Conditions: Phenylketonuria (PKU)
Allocation: NON_RANDOMIZED | Intervention model: PARALLEL
Enrollment: 6
Healthy volunteers: yes

Brief summary:
This self-controlled, prospective, pilot study is designed to gather information regarding the diurnal variation (changes that occur each day) in the levels of plasma phenylalanine (Phe) and tyrosine in patients with phenylketonuria (PKU) and in the non-PKU population.

Detailed description:
Phenylketonuria (PKU) is a rare genetic metabolic disease caused by a mutation that codes for an enzyme that converts the essential amino acid phenylalanine (Phe) into tyrosine. An absence or deficiency of this enzyme activity results in a Phe elevation, where higher Phe levels result in neurological damage. Diurnal variations of Phe levels have been observed in PKU patients in a 24-hour period.

As Kuvan has shown to stabilize Phe levels in PKU patients over time, our hypothesis is that this can be demonstrated within a 24-hour period of observation and indicate therefore that Kuvan may correlate with a lower plasma Phe variability. This study on PKU patients' diurnal variation will also provide important information as to the current method of blood Phe monitoring in a clinical setting to learn more about the optimal way to measure Phe concentration.

The study will last about 4 weeks (6 study visits) for the PKU participants and about 1 week (2 study visits) for the control group.

Participants will be required to follow a recommended diet, complete a dietary log, and undergo several blood draws, including a 24-Hour Blood Assessment in which blood will be obtained 8 times throughout the day.

Arms:
arm 1: * Subjects will be administered Kuvan once daily.
* They will undergo several blood draws, including a 24-Hour Blood Assessment (at Study Visit #2 before the commencement of Kuvan), plasma Phe/Tyr draws (at Study Visits #3, 4, and 5), and another 24-Hour Blood Assessment (at Study Visit #6). arm 2: * Subjects allocated into this group will be healthy, non-PKU individuals that may be a relative (ex: sibling) of a PKU participant, but they don't have to be a blood relation.
* These subjects will undergo a 24-Hour Blood Assessment (at Study Visit #2).

Interventions: intervention 1: Kuvan
Intervention descriptions: intervention 1: Only PKU participants (Arm 1) will be administered Kuvan once daily either at a dose of 20 mg/kg/day (if the PKU participant is not currently taking Kuvan) or at the subject's regular dose (if the PKU participant is currently taking Kuvan). They will remain on Kuvan for 4 weeks.

Protocol document: