Please assess the completion status of the following clinical trial:

Trial Title: Phenylalanine and Its Impact on Cognition

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: CROSSOVER
- Observational Model: None
- Primary Purpose: SUPPORTIVE_CARE
- Time Perspective: None
- Masking: DOUBLE
- Phase: PHASE4
- Number of Arms: 2.0

Eligibility Criteria:
PATIENTS~Inclusion Criteria:~* PKU diagnosed after a positive newborn screening~* Treatment with Phe-restricted diet starting within the first 30 days of life~* Age ≥18 years~* Capable of following the study design~* Written informed consent~Exclusion Criteria:~* Patients with PKU not following a Phe-restricted diet within 6 months before the study~* Phe concentration above 1600 µmol/L within 6 months before the study~* Concomitant disease states suspected to significantly affect primary or secondary outcomes, e. g. untreated vitamin B12 deficiency~* Known or suspected non-compliance, drug or alcohol abuse~* Change in medications likely to significantly interfere with cognitive function testing~* Known or suspected hypersensitivity or allergy to one of the ingredients of the placebo~* Women who are pregnant or intent to get pregnant during the course of the study or who are breast feeding~* Female participants of childbearing potential, not using and not willing to continue using one (or more) highly efficient (Pearl index less than 1) method of contraception for the entire study duration.~* Inability to follow the procedures of the study, e. g. due to language problems (lack of fluency in German or French), psychological disorders, dementia, etc. of the participant.~* Participation in another interventional study within the 30 days preceding and during the present study.~* Previous enrolment into the current study~* Conditions interfering with MRI such as magnetic (metallic) particles in the skull or brain, cardiac pacemaker, deep brain stimulators, cochlear implant, braces or permanent retainers~HEALTHY CONTROLS~Inclusion Criteria:~* Age ≥18 years~* Comparable to patients with regard to age, gender and educational level~* Capable of following the study design~* Written informed consent~Exclusion Criteria:~* Known or suspected drug or alcohol abuse~* Change in medications likely to significantly interfere with cognitive function testing~* Women who are pregnant or intent to get pregnant during the course of the study or who are breast feeding~* Inability to follow the procedures of the study, e. g. due to language problems (lack of fluency in German or French), psychological disorders, dementia, etc. of the participant.~* Participation in another interventional study within the 30 days preceding and during the present study.~* Previous enrolment into the current study~* Conditions interfering with MRI such as magnetic (metallic) particles in the skull or brain, cardiac pacemaker, deep brain stimulators, cochlear implant, braces or permanent retainers

- Gender: ALL
- Minimum Age: 18 Years
- Maximum Age: None
- Healthy Volunteers: t

Study Arms:
- Phenylalanine (Type: EXPERIMENTAL): Capsules containing 250 mg Phenylalanine (Phe). The daily dose will be chosen according to gender and weight at the time of T1 and will be divided in 3 separate doses. The assigned dose of the IMP will be kept throughout the whole study and weight fluctuations will not be considered.~Female~\<60 kg: 1500 mg per day (divided in 3 doses): 250 mg 2-2-2-0~≥60 kg: 2000 mg per day (divided in 3 doses): 250 mg 2-2-4-0~Male~\<60 kg: 2500 mg per day (divided in 3 doses): 250 mg 4-2-4-0~≥60 kg: 3000 mg per day (divided in 3 doses): 250 mg 4-4-4-0~Phe capsules can be ingested before, during or after a meal or together with other amino acid supplements. The last capsule of the given intervention period will be timed to be ingested with the last meal before the study visit.~Patients will take Phe for 4 weeks.
- Placebo (Type: PLACEBO_COMPARATOR): Capsules containing 250mg Placebo. Placebo capsules will be administered in identical manner to Phe capsules.~Patients will take the Placebo for 4 weeks.

Based on this trial design, predict the completion outcome and termination type (if applicable).