This study will evaluate the safety and tolerability of RGX-111 in patients with Mucopolysaccharidosis Type I with a neurocognitive deficit that are at least 4 months old. This study involves administration of the RGX-111, general anesthesia, lumbar puncture, blood draws, MRI, ultrasound, electrocardiogram, echocardiogram, hearing test, and chart review.

The purpose of this study is to look at the safety and tolerability of RBX-121, a one-time gene therapy, in subjects with MPS II (Hunter Syndrome). You may be eligible for this study if you are a male between the ages of 4 months to 5 years old. Reimbursement for travel and research procedures will be provided. This study involves blood draws, interviews, urine collection, genetic testing, general anesthesia, lumbar punctures, MRI, gene therapy, lumbar puncture, ultrasound, ECG/echocardiogram and physical and neurological examinations. If you have questions or would like to learn more about the study, please contact the study team at MetabolismResearch@email.chop.edu.

New medicines are being developed to treat urea cycle disorders. To better understand if the medicines help restore how the urea cycle works, doctors and researchers need a safe and accurate test to measure how well the urea cycle is working. One way to measure how the urea cycle works is to drink a very small amount of a "labeled" form of ammonia called 15N-ammonium chloride (15NH4Cl). 15NH4Cl will be referred to as "the tracer", this tracer is non-radioactive. We can follow the tracer in blood tests to measure how the body uses and removes ammonia in the urea cycle. The amount of tracer detected in the blood may indicate if the urea cycle is working correctly.

The goal of this study is to use the tracer to measure how well the urea cycle works in both healthy participants and participants with urea cycle disorders.