Conditions: GTP Cyclohydrolase Deficiency
Allocation: NON_RANDOMIZED | Intervention model: SINGLE_GROUP
Enrollment: 12
Healthy volunteers: no

Brief summary:
The purpose of this study is to identify the dose of Kuvan needed to normalize the levels of tetrahydrobiopterin (BH4) in patients with a Guanosine Triphosphate Cyclohydrolase (GTPCH) deficiency and to asses the potential impact of oral Kuvan on mood and function in individuals with GTPCH deficiency who may be experiencing symptoms of anxiety, depression, fatigue, trouble concentrating, or memory loss. This will be a phase one study. The investigators will monitor patients over a period of three to six months while on the medication. Medication levels will be monitored by measuring the BH4 levels in cerebral spinal fluid (CSF). Patients will undergo a baseline lumbar puncture and two follow-up lumbar punctures for this purpose. The investigators will also monitor emotional function and motor function.

Detailed description:

Arms:
arm 1: This cohort will be enrolled first. Analysis will be done to determine the optimum dosing of Kuvan to normalize BH4 levels in the Cerebral Spinal Fluid. This cohort will begin at a dose of 20mg/kg/day. arm 2: Participants in cohort 2 will be enrolled after the analysis of cohort 1 data has taken place. Dosing for cohort 2 will be based on results obtained in cohort 1, but will plan on starting at 30 mg/kg/day.

Interventions: intervention 1: Sapropterin
Intervention descriptions: intervention 1: Sapropterin will be taken daily for 12 or 24 weeks. Starting dose will be 20mg/kg/day and will increase at the 8 week visit to 30 mg/kg/day. Dosing may be further increased to as high as 40 mg/kg/day in attempt to normalize BH4 levels in CSF. Starting dose for Cohort 2 will be determined from data analysis in Cohort 1.

Protocol document: