A Study to Extend Treatment with JR-141 after Completion of Study JR-141-GS31
Research type
Research Study
Full title
An Extension Study of JR-141 to Evaluate the Long-term Safety and Efficacy in Mucopolysaccharidosis Type II (Hunter Syndrome) Subjects
IRAS ID
1011247
Contact name
Sairei So
Contact email
Sponsor organisation
JCR Pharmaceuticals Co., Ltd.
Clinicaltrials.gov Identifier
Research summary
MPS II (Hunter syndrome) is a rare genetic disorder where the body does not produce enough of an enzyme called iduronate-2-sulfatase (IDS) that breaks down large sugar molecules called glycosaminoglycans (GAGs) in the body. Due to the lack of this enzyme, these molecules
accumulate in different organs of the body, leading to an increase in the size of these organs and other changes to the body, including but not limited to the head, lips, nose, and tongue. It can cause joint stiffness and changes in behavior.
Currently, there is only one approved treatment called idursulfase (ELAPRASE®) for MPS II patients in the UK. Idursulfase has been shown to improve clinical symptoms. However, it does not penetrate the blood-brain barrier. Therefore, it does not break down GAG accumulation in
the brain which causes the neurologic symptoms of MPS II.
The study drug, JR-141, has been designed to cross into the brain and deliver active enzymes there as well as in other body organs. JR-141 is currently being studied in a Phase III study (JR141-GS31) to evaluate its efficacy and safety compared to the standard of care therapy,
idursulfase. This study (JR-141-GS32) is the extension of the Parent Study (JR-141-GS31); its objective is to evaluate the long-term efficacy and safety of JR-141 on patients with MPS II.
This study can include participants who meet the following study rules including:
○ Patients with MPS II (Hunter Syndrome) who participated in and completed the Parent Study (JR-141-GS31)
○ The investigator determines there are no safety concerns to participate in this study
Participants will receive JR-141 intravenously at the dose of 2.0 mg/kg of body weight once every week, for a maximum duration of four years.
This study is sponsored by JCR Pharmaceuticals Co., Ltd.REC name
North East - Newcastle & North Tyneside 2 Research Ethics Committee
REC reference
25/NE/0147
Date of REC Opinion
22 Sep 2025
REC opinion
Further Information Favourable Opinion