The Impact of Frequency of Home Phenylalanine Measurements on Metabolic Control in a Population of Patients With Classic Phenylketonuria

Recommendations regarding the frequency of phenylalanine level monitoring lack solid support from evidence derived from prospective randomized trials, including in the adult population with classic PKU. Current recommendations indicate that in adults (excluding the period of pregnancy planning and pregnancy itself), Phe levels should be assessed at least once a month or more frequently if additional indications exist. As part of this study, we plan to obtain, for the first time, high-quality data on the impact of Phe monitoring frequency on Phe control in adults. The primary objective of the study will be to assess the effect of the frequency (once a week versus once a month) of Phe level measurements on the metabolic control of phenylketonuria, as expressed by Phe concentration in DBS, in adult patients with the classic form of phenylketonuria.

Inclusion Criteria: 1. Informed consent to participate in the study 2. Male or female participants aged ≥18 and ≤65 years 3. Clinical diagnosis of classic phenylketonuria (PKU) documented in the medical history by at least 2 measurements of blood phenylalanine concentration ≥600 μmol/l and a predicted PAH enzyme activity \ 900 μmol/L in any measurement taken within 6 months prior to the start of the study 3. Drug or alcohol abuse 4. A person who, in the investigator's opinion, is unable or unwilling to comply with the study requirements. Persons who are legally incapacitated will not be eligible to participate in the study 5. Current participation in another clinical trial or use of any experimental drug within 30 days prior to screening 6. Planning a pregnancy or being pregnant 7. Confirmed diagnosis of primary BH4 deficiency, documented by the presence of pathogenic mutations in both alleles of the following genes: 6-pyroyl-tetrahydrobiopterin synthase, recessive guanosine triphosphate (GTP) cyclohydrolase, sepiapterin reductase, dihydropteridine quinonoid reductase, or pterin 4 alpha-carbinolamine dehydratase 8. Use of sapropterin, sepiapterin, or pegvaliaza concurrently or within 365 days prior to screening