Clinical Research Directory

A Clinical Study of Glycerol Phenylbutyrate in Chinese Patients With Urea Cycle Disorders

Urea cycle disorders (UCD) are rare diseases in China, would lead to high mortality and disability, which require long-term management due to the recurrent symptoms. This multi-center, prospective, single-arm study was designed to assess the efficacy and safety of Glycerol Phenylbutyrate for Chinese pediatric patients with UCD, to provide the additional references and treatment options for Chinese UCD patients, and enhance the clinical management of UCD in China. This study primarily observes patients with UCD who are on long-term treatment with glyceryl phenylbutyrate, the total planned observation period is 5 years.

Ureagenesis Analysis in Healthy Subjects and in Urea Cycle Disorder Patients

Urea cycle disorders (UCDs) are dramatic congenital inherited metabolic disorders. There is no cure. Many novel therapeutic approaches are currently being developed, which hopefully will change the current situation. Testing the efficacy of such new therapies in patients is a challenge, because many clinical parameters are influenced by several disturbances and biochemical parameters are often not very specific. The measurement of ureagenesis is a tool to analyze the entire function of the urea cycle in a single test. This is more meaningful for the characterization of UCD patients than the analysis of single metabolites or enzymes. Therefore, the test will be important to evaluate current and future novel therapies. The term "ureagenesis" means "production of urea", which is the main task of the urea cycle. This total urea production can be measured with a "tracer" (in this case a stable ammonium chloride isotope). This tracer is non-radioactive and non-toxic. It is for example used as an unmarked substance in cough syrup, diuretic drugs and as food additive. Thus, the tracer does not pose a risk to the participant, especially since only a very low dose is applied. The investigators will analyze specific substances from the urea cycle (namely \[15N, 14N\] urea and several \[15N\] amino acids) that are produced during the test and compare them with results from healthy people. Venous and capillary blood will be sampled at 15 to 30 minutes intervals up to 2 hours after administration of the stable isotope tracer. The maximum test duration is 5 hours. This project is being carried out at one site, namely the University Children's Hospital in Zurich. This project is being carried out under Swiss law. The responsible Ethics Committee has reviewed and approved the study.

At Home Ammonia Monitoring of Inborn Errors of Ammonia Metabolism

The goal of this observational study is to learn if people with certain ammonia metabolism disorders will measure their ammonia levels at home. The main question it aims to answer is: • Will participants measure their ammonia every day? Participants will be asked to: * Attend three in-person study visits at the clinic. * Measure temperature, heart rate, and blood oxygen every day. * Complete a short survey every day. * Measure ammonia every day.

Neuroimaging and Neuropsychological Outcomes in Urea Cycle Disorders

In proximal urea cycle disorders (UCD), particularly ornithine transcarbamylase deficiency (OTCD), hyperammonemia (HA) causes increased brain glutamine (Gln) which perturbation is thought to be at the core of the neurological injury. In contrast, in distal UCD such as citrullinemia (argininosuccinate synthetase deficiency; (ASSD) and argininosuccinic aciduria (argininosuccinate lyase deficiency); (ASLD) cognitive impairment and neuropsychiatric disease are common even in the absence of acute HA. As a consequence, both citrulline and argininosuccinate (ASA) or their metabolic products have been implicated as neurotoxic. In this project the investigators will use state-of- the-art neuroimaging and neuropsychological methods to investigate whether patients with OTCD have chronically elevated brain Gln and reduced myo-inositol (mI) levels that correlate with regional brain structural abnormalities and neurocognitive dysfunction. The researchers will further investigate whether during an acute episode of HA elevated brain Gln and decreased mI levels correlate with the magnitude of cytotoxic edema and whether a Gln/mI ratio threshold can be identified at which the cytotoxic edema is followed by cell loss. Finally, the researchers will investigate whether regions of brain damage in ASSD and/or ASLD are distinct from those in OTCD and compare brain Gln levels in ASSD and ASLD in the absence of HA to those in OTCD. The investigators will also seek to determine if brain citrulline and ASA can be identified in the brains of patients with distal UCD and whether they correlate with brain abnormalities seen in MRI and neuropsychological testing. This project will elucidate the chronology of brain pathology both in acute hyperammonemia and chronic UCD and whether, proximal and distal UCD differ in their pathophysiology of brain damage.

Longitudinal Study of Urea Cycle Disorders

Urea cycle disorders (UCD) are a group of rare inherited metabolism disorders. Infants and children with UCD commonly experience episodes of vomiting, lethargy, and coma. The purpose of this study is to perform a long-term analysis of a large group of individuals with various UCDs. The study will focus on the natural history, disease progression, treatment, and outcome of individuals with UCD.