An Open-label Phase I/II Study of JR-446 in Mucopolysaccharidosis Type IIIB

Inclusion Criteria:

• Chronological age of <18 years

• Confirmed diagnosis of MPS IIIB

Exclusion Criteria:

• Prior experience to gene therapy or HSCT with successful engraftment

• Past use of another investigational drug or product in last 4 months or 5 half-lives (whichever is longer) before signing ICF

• Current participation in a clinical trial or past participation (within 30 days ofenrolment into this study) in a study involving invasive procedures

• Past use of Genistein or Kineret (anakinra) within 4 months before signing ICF

• Serious drug allergy or hypersensitivity

• Contraindication for lumbar puncture or MRI

• History of bleeding disorder or current use of medications that, in the opinion ofthe investigator, place them at risk of bleeding following lumbar puncture

The above information is not intended to contain all considerations relevant to a patient's potential participation in this clinical trial.