An Extension Study to Determine Safety and Efficacy for Pediatric Patients With MPS Type IIIA Disease Who Participated in Study HGT-SAN-093.

Inclusion Criteria:

Patients must meet all of the following criteria to be considered eligible for enrollment:

1. Patient has completed through at least the Week 48 visit of Study HGT-SAN-093

2. The patient's parent(s) or legally authorized guardian(s) must have voluntarily signed
an Institutional Review Board- (IRB-)/ Independent Ethics Committee- (IEC-) approved
informed consent form after all relevant aspects of the study have been explained and
discussed. Consent of the patient's parent(s) or legally authorized guardian(s) and
the patient's assent, as relevant, must be obtained

Exclusion Criteria:

Patients will be excluded from the study if any of the following criteria are met:

1. The patient, if randomized to treatment in Study HGT-SAN-093, has experienced a
decline of more than 20 points in the BSID-III cognitive DQ score between Baseline and
the Week 48 visit in Study HGT-SAN-093, AND, upon individual evaluation by the
Investigator, has been deemed a treatment failure*

2. The patient has experienced, in the opinion of the Investigator, a safety or medical
issue that contraindicates treatment with HGT-1410, including but not limited to
clinically relevant intracranial hypertension, severe infusion-related reactions after
treatment with HGT-1410, uncontrollable seizure disorder

3. The patient has a known hypersensitivity to any of the components of HGT-1410

4. The patient is enrolled in another clinical study, other than HGT-SAN-093, that
involves clinical investigations or use of any investigational product (drug or
[intrathecal/spinal] device) within 30 days prior to study enrollment or at any time
during the study

5. The patient has any known or suspected hypersensitivity to anesthesia or is thought to
be at an unacceptably high risk for anesthesia due to airway compromise or other
conditions

6. The patient has a condition that is contraindicated as described in the SOPH-A-PORT®
Mini S IDDD Instructions for Use, including:

1. The patient has had, or may have, an allergic reaction to the materials of
construction of the SOPH-A-PORT ® Mini S device

2. The patient's body size is too small to support the size of the SOPH-A-PORT ®
Mini S Access Port, as judged by the Investigator

3. The patient's drug therapy requires substances known to be incompatible with the
materials of construction

4. The patient has a known or suspected local or general infection

5. The patient is at risk of abnormal bleeding due to a medical condition or therapy

6. The patient has one or more spinal abnormalities that could complicate safe
implantation or fixation

7. The patient has a functioning CSF shunt device

8. The patient has shown an intolerance to an implanted device

7. The patient is unable to comply with the protocol (eg, is unable to return for safety
evaluations, or is otherwise unlikely to complete the study) as determined by the
Investigator

- All treated patients in Study HGT-SAN-093 will have their cognitive development
assessed at the Week 48 Visit in Study HGT-SAN-093. If a decline from Baseline of
20 points or less in the BSID-III DQ score is observed, then the patient may
proceed into the Study SHP-610-201 without further evaluation. If a decline from
Baseline of more than 20 points in DQ score is observed, then an individual
evaluation by the Investigator will occur to determine if the patient is a
treatment failure. This individual evaluation will take into account the DQ
scores, VABS-II score, physical status, and any other information available for
that patient at that time. If the Investigator deems the patient to be a
treatment failure, then the patient may not enter the Study SHP-610-201