Mucopolysaccharidosis IIPhase 2/3NCT04348136
An Extension Study of JR-141 in Patients With Mucopolysaccharidosis Type II
A Phase 2/3 study testing JR-141 in people with Mucopolysaccharidosis II, run by JCR Pharmaceuticals Co., Ltd. at 20 sites in Japan.
Trial summary
Multicenter, open-label, single-group, designed to evaluate the long term efficacy and safety of study drug for the treatment of the MPS II. Read more about this study
- Who is it for?
- Any age, men only
- Conditions the study is for
- Mucopolysaccharidosis II
- What is being tested?
- JR-141
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 27 participants
- Where
- 20 sitesJapan
- Study dates
- 1 Sep 2019to 31 Mar 2030
- Phase
- Phase 2/3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages Any age
- Men only
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- A patient who participated in the preceding Study JR-141-301 and completed the Week 52 visit, and has no safety concerns to enter this study in the opinion of the investigator or subinvestigator.
- A patient capable of providing written informed consent in person (However, this is not required for patients aged younger than 20 years at the time of consent or patients with intellectual disability associated with MPS II whose willingness cannot be verified.)
- For patients aged younger than 20 years at the time of consent or patients with intellectual disability associated with MPS II whose willingness cannot be verified, written consent must be obtained from the legally acceptable representative. (Wherever possible, written consent of the patient should be obtained.)
- Male patient whose partner is of child-bearing potential and agrees to use a medically accepted, highly effective method of contraception.
Who cannot join
- A patient who used any concomitant medication or therapy that could affect study assessments in the opinion of the investigator or subinvestigator.
- A patient with a history of serious drug allergy or hypersensitivity that precludes participation in this study in the opinion of the investigator or subinvestigator.
- A patient judged to be ineligible by the investigator or subinvestigator for other reasons.
Trial locations and contacts
20 sites in 1 country.
20 sites in 1 country
Japan20 sites
Fukui Clinical site
Fukui, 910-1193
Fukuoka Clinical site 2
Fukuoka, 813-0017
Fukuoka Clinical site
Fukuoka, 830-0011
Gifu Clinical site
Gifu, 501-1194
Hiroshima Prefectural Hospital
Hiroshima, 734-8530
Hokkaido Clinical site
Hokkaido, 063-0005
Kananagawa Ckinical site
Kanagawa, 232-8555
Kumamoto Clinical site
Kumamoto, 860-8556
Okayama Clinical site
Okayama, 701-1192
Okayama Clinical site 2
Okayama, 710-8602
Okinawa Clinical site
Okinawa, 903-0215
Osaka Clinical site 3
Osaka, 534-0021
Osaka Clinical site 2
Osaka, 545-8586
Osaka Clinical site
Osaka, 565-0871
Saitama Clinical site
Saitama, 330-8777
Shizuoka Clinical site
Shizuoka, 420-8660
Shizuoka Clinical site 2
Shizuoka, 426-8677
Tochigi Clinical site
Tochigi, 329-0498
Tokyo Clinical site
Tokyo, 157-8535
Tottori Clinical site
Tottori, 683-8504
About this study
Multicenter, open-label, single-group, designed to evaluate the long term efficacy and safety of study drug for the treatment of the MPS II.
- Conditions
- Mucopolysaccharidosis II
- Being tested
- JR-141
- Medical subject headings
- Mucopolysaccharidosis II
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
JR-141Drug
IV infusion, 2.0 mg/kg/week
| Study group | Role | What they receive |
|---|---|---|
| JR-141 | Experimental | Not described Receives: Drug: JR-141 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Occurrence of adverse events
Measured: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Occurrence of adverse reactions
Measured: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Incidence of abnormal vital signs
Laboratory tests (hematology)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Incidence of abnormal vital signs
Laboratory tests (biochemistry)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Incidence of abnormal vital signs
Laboratory tests (iron-related tests)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Laboratory tests (urinalysis)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (pulse rate)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (body temperature)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (blood pressure)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
12-lead electrocardiogram
The presence or absence of abnormal findings (if present, specific findings and whether or not they are reported as adverse events)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Antibody tests (anti-JR-141 antibodies)
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
IAR
Measured: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Time course of developmental assessment data (Kyoto Scale of Psychological Development 2001) from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of developmental assessment data (Vineland-II) from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of developmental assessment data (Bayley-III or KABC-II) from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of CSF substrate (HS and DS) concentrations from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of serum HS and DS concentrations from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of urinary HS concentration from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of urinary DS concentration from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of uronic acid concentration from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of liver volume (assessed by CT or MRI) from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of spleen volume (assessed by CT or MRI) from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of cardiac function (assessed by echocardiography) from initial dosing in the preceding study
Measured: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of 6-minute walk test distance from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of joint range of motion from initial dosing in the preceding study
Measured: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Apr 2020
- Study start1 Sep 2019
- Primary completion31 Mar 2030 (estimated)
- Study completion31 Mar 2030 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Mucopolysaccharidosis IIStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2/3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 27 participants (actual)
Sponsor and investigators
- Lead sponsor
- JCR Pharmaceuticals Co., Ltd.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04348136
- Sponsor's protocol ID
- JR-141-302
- Status last verified
- Aug 2026
- First submitted
- 18 Dec 2019
- Last updated
- 3 Sep 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 3 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Extension Study of JR-141 in Patients With Mucopolysaccharidosis Type II
- ClinicalTrials.gov ID
- NCT04348136
- Acronym / sponsor ID
- JR-141-302
- Conditions
- Mucopolysaccharidosis II
- Phase
- Phase 2/3
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 27 participants (actual)
- Lead sponsor
- JCR Pharmaceuticals Co., Ltd.Industry (pharma, biotech, devices)
- Study start
- 1 Sep 2019 (actual)
- Primary completion
- 31 Mar 2030 (estimated)
- Study completion
- 31 Mar 2030 (estimated)
- First posted
- 16 Apr 2020 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Multicenter, open-label, single-group, designed to evaluate the long term efficacy and safety of study drug for the treatment of the MPS II.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| JR-141 | Experimental | Drug: JR-141 |
Who may qualify
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (4 listed)
- A patient who participated in the preceding Study JR-141-301 and completed the Week 52 visit, and has no safety concerns to enter this study in the opinion of the investigator or subinvestigator.
- A patient capable of providing written informed consent in person (However, this is not required for patients aged younger than 20 years at the time of consent or patients with intellectual disability associated with MPS II whose willingness cannot be verified.)
- For patients aged younger than 20 years at the time of consent or patients with intellectual disability associated with MPS II whose willingness cannot be verified, written consent must be obtained from the legally acceptable representative. (Wherever possible, written consent of the patient should be obtained.)
- Male patient whose partner is of child-bearing potential and agrees to use a medically accepted, highly effective method of contraception.
Key exclusion criteria (3 listed)
- A patient who used any concomitant medication or therapy that could affect study assessments in the opinion of the investigator or subinvestigator.
- A patient with a history of serious drug allergy or hypersensitivity that precludes participation in this study in the opinion of the investigator or subinvestigator.
- A patient judged to be ineligible by the investigator or subinvestigator for other reasons.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| JR-141IV infusion, 2.0 mg/kg/week | Drug | JR-141 |
Primary outcome
Occurrence of adverse events
Time frame: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Occurrence of adverse reactions
Time frame: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Incidence of abnormal vital signs
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Laboratory tests (hematology)
Incidence of abnormal vital signs
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Laboratory tests (biochemistry)
Incidence of abnormal vital signs
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Laboratory tests (iron-related tests)
Laboratory tests (urinalysis)
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (pulse rate)
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (body temperature)
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Vital signs (blood pressure)
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
12-lead electrocardiogram
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
The presence or absence of abnormal findings (if present, specific findings and whether or not they are reported as adverse events)
Antibody tests (anti-JR-141 antibodies)
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
IAR
Time frame: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years
Time course of developmental assessment data (Kyoto Scale of Psychological Development 2001) from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of developmental assessment data (Vineland-II) from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of developmental assessment data (Bayley-III or KABC-II) from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of CSF substrate (HS and DS) concentrations from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of serum HS and DS concentrations from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of urinary HS concentration from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of urinary DS concentration from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of uronic acid concentration from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of liver volume (assessed by CT or MRI) from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of spleen volume (assessed by CT or MRI) from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of cardiac function (assessed by echocardiography) from initial dosing in the preceding study
Time frame: Week 78, 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of 6-minute walk test distance from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Time course of joint range of motion from initial dosing in the preceding study
Time frame: Week 104, an average of 52 weeks after Week 104, up to approximately 10.6 years
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 3 Sep 2026.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
20 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2/3 study testing JR-141 in people with Mucopolysaccharidosis II, run by JCR Pharmaceuticals Co., Ltd. at 20 sites in Japan.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 3 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 20 sites in Japan. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Occurrence of adverse events (time frame: From the start of study (Week 52 of preceding study) up to the end of study, up to approximately 10.6 years). The study lists 25 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 3 Sep 2026.