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Tetrahydrobiopterin (BH 4) is the natural cofactor of aromatic amino acid hydroxylases and essential for degradation of phenylalanine and synthesis of catecholamines and serotonin. It can be synthesized either de novo from GTP or through the salvage pathway from sepiapterin. Sepiapterin, a natural precursor of BH 4 , is a more stable molecule and is transported more efficiently across cellular membranes, thus having potentially significant advantage over BH 4 as a pharmacological agent for diseases associated with BH 4 -deficient conditions. We report the results of a first-in-humans, randomized, double-blind, placebo-controlled, dose-ranging, Phase I clinical trial in 83 healthy volunteers of CNSA-001, a novel formulation of sepiapterin. Single oral doses of 2.5–80 mg/kg CNSA-001 caused dose-related increases in plasma sepiapterin (mean C max 0.58–2.92 ng/mL) and BH 4 (mean C max 57–312 ng/mL). Maximum plasma concentrations were achieved in about 1–2 h (sepiapterin) or about 4 h (BH 4) after CNSA-001 oral intake. Increases in plasma BH 4 were substantially larger in absolute terms and on a dose-for-dose basis following treatment with CNSA-001 vs. sapropterin dihydrochloride, a synthetic form of BH 4. The pharmacokinetics of plasma sepiapterin and BH 4 were similar before and after seven days of repeat daily dosing with CNSA-001 at 5, 20 or 60 mg/kg indicating little or no drug accumulation. Oral administration of CNSA-001 resulted in higher concentrations of sepiapterin in fasted vs. fed subjects, but overall BH 4 plasma exposure following CNSA-001 intake increased by 1.7–1.8-fold in fed subjects. CNSA-001 was well tolerated, with no clear dose-relationship for adverse events (AE), no serious AE and no study discontinuations for AE. These data indicate that CNSA-001 is rapidly and efficiently converted to BH 4 in humans supporting further clinical evaluation of CNSA-001 for the management of PKU, primary BH 4 deficiencies and other diseases associated with deficient BH 4 metabolism. [ABSTRACT FROM AUTHOR]

Objective: In May 2018, the US Food and Drug Administration approved pegvaliase-pqpz (Palynziq*), the first enzyme substitution therapy for the treatment of phenylketonuria (PKU). This article provides an overview of the mechanism of action, pharmacokinetic properties, clinical efficacy, and the safety and tolerability profile of pegvaliase.Methods: Relevant information was identified through a comprehensive literature search of several databases using the keywords pegvaliase, rAvPAL-PEG, and phenylketonuria. Additional information was gathered from the pegvaliase package insert, posters presented at scientific meetings, and materials provided from the manufacturer, BioMarin.Results: Pegvaliase is effective in decreasing blood phenylalanine levels, and is associated with a manageable side-effect profile. Phase III clinical trial data demonstrated that 60.7% of patients were able to achieve blood phenylalanine levels less than the guideline recommended 360 µmol/L at 24 months. Brief sub-studies also showed the improvement in inattention symptoms in patients treated with pegvaliase, compared to placebo.Conclusion: Pegvaliase is a promising new treatment option for adults living with PKU. Further studies are warranted to determine long-term safety and clinical efficacy in sub-populations. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is a genetic disorder caused by variants in the gene encoding phenylalanine hydroxylase (PAH), resulting in accumulation of phenylalanine to neurotoxic levels. Here, we analyzed the cellular stability, localization, and interaction with wild‐type PAH of 20 selected PKU‐linked PAH protein missense variants. Several were present at reduced levels in human cells, and the levels increased in the presence of a proteasome inhibitor, indicating that proteins are proteasome targets. We found that all the tested PAH variants retained their ability to associate with wild‐type PAH, and none formed aggregates, suggesting that they are only mildly destabilized in structure. In all cases, PAH variants were stabilized by the cofactor tetrahydrobiopterin (BH4), a molecule known to alleviate symptoms in certain PKU patients. Biophysical calculations on all possible single‐site missense variants using the full‐length structure of PAH revealed a strong correlation between the predicted protein stability and the observed stability in cells. This observation rationalizes previously observed correlations between predicted loss of protein destabilization and disease severity, a correlation that we also observed using new calculations. We thus propose that many disease‐linked PAH variants are structurally destabilized, which in turn leads to proteasomal degradation and insufficient amounts of cellular PAH protein. Phenylketonuria (PKU) is an autosomal recessive genetic disorder caused by variants in the gene encoding phenylalanine hydroxylase (PAH). Here it is shown that several disease‐linked variants of the PAH protein are structurally destabilized and degraded by the proteasome. These destabilized PAH variants can be identified by in silico structure‐based energy calculations. [ABSTRACT FROM AUTHOR]

Abstract Phenylketonuria remains one of the most common inborn errors of metabolism. In the UK it is detected on the newborn heel-prick screening sample allowing early treatment with a strict low phenylalanine diet supplemented with artificial amino acids and appropriate vitamin and minerals. Although the long-term prognosis is good, there is an increasing body of evidence highlighting subtle problems in neuropsychological function with slower reaction times and poorer executive function than peers. White matter changes clearly seen on brain magnetic resonance imaging may have some relationship to these neuropsychological difficulties but their significance is not clearly understood. The diet, although successful, is difficult to follow lifelong and with its attendant risks of nutritional deficiencies needs careful specialist management. In view of these challenges new treatments such as sapropterin (a tetrahydrobiopterin analogue) and large neutral amino acids are currently being used in phenylketonuria and clinical trials are underway using ammonia lyase as enzyme replacement therapy. Maternal phenylketonuria syndrome remains a risk for those who conceive whilst blood phenylalanine is elevated and females must be counselled early in childhood to avoid this risk. [ABSTRACT FROM AUTHOR]

Background: Hyperphenylalaninemia is a hereditary metabolic disorder that causes elevated blood phenylalanine (Phe). Hyperphenylalaninemias are classified as Phenylketonuria PKU (Phe > 6 mg/dL) or mild hyperphenylalaninemia (mHPA) (Phe 2–6 mg/dL). This study examines the cognitive functioning of early diagnosed children with mHPA compared with early diagnosed and treated children with PKU. Sample and methods: Psychomotor development (BSID-II) at 12 and 36 months of age, and cognitive performance at 4 and 7 years of age (WPPSI and WISC-R), were assessed in 118 PKU and 97 mHPA patients. Cognitive profile analysis of WISC-R subscales in school age children was performed and results were compared between the two groups. Results: Both groups preformed within the average range. Scores were significantly higher in the mHPA group. The mean Mental Development Index (MDI) at 12 months of age was 98.1 in the mHPA group and 92.3 in the PKU group (p

Background: In phenylketonuria, dietary treatment prevents most of the severe brain disease. However, patients have to follow a diet restricted in several natural components, what may cause decreased bone density and obesity. Exercise is known to improve both mental functioning and bone density also avoiding obesity, and could optimize aspects of central and peripheral outcome, regardless changes in phenylalanine (Phe) levels. However, the acute effects of exercise on metabolic parameters in phenylketonuria patients are unknown and thereby long-term adaptations are unclear. Therefore, this study aimed to evaluate patients' basal metabolic rate (BMR), and their acute response to an aerobic exercise session on plasma concentrations of Phe, tyrosine (Tyr), and branched-chain amino acids (BCAA), as well as metabolic and hormonal responses. Methods: Five early- and four late diagnosed phenylketonuria patients aged 21 ± 4 years and 17 sex-, age-, and BMI-matched controls were evaluated for BMR, peak oxygen consumption (VO2peak) and plasma amino acid, glucose, lipid profile and hormonal levels. At least one week later, participants performed a 30-min aerobic exercise session (intensities individually calculated using the VO2peak results). Blood samples were collected in fasted state (moment 1, M1) and immediately after a small breakfast, which included the metabolic formula for patients but not for controls, and the exercise session (moment 2, M2). Results: Phenylketonuria patients and controls showed similar BMR and physical capacities. At M1, patients presented higher Phe concentration and Phe/Tyr ratio; and lower levels of BCAA and total cholesterol than controls. Besides that, poorly controlled patients tended to stay slightly below the prescribed VO2 during exercise. Both patients and controls showed increased levels of total cholesterol and LDL at M2 compared with M1. Only controls showed increased levels of Tyr, lactate, and HDL; and decreased Phe/Tyr ratio and glucose levels at M2 compared to values at M1. Conclusions: Acute aerobic exercise followed by a Phe-restricted breakfast did not change Phe concentrations in treated phenylketonuria patients, but it was associated with decreased Phe/Tyr only in controls. Further studies are necessary to confirm our results in a higher number of patients.

We aimed to assess if the same cognitive batteries can be used cross-nationally to monitor the effect of Phenylketonuria (PKU). We assessed whether a battery, previously used with English adults with PKU (AwPKU), was also sensitive to impairments in Italian AwPKU. From our original battery, we selected a number of tasks that comprehensively assessed visual attention, visuo-motor coordination, executive functions (particularly, reasoning, planning, and monitoring), sustained attention, and verbal and visual memory and learning. When verbal stimuli/or responses were involved, stimuli were closely matched between the two languages for psycholinguistic variables. We administered the tasks to 19 Italian AwPKU and 19 Italian matched controls and compared results from with 19 English AwPKU and 19 English matched controls selected from a previously tested cohort. Participant election was blind to cognitive performance and metabolic control, but participants were closely matched for age and education. The Italian AwPKU group had slightly worse metabolic control but showed levels of performance and patterns of impairment similar to the English AwPKU group. The Italian results also showed extensive correlations between adult cognitive measures and metabolic measures across the life span, both in terms of Phenylalanine (Phe) levels and Phe fluctuations, replicating previous results in English. These results suggest that batteries with the same and/or matched tasks can be used to assess cognitive outcomes across countries allowing results to be compared and accrued. Future studies should explore potential differences in metabolic control across countries to understand what variables make metabolic control easier to achieve.

The nutritional composition of special low protein foods (SLPFs) is controlled under EU legislation for ‘Foods for Special Medical Purposes (FSMP)’. They are designed to meet the energy needs of patients unable to eat a normal protein containing diet. In phenylketonuria (PKU), the macronutrient contribution of SLPFs has been inadequately examined. Aim: A 3-year longitudinal prospective study investigating the contribution of SLPFs to the macronutrient intake of children with early treated PKU. Methods: 48 children (27 boys) with a mean recruitment age of 9.3 y were studied. Semi-quantitative dietary assessments and food frequency questionnaires (FFQ) were collected three to four times/year for 3 years. Results: The mean energy intake provided by SLPFs was 33% (SD ± 8), and this figure was 42% (SD ± 13) for normal food and 21% (SD ± 5) for protein substitutes (PS). SLPFs supplied a mean intake of 40% carbohydrate (SD ± 10), 51% starch (SD ± 18), 21% sugar (SD ± 8), and 38% fat (SD ± 13). Fibre intake met 83% of the Scientific Advisory Committee on Nutrition (SACN) reference value, with 50% coming from SLPFs with added gums and hydrocolloids. Low protein bread, pasta and milk provided the highest energy contribution, and the intake of sweet SLPFs (e.g., biscuits, cakes, and chocolate) was minimal. Children averaged three portions fruit/vegetable daily, and children aged ≥ 12 y had irregular meal patterns. Conclusion: SLPFs provide essential energy in phenylalanine restricted diets. Optimising the nutritional quality of SLPFs deserves more attention.

Protein is the most satiating macronutrient, increasing secretion of gastrointestinal hormones and diet induced thermogenesis. In phenylketonuria (PKU), natural protein is restricted with approximately 80% of intake supplied by a synthetic protein source, which may alter satiety response. Casein glycomacropeptide (CGMP-AA), a carbohydrate containing peptide and alternative protein substitute to amino acids (AA), may enhance satiety mediated by its bioactive properties. Aim: In a three-year longitudinal; prospective study, the effect of AA and two different amounts of CGMP-AA (CGMP-AA only (CGMP100) and a combination of CGMP-AA and AA (CGMP50) on satiety, weight and body mass index (BMI) were compared. Methods: 48 children with PKU completed the study. Median ages of children were: CGMP100; (n = 13), 9.2 years; CGMP50; (n = 16), 7.3 years; and AA (n = 19), 11.1 years. Semi-quantitative dietary assessments and anthropometry (weight, height and BMI) were measured every three months. Results: The macronutrient contribution to total energy intake from protein, carbohydrate and fat was similar across the groups. Adjusting for age and gender, no differences in energy intake, weight, BMI, incidence of overweight or obesity was apparent between the groups. Conclusion: In this three-year longitudinal study, there was no indication to support a relationship between CGMP and satiety, as evidenced by decreased energy intake, thereby preventing overweight or obesity. Satiety is a complex multi-system process that is not fully understood.

In Phenylketonuria (PKU), the peptide structure of the protein substitute (PS), casein glycomacropeptide (CGMP), is supplemented with amino acids (CGMP-AA). CGMP may slow the rate of amino acid (AA) absorption compared with traditional phenylalanine-free amino acids (Phe-free AA), which may improve nitrogen utilization, decrease urea production, and alter insulin response. Aim: In children with PKU, to compare pre and postprandial AA concentrations when taking one of three PS’s: Phe-free AA, CGMP-AA 1 or 2. Methods: 43 children (24 boys, 19 girls), median age 9 years (range 5–16 years) were studied; 11 took CGMP-AA1, 18 CGMP-AA2, and 14 Phe-free AA. Early morning fasting pre and 2 h postprandial blood samples were collected for quantitative AA on one occasion. A breakfast with allocated 20 g protein equivalent from PS was given post fasting blood sample. Results: There was a significant increase in postprandial AA for all individual AAs with all three PS. Postprandial AA histidine (p < 0.001), leucine (p < 0.001), and tyrosine (p < 0.001) were higher in CGMP-AA2 than CGMP-AA1, and leucine (p < 0.001), threonine (p < 0.001), and tyrosine (p = 0.003) higher in GCMP-AA2 than Phe-free AA. This was reflective of the AA composition of the three different PS’s. Conclusions: In PKU, the AA composition of CGMP-AA influences 2 h postprandial AA composition, suggesting that a PS derived from CGMP-AA may be absorbed similarly to Phe-free AA, but this requires further investigation.

The story of phenylketonuria (PKU) started in 1934 with Asbjørn Følling’s examination of two mentally retarded siblings from a Norwegian family. However, if their mother had not been so persistent in her search for somebody who could give her a reason why both her children were retarded, Asbjørn Følling’s name might never have been associated with PKU and surely the history of PKU would have started differently. In the short review below, the authors give a partly personal and therefore rare account of the early history of PKU, its treatment and the start of neonatal screening. Prof. Woolf is a pioneer of both the dietary treatment of PKU and neonatal screening; Mr. Adams is a long-time advocate for PKU patient interests.

This work was aimed at the definition of a chromatographic method able to separate and quantify impurities present in sapropterin-containing drugs during an accelerated stability study. The chromatographic method was applied to the orphan drug Kuvan® and to its corresponding generic sapropterin Dipharma (Diterin®), both of which are approved for the treatment of hyperphenylalaninemia-induced symptoms. The two products tested had a similar manufacture date and both had an approved stability shelf-life of three years. Samples were analyzed by HPLC at T = 0 and after six months of storage at 40 °C and 75% relative humidity. Identification of the impurities was supported by a detailed mass spectrometry and MS/MS profile. The analysis demonstrated an overall higher stability for the Diterin® formulation, which was related to a lower increase of some impurities compared to Kuvan®.

Objective(s):Phenylketonuria (PKU) is a genetic inborn error of phenylalanine (Phe) metabolism resulting from insufficiency in the hepatic enzyme, phenylalanine hydroxylase (PAH), which leads to elevated levels of Phe in the blood. The present study was carried out for mutation analysis of the PAH gene in West Azerbaijan province of Iran. Materials and Methods:A total of 218 alleles from 40 PKU families were studied using restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) method. Results:The frequencies of IVS10-11, S67P, R261Q, R252W, IVS11nt-1 g>c, R408Q, and Q232Q mutations were 28(35), 17(21.25), 15(18.75), 3(3.75), 3(3.75), 2(2.5), and 1(1.25), in cases group, and 51(23.4), 31(14.2), 27(12.4), 6(2.75), 6(2.75), 4(1.83), and 2(0.92) in total group, respectively. The mutations of R243Q, 364delG, L333F, 261X, I65T, and R408W were not detected in our samples. Conclusion: It can be concluded that the IVS10-11 mutation has the highest frequency in the tested population. To our knowledge, this report is the first in its own kind and provides better understanding of the genetic heterogeneity, the origin and distributions of PAH mutations in West Azerbaijan province of Iran.

Phenylketonuria (PKU) is a type of hyperphenylalaninemias, which are an inborn group of errors of the amino acid phenylalanine metabolism that are usually characterized by producing a severe mental retardation and even death if it is not treated properly. According to the World Health Organization (WHO), it is classified as rare disease. On the other hand, Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent disorders in schoolchildren. It consists of a persistent deficit pattern that includes lack of attention and / or hyperactivity and impulsivity, and it is present with an inconsistent and non adaptative frequency and severity with regard to the child's development stage (APA, 2000). Objective: To check that PKU children get significantly higher results than the control group of children for ADHD indicators. Methodology: the research includes a descriptive and quantitative approach. Interview tools were used as well as Conners Questionnaire (parents and teachers) in a sample of eight phenylketonuric children from Extremadura, who represents the total population of PKU children aged 8–13, taking into account the exclusion criteria, and eight children from Extremadura aged similarly as control group.

Antecedentes: la fenilcetonuria clásica es una encefalopatía genética caracterizada por una inhabilidad de los individuos para metabolizar la fenilalanina, por lo que su concentración plasmática se eleva a niveles tóxicos. Clínicamente se manifiesta como irritabilidad, alteración del sueño, indiferencia al medio, crisis convulsivas, retraso del neurodesarrollo, conducta autista, agresividad y discapacidad intelectual. Objetivo: describir los hallazgos y cuantificar el coeficiente de difusión aparente en los estudios de imagen de resonancia magnética de cráneo, de pacientes con fenilcetonuria clásica diagnosticada tardíamente en el Instituto Nacional de Pediatría (México). Materiales y métodos: análisis retrospectivo de imágenes cerebrales obtenidas por resonancia magnética en pacientes con fenilcetonuria clásica. Se utilizó un magneto Signa Excite de 1.5 teslas con antena cerebral de ocho canales de arreglo en fase. Se midió el coeficiente de difusión aparente en la estación de trabajo Advantage Workstation 4.2p. Resultados: en los pacientes se observaron alteraciones en las sustancias blanca, gris, o ambas. En la sustancia blanca las lesiones hiperintensas en el área peritrigonal fueron las más frecuentes; se encontraron alteraciones bilaterales en la sustancia blanca frontal, temporal, occipital, subcortical y periventricular. Se observó disminución del coeficiente de difusión aparente en la sustancia blanca peritrigonal, occipital, cuerpo calloso, ganglios basales y cerebelo. Un paciente tenía dos quistes aracnoideos. Conclusión: todos los pacientes estudiados tuvieron las anormalidades características de la enfermedad en las imágenes de resonancia magnética. Los mecanismos causantes de las lesiones cerebrales en la fenilcetonuria, su distribución espacial y su evolución son poco conocidos y requieren de investigaciones posteriores.

Objective: To characterize adherence to Phenylketonuria (PKU) management practices among PKU patients treated at reference sites around Argentina, Brazil, and Mexico., Methods: This is a retrospective, observational, multicenter, and multinational survey-based study using aggregate data. From an initial list of 40 sites, 22 clinicians expressed interest in completing the survey, with 20 clinicians from 20 unique sites fulfilling all the study criteria. The Survey contained 28 questions, including respondent's clinic characteristics, clinic PKU treatment recommendations, and patient adherence to clinic recommendations. Survey was available in local languages, and the respondents were asked to consult their clinic records to complete their responses. Adherence was assessed by target blood phenylalanine (Phe), target blood testing frequency, and clinic visits., Results: A total of 1077 (out of 1377) actively managed PKU patients (seen in the clinic in the last 3 years) from 13 clinics in Brazil, six in Argentina, and one in Mexico were analyzed. Upper blood Phe target was set over 360 μMol/L in 70% of the clinics for adult patients. Around 40% of the patients >30 years old had Phe blood tests done twice a year or less, with 60% of the clinics recommending semestral visits for adults <30 years old. Twice a month was the most common frequency of visits for <1 year old. The COVID-19 pandemic was a disruptor for frequency of visits and exams., Conclusions: These results show that there is still room for improvement in terms of adherence, namely in adults and older children. More efforts must be made to educate patients and healthcare professionals about the importance of treatment adherence, accompanied by public policies that expand access to pharmacological and dietary treatment with diversity and quality to improve adherence to adequate blood Phe levels., Competing Interests: AC: The author reports no Conflict of Interests. NS: The author has been engaged as a speaker and received fees and travel support from Biomarin. MP: The author reports no Conflict of Interests. MVA: The author received speaker fees and travel support from pharmaceutical companies. EJ: The author declares that she was a former employee of BioMarin and is a BioMarin stock owner. DRFV: Currently an employee of BioMarin. DM: The author declares that she was a former BioMarin employee and a Biomarin stock owner from 2016 to 2021. GCC: The author reports no Conflict of Interests. HE: The author reports no Conflict of Interests. KHN: The author received Travel support from Perkin Elmer. MLA: The author reports no Conflict of Interests. RBC: The author reports no Conflict of Interests. TA: Received honoraria related to data collection. IVDS: The author reports no Conflict of Interests., (© 2023 The Authors.)

Measurement of plasma and dried blood spot (DBS) phenylalanine (Phe) is key to monitoring patients with phenylketonuria (PKU). The relationship between plasma and capillary DBS Phe concentrations has been investigated previously, however, differences in methodology, calibration approach and assumptions about the volume of blood in a DBS sub-punch has complicated this. Volumetric blood collection devices (VBCDs) provide an opportunity to re-evaluate this relationship. Paired venous and capillary samples were collected from patients with PKU ( n  = 51). Capillary blood was collected onto both conventional newborn screening (NBS) cards and VBCDs. Specimens were analysed by liquid-chromatography tandem mass-spectrometry (LC-MS/MS) using a common calibrator. Use of VBCDs was evaluated qualitatively by patients. Mean bias between plasma and volumetrically collected capillary DBS Phe was -13%. Mean recovery (SD) of Phe from DBS was 89.4% (4.6). VBCDs confirmed that the volume of blood typically assumed to be present in a 3.2 mm sub-punch is over-estimated by 9.7%. Determination of the relationship between plasma and capillary DBS Phe, using a single analytical method, common calibration and VBCDs, demonstrated that once the under-recovery of Phe from DBS has been taken into account, there is no significant difference in the concentration of Phe in plasma and capillary blood. Conversely, comparison of plasma Phe with capillary DBS Phe collected on a NBS card highlighted the limitations of this approach. Introducing VBCDs for the routine monitoring of patients with PKU would provide a simple, acceptable specimen collection technique that ensures consistent sample quality and produces accurate and precise blood Phe results which are interchangeable with plasma Phe., Competing Interests: Rachel Carling, Zoe Barclay, Nathan Cantley, Erin Emmett, Sarah Hogg, Yael Finezilber, Danja Schulenburg‐Brand, Laine Murphy and Stuart Moat declare that they have no conflict of interest., (© 2023 The Authors. JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

Purpose: Elevated serum phenylalanine (Phe) levels due to biallelic pathogenic variants in phenylalanine hydroxylase (PAH) may cause neurodevelopmental disorders or birth defects from maternal phenylketonuria. New Phe reduction treatments have been approved in the last decade, but uncertainty on the optimal lifespan goal Phe levels for patients with PAH deficiency remains., Methods: We searched Medline and Embase for evidence of treatment concerning PAH deficiency up to September 28, 2021. Risk of bias was evaluated based on study design. Random-effects meta-analyses were performed to compare IQ, gestational outcomes, and offspring outcomes based on Phe ≤ 360 μmol/L vs > 360 μmol/L and reported as odds ratio and 95% CI. Remaining results were narratively synthesized., Results: A total of 350 studies were included. Risk of bias was moderate. Lower Phe was consistently associated with better outcomes. Achieving Phe ≤ 360 μmol/L before conception substantially lowered the risk of negative effect to offspring in pregnant individuals (odds ratio = 0.07, 95% CI = 0.04-0.14; P < .0001). Adverse events due to pharmacologic treatment were common, but medication reduced Phe levels, enabling dietary liberalization., Conclusions: Reduction of Phe levels to ≤360 μmol/L through diet or medication represents effective interventions to treat PAH deficiency., Competing Interests: Conflict of Interest J.A.H. is associated with a clinical laboratory that performs biochemical genetic, genetic, and genomic analyses on a fee-for-service basis. All other authors declare no conflicts of interest., (Copyright © 2022 American College of Medical Genetics and Genomics. Published by Elsevier Inc. All rights reserved.)

Abstract Background Phenylketonuria (PKU) is caused by a deficiency in phenylalanine hydroxylase enzyme activity that leads to phenylalanine (Phe) accumulation in the blood and brain. Elevated blood Phe levels are associated with complications in adults, including neurological, psychiatric, and cognitive issues. Even with nutrition and pharmacological management, the majority of adults with PKU do not maintain blood Phe levels at or below guideline recommended levels. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is an investigational enzyme substitution therapy to lower blood Phe in adults with PKU. Methods Pegvaliase was administered using an induction, titration, and maintenance dosing regimen in adults with PKU naïve to pegvaliase treatment. Doses were gradually increased until blood Phe ≤ 600 μmol/L was achieved. The maintenance dose was the dose at which participants achieved and sustained blood Phe ≤ 600 μmol/L for at least 4 weeks without dose modification. Analyses were performed for participants who achieved (Group A, n = 11) and did not achieve (Group B, n = 13) maintenance dose during the first 24 weeks of study treatment. Results Baseline mean blood Phe for Group A and Group B were 1135 μmol/L and 1198 μmol/L, respectively. Mean blood Phe ≤ 600 μmol/L was achieved for Group A by Week 11 (mean blood Phe of 508 ± 483 μmol/L) and for Group B by Week 48 (mean blood Phe of 557 ± 389 μmol/L). The most common adverse events involved hypersensitivity reactions, which were mostly mild to moderate in severity and decreased over time. One participant in Group B had four acute systemic hypersensitivity events of anaphylaxis consistent with clinical National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network criteria; all events were non-IgE mediated and resolved without sequelae, with pegvaliase dosing discontinued after the fourth event. The incidence and titers of anti-drug antibodies were generally lower in Group A compared to Group B. Conclusions Pegvaliase administered with an induction, titration, and maintenance dosing regimen demonstrated substantial efficacy at reducing blood Phe in both Group A and Group B by Week 48, with a manageable safety profile in most participants. Blood Phe reduction due to pegvaliase appears to be related to dose, treatment duration, and individual immune response; given additional time on treatment and dose titration, later Phe responders (Group B) achieved benefit similar to early Phe responders (Group A), with similar long-term safety profiles. [ABSTRACT FROM AUTHOR]

Abstract Phenylketonuria (PKU) is a genetic inborn error in metabolism that impacts many people globally, with profound individual and societal consequences when left untreated. The journey of phenylalanine ammonia lyase (PAL) from plant enzyme to enzyme substitution therapy for PKU is a fascinating story that illustrates the importance of collaboration between basic scientists and industry in the drug development process. The story begins with the curiosity of plant physiologists about the origin of lignin, a polymer involved in maintaining the rigidity of plants. They learned that the critical element in this synthesis was an intermediary enzyme that deaminates phenylalanine to cinnamic acid and ammonia (later called phenylalanine ammonia lyase or PAL). Recognition of this ability to metabolize phenylalanine led to subsequent consideration of PAL as a treatment for PKU. This was initially attempted as enteral therapy with extracted enzyme, but that showed only minimal efficacy. Crucially, further development of PAL as a therapy for PKU required quantities of enzyme that could only be obtained after successfully cloning the gene, expressing the enzyme in vitro and modifying the protein via PEGylation to enable parenteral administration of this non-mammalian enzyme. Ultimately, PEGylated PAL was developed as an enzyme substitution therapy for PKU now approved under the name “Palynziq.” The multidisciplinary academic-industrial partnership engaged throughout this process has been key to the successful pursuit of this therapeutic possibility and serves as a model for the development of future innovative therapies. [ABSTRACT FROM AUTHOR]

Introduction Pegvaliase is a recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) enzyme under investigation for treatment of adult phenylketonuria (PKU). This manuscript describes results of a randomized discontinuation trial (RDT) designed to evaluate the effects of pegvaliase treatment on blood phenylalanine (Phe) and neuropsychiatric outcomes in adults with PKU. Methods PRISM-2 is a 4-part, Phase 3 study that enrolled adults with PKU receiving pegvaliase treatment (initiated in a prior Phase 2 or Phase 3 study). The RDT, Part 2 of PRISM-2, was an 8-week trial that evaluated change in blood Phe concentrations, neuropsychiatric and neurocognitive measures, and safety outcomes in PRISM-2 participants who had achieved at least a 20% blood Phe reduction from pre-treatment baseline with pegvaliase treatment. Participants were randomized 2:1 to either continue pegvaliase (20 mg/day or 40 mg/day) or switch to matching placebo. Results The pooled pegvaliase group enrolled 66 participants and each placebo group enrolled 14 participants. The primary endpoint of change in blood Phe concentration from RDT entry to RDT Week 8 was met with clinically meaningful and statistically significant differences between the pegvaliase and placebo groups. Mean (SD) blood Phe at the beginning of the RDT when all participants were receiving pegvaliase was 563.9 μM (504.6) in the group assigned to the 20 mg/day placebo group ( n  = 14), 508.2 μM (363.7) in those assigned to the 40 mg/day placebo group (n = 14), and 503.9 μM (520.3) in those assigned to continue pegvaliase treatment ( n  = 58). At Week 8 of the RDT, the least squares mean change (95% confidence interval) in blood Phe was 949.8 μM (760.4 to 1139.1) for the 20 mg/day placebo group and 664.8 μM (465.5 to 864.1) for the 40 mg/day placebo group in comparison to 26.5 μM (−68.3 to 121.3) for the pooled (20 mg/day and 40 mg/day) pegvaliase group ( P  < 0.0001 for pooled pegvaliase group vs each placebo group). Adverse events (AEs) were usually lower in the pooled placebo group when compared to the pooled pegvaliase group. The most common AEs for the pooled pegvaliase and pooled placebo groups were arthralgia (13.6% and 10.3%, respectively), headache (12.1% and 24.1%), anxiety (10.6% and 6.9%), fatigue (10.6% and 10.3%), and upper respiratory tract infection (1.5% and 17.2%). Conclusion Mean blood Phe reduction was sustained in the pegvaliase group, while placebo groups had mean blood Phe concentration increase toward pre-treatment baseline levels. Results from this study confirmed the efficacy of pegvaliase in maintaining reduced blood Phe concentrations with a manageable safety profile for most participants. [ABSTRACT FROM AUTHOR]

Background: Inherited metabolic diseases (IMD) are a large group of rare single-gene disorders that are typically diagnosed early in life. There are important evidence gaps related to the comparative effectiveness of therapies for IMD, which are in part due to challenges in conducting randomized controlled trials (RCTs) for rare diseases. Registry-based RCTs present a unique opportunity to address these challenges provided the registries implement standardized collection of outcomes that are important to patients and their caregivers and to clinical providers and healthcare systems. Currently there is no core outcome set (COS) for studies evaluating interventions for paediatric IMD. This protocol outlines a study that will establish COS for each of two relatively common IMD in children, phenylketonuria (PKU) and medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.Methods: This two-part study is registered with the Core Outcome Measures in Effectiveness Trials (COMET) initiative. Part 1 includes a rapid review and development of an evidence map to identify a comprehensive listing of outcomes reported in past studies of PKU and MCAD deficiency. The review follows established methods for knowledge synthesis, including a comprehensive search strategy, two stages of screening citations against inclusion/exclusion criteria by two reviewers working independently, and extraction of important data elements from eligible studies, including details of the outcomes collected and outcome measurement instruments. The review findings will inform part 2 of our study, a set of Delphi surveys to establish consensus on the highest priority outcomes for each condition. Healthcare providers, families of children with PKU or MCAD deficiency, and health system decision-makers will be invited to participate in two to three rounds of Delphi surveys. The design of the surveys will involve parents of children with IMD who are part of a family advisory forum.Discussion: This protocol is a crucial step in developing the capacity to launch RCTs with meaningful outcomes that address comparative effectiveness questions in the field of paediatric IMD. Such trials will contribute high-quality evidence to inform decision-making by patients and their family members, clinicians, and policy-makers. [ABSTRACT FROM AUTHOR]

PKU patients react to therapy with a low phenylalanine diet, but adherence to this diet is troublesome, subsequently the expansion of alternative ways is demand. Phenylalanine ammonia lyase (PAL) is one of this ways, which converts phenylalanine to harmless metabolites; trans-cinnamic acid and ammonia. In the current study, the extraction of PAL enzyme was used to investigate the efficiency for production of functional PKU egg white and mushroom flour with good quality by evaluation of colour characteristics, determination of phenylalanine concentrations and genetic materials expression of PKU related genes and DNA damage. Results indicated that the PAL enzyme treated of egg white and mushroom flour was stable colour and the calculated reduction per cent in phenylalanine concentration from female mice fed on untreated and PAL–treated samples was 22.77% in egg white and 31.37% in mushroom flour. Also, the results revealed that female mice fed on diet contained treated egg white exhibited low expression levels of PKU exons (3, 6, 7, 11, and 12) and low DNA damage which were similar to those in control mice. [ABSTRACT FROM AUTHOR]

In order to diagnose the nutritional status and to provide a personalized treatment in PKU patients, an evaluation of nutritional status should be conducted. Several components are involved in the nutritional assessment; among the parameters there are anthropometric evaluation: weight, height, head circumference; biochemical: proteins, amino acids, vitamins, inorganic nutrients, essential fatty acids; clinical: deficiencies in hair, skin, oral cavity , eyes, etc.; dietary assessment: quantification of energy intake, macronutrients and micronutrients through several tools such as the 24-hour recall; finally it must be taken into account the interaction of nutrients such as carnitine, fatty acids, vitamin B complex, among others, with drugs, which are often anticonvulsants, in order to plan the diet and prevent a future nutritional deficiency. It is important to perform the nutritional status assessment frequently in patients with PKU because the dietary management is essential to prevent neurological problems.

Objective: To gauge the gross and fine motor development of early treated phenylketonuria (ETPKU) in children in the age range of 1–4 years. Materials & Methods: A cross-sectional analytic study was conducted in PKU clinics (reference clinics for PKU follow-up), Tehran, Iran. Seventy children with ETPKU were selected as the case group for the study. ETPKU children were those with early and continuous treatment with a phenylalaninerestricted diet (the mean of blood phenylalanine level during the recent 6 months was 2–6 mg/dL or 120–360 mmol/L). Also, 100 healthy and normal children matched with the ETPKU group for age were randomly selected from 4 kindergartens in four parts of Tehran as a control group. The measurements consisted of a demographic questionnaire, Peabody Developmental Motor Scale-2 (PDMS-2), and pediatrician assessment. Motor quotients were determined by PDMS-2 and then compared in both groups by two independent samples t-test. Results: The mean ages in case and control group were 28.5 (±11.6) and 29.7 (±11.3) months, respectively. Comparison of the mean fine, gross, and total developmental motor quotients (DMQs) showed statistically significant differences between the two groups (P

Objective: To explore the pregnancy-related stresses anticipated and experienced by women with phenylketonuria (PKU) and the coping strategies and supports utilised or anticipated to be beneficial during pregnancy. Methods: Thematic analysis of interview data from eight women with PKU in a cross-sectional, qualitative study. Five of the participants had never had a pregnancy but were planning to in the future, two participants had children, and one participant was pregnant. Results: The central concern regarding pregnancy was achieving and maintaining the essential low Phe levels, in the context of the devastating effects of high levels. The Transactional Model of Stress and Coping was utilised to understand the coping strategies and supports utilised or anticipated to be beneficial during pregnancy. Similarities and differences between the women who had experienced pregnancy, and those who were planning a pregnancy in the future were evident in key coping strategies, with knowledge seeking, positive reappraisal, and reassurance seeking reported. Support from health professionals and other mothers with PKU was key for all women. Psychological support was identified as a resource perceived to be beneficial to promote psychological well-being during pregnancy but not yet provided. Conclusion: Pregnancy is associated with significant stresses for women with PKU. Clinical implications of the findings include provision of psychological support.

The nutritional and metabolic characteristics of adult phenylketonuria (PKU) patients in the UK with varying dietary adherence is unknown. In other countries, nutritional and metabolic abnormalities have been reported in nonadherent patients compared to adherent counterparts. A pooled analysis of primary baseline data from two UK multi-centre studies was therefore performed to establish whether this is true from a UK perspective. Adult PKU patients who had provided 3-day food records and amino acid blood samples were included and grouped according to dietary adherence (adherent; n = 16 vs. nonadherent; n = 14). Nonadherent patients consumed greater amounts of natural protein compared to adherent patients (61.6 ± 30.7 vs. 18.3 ± 7.7 g/day; q < 0.001). In contrast, the contribution of protein substitutes to total protein intake was lower in nonadherent compared to adherent patients (3.9 ± 9.2 g/day vs. 58.6 ± 10.2 g/day; q < 0.001). Intakes of iron, zinc, vitamin D3, magnesium, calcium, selenium, iodine, vitamin C, vitamin A and copper were significantly lower in nonadherent compared to adherent patients and were below UK Reference Nutrient Intakes. Similarly, intakes of thiamin, riboflavin, niacin, vitamin B6 and phosphorus were significantly lower in nonadherent compared to adherent patients but met the UK Reference Nutrient Intakes. Phenylalanine concentrations in nonadherent patients were significantly higher than adherent patients (861 ± 348 vs. 464 ± 196 µmol/L; q = 0.040) and fell outside of European treatment target ranges. This study shows the nutritional and metabolic consequences of deviation from phenylalanine restriction and intake of PKU protein substitutes in nonadherent adult PKU patients. Collectively, these data further underlie the importance of life-long adherence to the PKU diet.

Noncompliance is widespread in adults with PKU and is associated with adverse metabolic, nutritional and cognitive abnormalities. Returning to the PKU diet is important for this at-risk population, yet for many this is challenging to achieve. Strategies that ease the return to the PKU diet, while offering nutritional and cognitive advantages, are needed. Twelve PKU adults (33.7 ± 2.6 years), who had been noncompliant for 4.5 years (range: 1 to 11 years), took 33 g of a low-volume, nutrient-enriched, protein substitute daily for 28 days. Outcomes of eating behaviour, nutrient intake and mood were assessed at entry (baseline, days 1−3) and after the intervention period (days 29−31). At baseline, intakes of natural protein and estimated phenylalanine were high (66.4 g and 3318.5 mg, respectively) and intakes of calcium, magnesium, iron, zinc, iodine and vitamin D were below country-specific recommendations. With use of the experimental protein substitute, natural protein and estimated phenylalanine intake declined (p = 0.043 for both). Fat and saturated fat intakes also decreased (p = 0.019 and p = 0.041, respectively), while energy and carbohydrate intake remained unchanged. Micronutrient intake increased (p ≤ 0.05 for all aforementioned) to levels well within reference nutrient intake recommendations. Blood vitamin B12 and vitamin D increased by 19.8% and 10.4%, respectively. Reductions in anxiety and confusion were also observed during the course of the study yet should be handled as preliminary data. This study demonstrates that reintroducing a low-volume, nutrient-enriched protein substitute delivers favourable nutritional and possible mood benefits in noncompliant PKU patients, yet longer-term studies are needed to further confirm this. This preliminary knowledge should be used in the design of new strategies to better facilitate patients’ return to the PKU diet, with the approach described here as a foundation.

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism caused by deficiency in the enzyme phenylalanine hydroxylase that converts phenylalanine into tyrosine. If left untreated, PKU results in increased phenylalanine concentrations in blood and brain, which cause severe intellectual disability, epilepsy and behavioural problems. PKU management differs widely across Europe and therefore these guidelines have been developed aiming to optimize and standardize PKU care. Professionals from 10 different European countries developed the guidelines according to the AGREE (Appraisal of Guidelines for Research and Evaluation) method. Literature search, critical appraisal and evidence grading were conducted according to the SIGN (Scottish Intercollegiate Guidelines Network) method. The Delphi-method was used when there was no or little evidence available. External consultants reviewed the guidelines. Using these methods 70 statements were formulated based on the highest quality evidence available. The level of evidence of most recommendations is C or D. Although study designs and patient numbers are sub-optimal, many statements are convincing, important and relevant. In addition, knowledge gaps are identified which require further research in order to direct better care for the future. [ABSTRACT FROM AUTHOR]

In 2019, pegvaliase was approved in Europe for the treatment of phenylketonuria (PKU) in patients aged 16 years and older with blood phenylalanine (Phe) concentrations above 600 μmol/L despite prior management with available treatment options. Since its European approval, German metabolic centres have gained valuable experience, which may be of benefit to other treatment centres managing patients on pegvaliase. After a virtual meeting that was attended by nine German physicians, three German dietitians and one American physician, a follow-up discussion was held via an online platform to develop a set of recommendations on the use of pegvaliase in Germany. Eight German physicians contributed to the follow-up discussion and subsequent consensus voting, using a modified Delphi technique. The recommendations were supported by literature and retrospectively collected patient data. Consensus (≥75% agreement) was achieved on 25 recommendations, covering seven topics deemed relevant by the expert panel when considering pegvaliase an option for the treatment of patients with PKU. In addition to the recommendations, a retrospective chart review was conducted in seven of the centres and included 71 patients who initiated treatment with pegvaliase. Twenty-seven patients had been treated for at least 24 months and 23 (85.2%) had achieved blood Phe ≤600 μmol/L with some degree of diet normalisation. Of these patients, 14 had physiological blood Phe on a normalised diet. The practical consensus recommendations provide guidance on the different steps along the pegvaliase journey from clinical site requirements to treatment goals and outcomes. The recommendations are intended to support less experienced European metabolic centres with the implementation of pegvaliase, emphasising that a core treatment team consisting of at least a dietitian and metabolic physician is sufficient to initiate pegvaliase and support patients during their treatment journey. [ABSTRACT FROM AUTHOR]

Background: Dietary intervention is to date the mainstay treatment to prevent toxic phenylalanine (Phe) accumulation in PKU patients. Despite success preventing central nervous system damage, there is increasing evidence of possible other unfavorable outcomes affecting other systems, e.g. kidney and bone; underlying mechanisms are yet to be fully elucidated., Methods: This observational, cross-sectional and descriptive study investigated 20 adult with PKU evaluating biochemical parameters, BMD measurements and extrapolating data from 3-days food records and protein substitutes (PS) and special low protein foods (SLPF) composition., Results: Blood gas venous analysis (VBG) indices were indicative of metabolic acidosis in 60% of PKU patients and VBG pH significantly correlated with BMD's Z -score ( p -value = 0.022) even if its overall mean was in range (-1.29). Low bone mineral density for chronological age ( Z -score < - 2.0) was found in 4 patients (20%). Indices of kidney function were not impaired. All used PS had a moderate excess of acidity, while SLPF were alkalizing and type/variety of consumed vegetables did not determine significant changes in acid-base equilibrium. Total intakes of potassium and magnesium were lower than expected., Discussion: PKU patients seem to be at risk of metabolic acidosis, directly linked to possible low bone mineralization. This may be related to the acidic composition of PS, potentially capable of acidifying the entire diet. Reported low intakes of potassium and magnesium may be relevant to these observations. Further studies are needed to better address these topics., Competing Interests: None., (© 2023 The Authors.)

Introduction: Clinical management of rare diseases often fails to acknowledge the challenges faced by caregivers. Whilst management of phenylketonuria (PKU) may not be considered as dire as other conditions, most studies primarily concentrate on clinical issues, dietary adherence, or the quality of life of the PKU patients, leaving caregivers in the background. The aim of the study was to evaluate the psychosocial effects of PKU on family caregivers., Methods: Between October 30th, 2022 and February 28th, 2023, we collected data from caregivers of children with PKU using an anonymous, self-administered, computer-assisted online questionnaire. The survey was distributed among to patients during their regular visits to five Polish PKU treatment centers., Results: A total of 159 Polish caregivers of children with PKU completed the survey. This research shows that while women caregivers were more likely to be unemployed due to their responsibilities for childcare (50.3% compared to 0% for men), and men caregivers were more likely to be employed full-time (93.8% compared to 40.6% for women), the former reported higher emotional engagement in caregiving (88.1% vs 56.3% respectively). Significantly, unemployed mothers reported higher levels of loneliness, helplessness, and emotional control problems, and lacked psychological/emotional support more often than employed mothers. This research also shows a statistically significant positive correlation between mothers' education level and financial situation ( p  < 0.05) and education level and professional activity ( p  < 0.01). Additionally, a significant positive correlation was found between perceived financial situation and feeling of happiness ( p  < 0.001), and between financial situation and professional activity (p < 0.001). Finally, a significant positive correlation was observed between feeling of happiness and professional activity ( p  < 0.05)., Conclusions: According to our findings, there is a link between subjective happiness, financial situation, and professional activity among female caregivers. The relationship between these factors goes beyond just the income earned from work. The results of our study imply that there could even be a therapeutic advantage for working mothers. It is crucial to recognize the emotional difficulties that employed mothers may experience while taking care of a child with PKU, and to provide them with the necessary assistance and resources to meet their needs. Additionally, our results may provide a foundation for redefining the support system for caregivers in Poland., Competing Interests: The authors declare that they have no conflict of interest., (© 2023 The Authors. Published by Elsevier Inc.)

To build therapeutic strains, Escherichia coli Nissle (EcN) have been engineered to express antibiotics, toxin-degrading enzymes, immunoregulators, and anti-cancer chemotherapies. For efficacy, the recombinant genes need to be highly expressed, but this imposes a burden on the cell, and plasmids are difficult to maintain in the body. To address these problems, we have developed landing pads in the EcN genome and genetic circuits to control therapeutic gene expression. These tools were applied to EcN SYNB1618, undergoing clinical trials as a phenylketonuria treatment. The pathway for converting phenylalanine to trans-cinnamic acid was moved to a landing pad under the control of a circuit that keeps the pathway off during storage. The resulting strain (EcN SYN8784) achieved higher activity than EcN SYNB1618, reaching levels near when the pathway is carried on a plasmid. This work demonstrates a simple system for engineering EcN that aids quantitative strain design for therapeutics., Competing Interests: Declaration of interests Synlogic is a public, for-profit company whose business is the development of bacterial therapeutics to treat human disease, including the PKU treatment described in this manuscript. Some authors hold stock in Synlogic and may gain or lose financially through publication. C.A.V. previously served on their Scientific Advisory Board (SAB)., (Copyright © 2023 Elsevier Inc. All rights reserved.)