An Extension Study of JR-171-101 Study in Patients With Mucopolysaccharidosis Type I (MPS I)

Patients who have completed the Part2 of JR-171-101 study (NCT04227600) and fulfill all eligibility criteria can be enrolled in this JR-171-102 study. In the JR-171-102 study, subjects will receive either 2.0 or 4.0 mg/kg/week of JR-171 intravenously at the same doses received at Week 12 of the JR-171-101 study.

• JR-171 (Drug), also known as lepunafusp alfa: Intravenous (IV) infusion

Primary outcomes

• Number of participants with Adverse Events [156 weeks]: Adverse events
• Incidence of abnormal laboratory test results [156 weeks]: Hematology
• Incidence of abnormal laboratory test results [156 weeks]: Biochemistry
• Incidence of abnormal laboratory test results [156 weeks]: Serum iron tests
• Incidence of abnormal laboratory test results [156 weeks]: Urinalysis
• Incidence of abnormal vital signs [156 weeks]: Pulse rate
• Incidence of abnormal vital signs [156 weeks]: Body temperature
• Incidence of abnormal vital signs [156 weeks]: Blood pressure
• Incidence of abnormal vital signs [156 weeks]: Body weight
• Incidence of abnormal EKG readings [156 weeks]
• Number of participants with Adverse Events [156 weeks]: Anti-human-α-L-iduronidase antibodies
• Number of participants with Adverse Events [156 weeks]: Anti-JR-171 antibodies
• Number of participants with Adverse Events [156 weeks]: Infusion associated reaction (IAR)

Secondary outcomes

• Change From Baseline in Heparan Sulfate Levels in Cerebrospinal Fluid (CSF) [Weeks 26, 52, 104, 156]
• Change From Baseline in Dermatan Sulfate Levels in Cerebrospinal Fluid [Weeks 26, 52, 104, 156]
• CSF opening pressure [Weeks 26, 52, 104, 156]
• Change From Baseline in Heparan Sulfate Levels in Urinary [Weeks 13, 26, 39, 52, 65, 78, 91, 104, 130, 156]
• Change From Baseline in Dermatan Sulfate Levels in Urinary [Weeks 13, 26, 39, 52, 65, 78, 91, 104, 130, 156]
• Change From Baseline in Heparan Sulfate Levels in Serum [Weeks 13, 26, 39, 52, 65, 78, 91, 104, 130, 156]
• Change From Baseline in Dermatan Sulfate Levels in Serum [Weeks 13, 26, 39, 52, 65, 78, 91, 104, 130, 156]
• Change From Baseline in Liver Volume [Weeks 13, 26, 52, 78, 104, 156]
• Change From Baseline in Spleen Volume. [Weeks 13, 26, 52, 78, 104, 156]
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: Left ventricular posterior wall thickness
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: interventricular septal thickness
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: left ventricular mass index
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: left ventricular ejection fraction
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: left ventricular ejection fraction,
• Change From Baseline in Echocardiography. [Weeks 13, 26, 52, 78, 104, 156]: E/A ratio
• Change From Baseline in 6-minute Walk Test Distance. [Weeks 13, 26, 52, 78, 104, 156]
• Changes from baseline in cognitive age equivalent score of neurocognitive testing [Weeks 52, 104, 156]: Wechsler Intelligence Quotient (IQ) test or the Bayley scales of infant and toddler development
• Changes from baseline in outcome of adaptive behavioral function [Weeks 52, 104, 156]: Vineland adaptive behavior scales
• Changes from baseline in outcome of the Brief Visuospatial Memory Test-Revised [Weeks 13, 26, 52, 78, 104, 130, 156]
• Changes from baseline in outcome of the Hopkins Verbal Learning Test-Revised [Weeks 13, 26, 52, 78, 104, 130, 156]
• Changes from baseline in outcome of the Test of Variables of Attention [Weeks 13, 26, 52, 78, 104, 130, 156]
• Changes from baseline in outcome of the Pediatric Quality of Life Inventory Family Impact Module (PedsQL-FIM) [Weeks 13, 26, 52, 104 156]

Sex: All

Inclusion Criteria:

* Patients who have completed the Part 2 of JR-171-101 study
* A patient from whom written informed consent can be obtained. If the patient is aged under 18 years (20 years in case of Japan) at the time of assent or willingness to participate in the study cannot be confirmed due to MPS I-related intellectual disability, informed permission from the patient's legally acceptable representative (e.g., his/her parents or guardians) need to be obtained instead of his/her consent. Even in this case, written informed consent should be obtained from the patient, wherever possible
* Female patient or male patient whose co-partners is of child-bearing potential agree to use a medically accepted, highly effective method of contraception, such as spermatocidal gel plus condom, an intrauterine device or oral contraceptives until one month after the final administration.

Exclusion Criteria:

* A patient who is unable to perform the study procedures, except for 6-minute walk test, neurocognitive testing, BVMT-R, HVLT-R, and T.O.V.A.
* Judged by the principal investigator or subinvestigator as being unable to undergo lumbar puncture, including those who have difficulties in taking a position for lumbar puncture due to joint contracture or those who are likely to experience difficulty breathing during the lumbar puncture process
* Judged by the principal investigator or subinvestigator to be ineligible to participate in the study due to a history of a serious drug allergy or hypersensitivity to any drugs
* Otherwise judged by the principal investigator or subinvestigator to be ineligible to participate in the study in consideration of patient's safety