Long-term Follow-Up for RGX-121

A Long-term Follow-up Study to Evaluate the Safety and Efficacy of RGX-121

RGX-121-5101 is an observational long-term follow-up study to the RGX-121-101 or RGX-121-1102 studies where participants received RGX-121, a gene therapy intended to deliver a functional copy of the iduronate-2-sulfatase gene (IDS) to the central nervous system. This study will evaluate the long-term safety and efficacy of RGX-121.

Study Overview

• Status: Active, not recruiting
• Conditions: Mucopolysaccharidosis II
• Intervention / Treatment: Other: Long-term Follow-Up

Detailed Description

This is a prospective follow-up study to evaluate the long-term safety and efficacy after a single administration of RGX-121. Eligible participants are those who previously have enrolled in clinical study RGX-121-101 or RGX-121-1102 and received a single intracisternal (IC) or intracerebroventricular (ICV) infusion of RGX-121. Enrollment of each participant will occur the same day or after the participant has completed the end of study (EOS) visit or early termination visit (ET) from the previous (parent) study. Participants will be followed in this study cumulatively for up to 5 years after RGX-121 administration (inclusive of the parent study). No treatment will be administered under this observational protocol. The total study duration for each participant may vary depending on when they enroll in the current study following RGX-121 administration in the parent study.

• Study Type: Observational
• Enrollment (Actual): 27

Contacts and Locations

Study Locations

• Brazil
  • Porto Alegre, Brazil, 90035-903
    • Hospital de Clínicas de Porto Alegre
• United States
  • California
    • San Francisco, California, United States, 94158
      • University of California, San Francisco (UCSF)- Benioff Children's Hospital
  • New Jersey
    • New Brunswich, New Jersey, United States, 08901
      • Saint Peter's Healthcare System
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19104
      • The Children's Hospital of Philadelphia (CHOP)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 2 years and older (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Up to 54 subjects who have received RGX-121 in a previous parent study.

Description

Inclusion Criteria:

• To be eligible, a participant must have previously received RGX-121 in a separate parent trial.
• Participant or participant's legal guardian(s) is/(are) willing and able to provide written, signed informed consent

Exclusion Criteria:

• Participant has not received RGX-121 previously in a separate parent trial.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Long-term Follow-Up; No intervention.	Other: Long-term Follow-Up; No intervention

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Long-term Safety of RGX-121	To evaluate the safety of RGX-121 serious and adverse events as assessed by Common Terminology Criteria for Adverse Events (CTCAE Version 5.0).	5 years inclusive of parent study

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the long-term effect of RGX-121 on neurodevelopmental parameters of cognitive, motor, behavioral, and adaptive function (Bayley Scales of Infant and Toddler Development, 3rd Edition)	To evaluate the long-term effect of RGX-121 on neurodevelopmental parameters as measured by the BSID-III. The BSID-III assesses children aged 1 to 42 months across several domains (cognitive, language, and motor domains) to give a holistic view of the participants' development and potential delays.	5 years inclusive of parent study
Evaluate the long-term effect of RGX-121 on neurodevelopmental parameters of cognitive, motor, behavioral, and adaptive function (Kaufman Assessment Battery for Children, 2nd Edition)	To evaluate the long-term effect of RGX-121 on neurodevelopmental parameters as measured by the KABC-II. The KABC-II is an individually administered measure of the cognitive processing abilities of children and adolescents aged 3 through 18.	5 years inclusive of parent study
Evaluate the long-term effect of RGX-121 on neurodevelopmental parameters of cognitive, motor, behavioral, and adaptive function (Mullen Scales of Early Learning)	To evaluate the long-term effect of RGX-121 on neurodevelopmental parameters as measured by the MSEL. The MSEL is a standardized developmentally integrated system that assesses language, motor, and perceptual abilities, and measures cognitive ability and motor development.	5 years inclusive of parent study
Evaluate the long-term effect of RGX-121 on neurodevelopmental parameters of cognitive, motor, behavioral, and adaptive function (Vineland Adaptive Behavior Scales, 2nd Edition)	To evaluate the long-term effects of RGX-121 on neurodevelopmental parameters as measured by the VABS-II. The VABS-II assesses adaptive behavior in individuals from infancy to age 90 years. The VABS-II offers a way to measure personal and social self-sufficiency in real-life situations and to observe how these cognitive abilities impact the autonomy management process when put into practice	5 years inclusive of parent study
Evaluate the long-term impact of RGX-121 on Plasma Biomarkers (I2S)	To evaluate the long-term impact of RGX-121 on Plasma biomarker Iduronate-2-sulfatase (I2S) through plasma collection for participants not receiving ERT (discontinued or naïve).	5 years inclusive of parent study
Evaluate the long-term impact of RGX-121 on CSF Biomarkers (I2S)	To evaluate the long-term impact of RGX-121 on CSF Biomarker Iduronate-2-sulfatase (I2S) through lumbar puncture.	5 years inclusive of parent study
Evaluate the long-term impact of RGX-121 on CSF Biomarkers (GAGs)	To evaluate long-term impact of RGX-121 on CSF Biomarker Glycosaminoglycans (GAGs) through lumbar puncture.	5 years inclusive of parent study
Long-term effect of RGX-121 on Urine Biomarker (GAGs)	To evaluate the long-term impact of RGX-121 on Urine Biomarker Glycosaminoglycans (GAGs) through urine analysis.	5 years inclusive of parent study

Collaborators and Investigators

• Sponsor: REGENXBIO Inc.

Study record dates

Study Major Dates

• Study Start (Actual): March 14, 2021
• Primary Completion (Estimated): October 1, 2028
• Study Completion (Estimated): October 1, 2028

Study Registration Dates

• First Submitted: October 15, 2020
• First Submitted That Met QC Criteria: October 15, 2020
• First Posted (Actual): October 22, 2020

Study Record Updates

• Last Update Posted (Actual): August 19, 2026
• Last Update Submitted That Met QC Criteria: August 17, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Gene Therapy; MPS II; Hunter
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Pathologic Processes; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Connective Tissue Diseases; Neurobehavioral Manifestations; Death; Heredodegenerative Disorders, Nervous System; Intellectual Disability; Genetic Diseases, X-Linked; Carbohydrate Metabolism, Inborn Errors; Lysosomal Storage Diseases; Mucinoses; Death, Sudden; Mucopolysaccharidoses; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Skin and Connective Tissue Diseases; X-Linked Intellectual Disability; Infant Death; Mucopolysaccharidosis II; Sudden Infant Death
• Other Study ID Numbers: RGX-121-5101

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No