.A.).
* Attenuated patients with 1 SD deficiency in the omission errors or variability domains of the T.O.V.A..

Exclusion Criteria:

* A patient with a history of HSCT with successful engraftment.
* A patient who has received gene therapy treatment at any point.
* Unable to undergo lumbar puncture.
* A patient who is enrolled in another clinical study that involves clinical investigations or use of any investigational product (drug or device) within 4 months before obtaining informed consent.
* Unable to comply with the protocol as determined by the principal investigator or subinvestigator.
* Judged by the principal investigator or subinvestigator to be ineligible to participate in the study due to a history of serious drug allergy or sensitivity including anesthesia or hypersensitivity to any component of JR-141.
* A patient who has a known or suspected local or general infection or is at risk of abnormal bleeding due to medical conditions or therapies.
* A patient who has documented mutation of other genes, including loci adjacent to the IDS gene that are known to be associated with developmental delay, seizures, or other significant CNS disorders.
* A patient who has documented loss of activity of sulfatases other than IDS.
* A patient who has had a ventriculoperitoneal shunt placed or any other brain surgery, or has a clinically significant ventriculoperitoneal shunt malfunction within 30 days of screening.
* full time employee of the sponsor or research site personnel directly affiliated with this study or their immediate family members.
* A patient who otherwise is judged by the principle investigator or sub-investigator to be ineligible to participate in the study.

\[Only in France\]

* Persons deprived of their liberty by a judicial or administrative decision, according to article L.1121-6 the Public Health Code (Code de la santé publique), 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 Code de la santé publique)

Where this trial is running

Phoenix, Arizona and 28 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Mucopolysaccharidosis II
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.