Study of UX003 Recombinant Human Beta-Glucuronidase (rhGUS) Enzyme Replacement Treatment in Mucopolysaccharidosis Type 7, Sly Syndrome (MPS 7) Patients Less Than 5 Years of Age

Adverse event (AE): any untoward medical occurrence in a participant, whether or not considered drug related. Serious AE (SAE): an AE or suspected adverse reaction that at any dose results in any of the following outcomes: death; a life-threatening AE; inpatient hospitalization or prolongation of existing hospitalization; persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions; a congenital anomaly/birth defect. Other important medical events may also, in the opinion of the Investigator, be considered SAEs. An AE was considered a TEAE if it occurred on or after the first dose, and was not present prior to the first dose, or it was present at the first dose but increased in severity during the study. Events recorded as either possibly, probably, or definitely related to treatment were categorized as related. AE severity was graded using the National Cancer Institute's Common Terminology Criteria for Adverse Events, Version 4.03.

Time frame: From first dose of study drug until 30 days after the last dose of study drug. Mean (SD) treatment duration was 98.11 (29.02) weeks

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study.

Liquid chromatography-mass spectrometry/mass spectrometry-dermatan sulfate (LS-MS/MS-DS) method. For the participant previously treated with UX003 under an eIND, percent change from initial baseline was used.

Time frame: Baseline (Week 0), Week 48

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study and had a non-missing baseline and Week 48 assessment.

For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

The Z-score indicates the number of standard deviations away from a reference population (from the CDC growth charts) in the same age range and with the same sex. A Z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z-scores indicate a better outcome. For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 36, 48

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 48, 96, 144

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 48, 96, 144

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

The Z-score indicates the number of standard deviations away from a reference population (from the CDC growth charts) in the same age range and with the same sex. A Z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z-scores indicate a better outcome. For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

For all participants (including the participant previously treated with UX003 under an eIND), the last non-missing study assessment prior to the first dose in this study was used as baseline.

Time frame: Baseline, Weeks 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with a non-missing assessment at baseline and given time point.

The Z-score indicates the number of standard deviations away from a reference population (based on Tanner's standard \[Tanner et al. 1985\]) in the same age range and with the same sex. A Z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z-scores indicate a better outcome. The growth velocity for pre-treatment is based on standing height within 2 years prior to treatment. The growth velocity for post-treatment is based on all standing height data during the study period. For the participant previously treated with UX003 under an eIND, the growth velocity was calculated for pre initial UX003 treatment and post initial UX003 treatment.

Time frame: Pre-treatment (based on standing height within 2 years prior to treatment), Post-treatment (based on all standing height data during the study period up to Week 48)

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with both historical pre-treatment (within 2 years) and post-treatment data. Growth velocity Z-score was only calculated for participants ≥ 2.25 years.

The growth velocity for pre-treatment is based on standing height within 2 years prior to treatment. The growth velocity for post-treatment is based on all standing height data during the study period. For the participant previously treated with UX003 under an eIND, the growth velocity was calculated for pre initial UX003 treatment and post initial UX003 treatment.

Time frame: Pre-treatment (based on standing height within 2 years prior to treatment), Post-treatment (based on all standing height data during the study period up to 240 weeks)

Population: Full analysis set: all enrolled participants who received at least one dose of UX003 during the study with both historical pre-treatment (within 2 years) and post-treatment data.