for males (full criteria)
at Oakland, California and other locations
study started
estimated completion
Principal Investigator
by Paul Harmatz



A Global Phase III multicenter, randomized, assessor-blinded, active-controlled designed to evaluate safety and efficacy of study drug for the treatment of the MPS II.


Mucopolysaccharidosis II, Mucopolysaccharidoses, Idursulfase, JR-141 or Idursulfase, JR-141 2.0 mg/kg/week


You can join if…

Open to males

  • 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 parents or guardians) may sign the informed consent on behalf of the patient. Written informed assent should be obtained from the patient, wherever possible.
  • Males 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.
  • Male 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>

  • Males aged 36-42 months old: patients must have a standard score measured by the BSID-III of 85 or less at screening.
  • Males aged 43-71 months old: 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 (only who can perform KABC-II)
  • Males 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>

  • Males aged 6 years or older and whose IQ are 70 and higher.
  • Attenuated patients with 1 SD deficiency in the omission errors or variability domains of the T.O.V.A..

You CAN'T join if...

  • Use of gene therapy or hematopoietic stem cell transplantation (HSCT), excluding those who need enzyme replacement therapy even after HSCT.
  • Unable to undergo lumbar puncture.
  • A patient who has received other investigational product (drug or device) within 4 months before study enrollment.
  • 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 sensitivity to 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 a medical condition or therapy.
  • 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)


  • UCSF Benioff Children's Hospital Oakland accepting new patients
    Oakland California 94609 United States
  • Ann & Robert H. Lurie Children's Hospital of Chicago accepting new patients
    Chicago Illinois 60611 United States

Lead Scientist at UCSF

  • Paul Harmatz
    Professor, Pediatrics, School of Medicine. Authored (or co-authored) 211 research publications


accepting new patients
Start Date
Completion Date
JCR Pharmaceuticals Co., Ltd.
Phase 3 research study
Study Type
Expecting 80 study participants
Last Updated