Safety, Pharmacokinetics, and Pharmacodynamics/Efficacy of SBC-103 in Mucopolysaccharidosis III, Type B (MPS IIIB)

This study was designed as a 3-part study to evaluate the safety and tolerability of IV
administration of SBC-103. Participants enrolled in Part A (0.3, 1.0, or 3.0 milligrams [mg]
per kilogram [kg] of SBC-103 administered every other week [QOW] for 24 consecutive weeks).
Participants who completed Part A were eligible for Part B (an increase to 1.0 or 3.0 mg/kg
QOW). Participants who completed Part B were eligible for Part C (5.0 and/or 10.0 mg/kg to
continue through Week156; no participants received both 5.0 and 10.0 mg/kg). Due to the early
termination of the SBC-103 development program, including this study, all participants
withdrew from Part C at the sponsor's decision. As a result of the early termination of this
program, this report provides only safety data.

Key Inclusion Criteria:

- A participant was greater than or equal to 2 years of age but less than 12 years of
age at the time of informed consent.

- Definitive diagnosis of MPS IIIB.

- Documented developmental delay.

Key Exclusion Criteria:

- Received treatment with gene therapy at any time.

- Previous hematopoietic stem cell or bone marrow transplant.

- Had any internal or non-removable external metal items that presented a safety risk
for study assessments that utilized magnetic fields, or any other medical condition or
circumstance in which magnetic resonance imaging was contraindicated according to
local institutional policy.

- Known hypersensitivity to eggs.