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Turgeon C, Casas K, Flanagan R, White A, Peck D, Pino GB, Jones AS, Gavrilov D, Oglesbee D, Schultz MJ, Tortorelli S, Matern D, Hall PL. Pre-analytic decrease of phenylalanine in plasma of patients with phenylketonuria treated with pegvaliase. Mol Genet Metab Rep 2024; 40:101110. [PMID: 39022300 PMCID: PMC11252920 DOI: 10.1016/j.ymgmr.2024.101110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 06/18/2024] [Accepted: 06/18/2024] [Indexed: 07/20/2024] Open
Abstract
Treatment of phenylketonuria (PKU) has evolved since the initial introduction of a phenylalanine (Phe) restricted diet. The most recent option for adults affected with PKU is treatment with an alternate enzyme, phenylalanine ammonia lyase (PAL), that metabolizes excess Phe. Proper management of all patients with PKU relies on accurate measurement of Phe levels in blood, to comply with guidance intended to minimize the neurological symptoms. Recently, our laboratory was notified of discrepant results for a patient with PKU who is treated with pegvaliase. Two specimens were collected at the same time but yielded unexpectedly different Phe concentrations. After exclusion of specimen mix-ups or analytical errors, we suspected that there was residual pegvaliase activity in the specimens continuing to degrade Phe after collection. To investigate this possibility, we performed spiking studies that showed the degradation of Phe over time at ambient temperatures. Sample preparation by protein crash appears to deactivate pegvaliase and prevents further Phe degradation. However, because pegvaliase deactivation would be required immediately following blood collection, appropriate mitigation measures must be implemented, including stringent pre-analytical requirements, alternate sample matrices such as dried blood spots, or point of care testing. Until then, health care professionals need to be cautious in their interpretation of Phe levels in their patients with PKU that are treated with pegvaliase.
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Affiliation(s)
- Coleman Turgeon
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | | | - Ryan Flanagan
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Amy White
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Dawn Peck
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Gisele Bentz Pino
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | | | - Dimitar Gavrilov
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Devin Oglesbee
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Matthew J. Schultz
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Silvia Tortorelli
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Dietrich Matern
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Patricia L. Hall
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
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Lopez A, Havranek B, Papadantonakis GA, Islam SM. In silico screening and molecular dynamics simulation of deleterious PAH mutations responsible for phenylketonuria genetic disorder. Proteins 2021; 89:683-696. [PMID: 33491267 DOI: 10.1002/prot.26051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 01/08/2021] [Accepted: 01/21/2021] [Indexed: 12/23/2022]
Abstract
Phenylketonuria (PKU) is a genetic disorder that if left untreated can lead to behavioral problems, epilepsy, and even mental retardation. PKU results from mutations within the phenylalanine-4-hydroxylase (PAH) gene that encodes for the PAH protein. The study of all PAH causing mutations is improbable using experimental techniques. In this study, a collection of in silico resources, sorting intolerant from tolerant, Polyphen-2, PhD-SNP, and MutPred were used to identify possible pathogenetic and deleterious PAH non-synonymous single nucleotide polymorphisms (nsSNPs). We identified two variants of PAH, I65N and L311P, to be the most deleterious and disease causing nsSNPs. Molecular dynamics (MD) simulations were carried out to characterize these point mutations on the atomic level. MD simulations revealed increased flexibility and a decrease in the hydrogen bond network for both mutants compared to the native protein. Free energy calculations using the MM/GBSA approach found that BH4 , a drug-based therapy for PKU patients, had a higher binding affinity for I65N and L311P mutants compared to the wildtype protein. We also identify important residues in the BH4 binding pocket that may be of interest for the rational drug design of other PAH drug-based therapies. Lastly, free energy calculations also determined that the I65N mutation may impair the dimerization of the N-terminal regulatory domain of PAH.
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Affiliation(s)
- Andrea Lopez
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Brandon Havranek
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, USA
| | | | - Shahidul M Islam
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, USA
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Wang X, Wang Y, Ma D, Zhang Z, Li Y, Yang P, Sun Y, Jiang T. Neonatal screening and genotype-phenotype correlation of hyperphenylalaninemia in the Chinese population. Orphanet J Rare Dis 2021; 16:214. [PMID: 33980295 PMCID: PMC8114530 DOI: 10.1186/s13023-021-01846-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/04/2021] [Indexed: 11/10/2022] Open
Abstract
Background Hyperphenylalaninemia (HPA) is the most common amino acid metabolic disease involving phenylalanine hydroxylase (PAH, OMIM*612,349) deficiency or coenzyme tetrahydrobiopterin (BH4) deficiency. Patients with severe HPA often have a difficult life. Early diagnosis of HPA before the development of symptoms is possible via neonatal screening, facilitating appropriate treatment and reducing mortality and disability rates. This study revealed the prevalence, mutational and phenotypic spectrum, and prognosis of HPA by neonatal screening from January 2001 to September 2020 in Nanjing, Jiangsu Province, China. Methods Through a retrospective analysis of the information available in the neonatal screening database, the clinical presentations, laboratory data, molecular characteristics and treatment follow-up data of HPA patients detected by neonatal screening were evaluated. Results We diagnosed 181 patients with HPA from 1 to 957 newborns, giving an incidence of 1:6873. Among these patients, 177 were identified as PAH deficient and four patients were BH4 deficient. The average current age of the patients was 6.38 years old. The most common mutations of PAH were c.728 C > A/ p.Arg243Gln (13.83 %), c.158G > A/ p.Arg53His (9.57 %), c.611 A > G/ p.Tyr204Cys (7.44 %), and c.721 C > T/ p.Arg241Cys (6.38 %). Conclusions This study revealed the prevalence, phenotype-genotype, and prognosis of HPA in China and contributes to the updating of PAHD data for China and worldwide. Our study not only expanded the spectrum of phenotypes and genotype but also provided a valuable tool for improved genetic counseling and management of future cases. Supplementary Information The online version contains supplementary material available at 10.1186/s13023-021-01846-w.
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Affiliation(s)
- Xin Wang
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Yanyun Wang
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Dingyuan Ma
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Zhilei Zhang
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Yahong Li
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Peiying Yang
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Yun Sun
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China
| | - Tao Jiang
- Genetic Medicine Center, Nanjing Maternity and Child Health Care Hospital, Women's Hospital of Nanjing Medical University, 123 Tianfei St., Qinhuai District, Nanjing, 210004, People's Republic of China.
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Vockley J, Dobrowolski SF, Arnold GL, Guerrero RB, Derks TGJ, Weinstein DA. Complex patterns of inheritance, including synergistic heterozygosity, in inborn errors of metabolism: Implications for precision medicine driven diagnosis and treatment. Mol Genet Metab 2019; 128:1-9. [PMID: 31358473 PMCID: PMC8931500 DOI: 10.1016/j.ymgme.2019.07.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/18/2019] [Accepted: 07/18/2019] [Indexed: 01/03/2023]
Abstract
Inborn errors of metabolism have traditionally been viewed as the quintessential single gene disorders; defects in one gene leads to loss of activity of one enzyme causing a metabolic imbalance and clinical disease. However, reality has never been quite that simple, and the classic "one gene-one enzyme" paradigm has been upended in many ways. Multiple gene defects can lead to the same biochemical phenotype, often with different clinical symptoms. Additionally, different mutations in the same gene can cause variable phenotypes, often most dramatic when a disease can be identified by pre-symptomatic screening. Moreover, response to therapy is not homogeneous across diseases and specific mutations. Perhaps the biggest deviation from traditional monogenic inheritance is in the setting of synergistic heterozygosity, a multigenic inheritance pattern in which mutations in multiple genes in a metabolic pathway lead to sufficient disruption of flux through the pathway, mimicking a monogenic disorder caused by homozygous defects in one gene in that pathway. In addition, widespread adoption of whole exome and whole genome sequencing in medical genetics has led to the realization that individual patients with apparently hybrid phenotypes can have mutations in more than one gene, leading to a mixed genetic disorder. Each of these situations point to a need for as much precision as possible in diagnosing metabolic disease, and it is likely to become increasingly critical to drive therapy. This article examines examples in traditional monogenic disorders that illustrates these points and define inborn errors of metabolism as complex genetic traits on the leading edge of precision medicine.
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Affiliation(s)
- Jerry Vockley
- University of Pittsburgh School of Medicine, Department of Pediatrics, Pittsburgh, PA, United States of America; UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States of America.
| | - Steven F Dobrowolski
- University of Pittsburgh School of Medicine, Department of Pathology, Pittsburgh, PA. UPMC Children's Hospital of Pittsburgh. 4401 Penn Avenue, Pittsburgh, PA 15224, United States of America
| | - Georgianne L Arnold
- University of Pittsburgh School of Medicine, Department of Pediatrics, Pittsburgh, PA, United States of America; UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, United States of America
| | | | - Terry G J Derks
- Section of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, PO box 30 001, 9700, RB, Groningen, the Netherlands
| | - David A Weinstein
- Department of Pediatrics, University of Connecticut School of Medicine, Farmington, CT 06030, United States of America; GSD Program, Connecticut Children's Medical Center, Hartford, CT 06106, United States of America
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Spécola N, Chiesa A. Alternative Therapies for PKU. JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2017. [DOI: 10.1177/2326409816685734] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Affiliation(s)
- Norma Spécola
- Unidad de Metabolismo, Hospital de Niños de La Plata, Buenos Aires, Argentina
| | - Ana Chiesa
- División de Endocrinología. Hospital de Niños R, FEI, Gutiérrez, Buenos Aires, Argentina
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Stockler-Ipsiroglu S, Yuskiv N, Salvarinova R, Apatean D, Ho G, Cheng B, Giezen A, Lillquist Y, Ueda K. Individualized long-term outcomes in blood phenylalanine concentrations and dietary phenylalanine tolerance in 11 patients with primary phenylalanine hydroxylase (PAH) deficiency treated with Sapropterin-dihydrochloride. Mol Genet Metab 2015; 114:409-14. [PMID: 25497838 DOI: 10.1016/j.ymgme.2014.11.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/20/2014] [Accepted: 11/20/2014] [Indexed: 10/24/2022]
Abstract
We analyzed long-term sustainability of improved blood Phenylalanine (Phe) control and changes to dietary Phe tolerance in 11 patients (1 month to 16 years), with various forms of primary PAH deficiency (classic, moderate, severe phenylketonuria [PKU], mild hyperphenylalaninemia [HPA]), who were treated with 15-20mg/kg/d Sapropterin-dihydrochloride during a period of 13-44 months. 7/11 patients had a sustainable, significant reduction of baseline blood Phe concentrations and 6 of them also had an increase in mg/kg/day Phe tolerance. In 2 patients with mild HPA, blood Phe concentrations remained in the physiologic range even after a 22 and 36% increase in mg/kg/day Phe tolerance and an achieved Phe intake at 105% and 268% of the dietary reference intake (DRI) for protein. 2 of these responders had classic PKU. 1 patient with mild HPA who started treatment at 2 months of life, had a significant and sustainable reduction in pretreatment blood Phe concentrations, but no increase in the mg/kg/day Phe tolerance. An increase in Phe tolerance could only be demonstrated when expressing the patient's daily Phe tolerance with the DRI for protein showing an increase from 58% at baseline to 78% of normal DRI at the end of the observation. Long-term follow-up of patients with an initial response to treatment with Sapropterin is essential to determine clinically meaningful outcomes. Phenylalanine tolerance should be expressed in mg/kg/day and/or % of normal DRI to differentiate medical therapy related from physiologic growth related increase in daily Phe intake.
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Affiliation(s)
- Sylvia Stockler-Ipsiroglu
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada.
| | - Nataliya Yuskiv
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Ramona Salvarinova
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Delia Apatean
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Gloria Ho
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Barbara Cheng
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Alette Giezen
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Yolanda Lillquist
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
| | - Keiko Ueda
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, Canada
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New Strategies for the Treatment of Phenylketonuria (PKU). Metabolites 2014; 4:1007-17. [PMID: 25375236 PMCID: PMC4279156 DOI: 10.3390/metabo4041007] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 10/27/2014] [Accepted: 10/30/2014] [Indexed: 12/19/2022] Open
Abstract
Phenylketonuria (PKU) was the first inherited metabolic disease in which dietary treatment was found to prevent the disease's clinical features. Treatment of phenylketonuria remains difficult due to progressive decrease in adherence to diet and the presence of neurocognitive defects despite therapy. This review aims to summarize the current literature on new treatment strategies. Additions to treatment include new, more palatable foods based on glycomacropeptide that contains very limited amount of aromatic amino acids, the administration of large neutral amino acids to prevent phenylalanine entry into the brain or tetrahydropterina cofactor capable of increasing residual activity of phenylalanine hydroxylase. Moreover, human trials have recently been performed with subcutaneous administration of phenylalanine ammonia-lyase, and further efforts are underway to develop an oral therapy containing phenylanine ammonia-lyase. Gene therapy also seems to be a promising approach in the near future.
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Vockley J, Andersson HC, Antshel KM, Braverman NE, Burton BK, Frazier DM, Mitchell J, Smith WE, Thompson BH, Berry SA. Phenylalanine hydroxylase deficiency: diagnosis and management guideline. Genet Med 2014; 16:188-200. [PMID: 24385074 DOI: 10.1038/gim.2013.157] [Citation(s) in RCA: 408] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 08/29/2013] [Indexed: 11/08/2022] Open
Abstract
Phenylalanine hydroxylase deficiency, traditionally known as phenylketonuria, results in the accumulation of phenylalanine in the blood of affected individuals and was the first inborn error of metabolism to be identified through population screening. Early identification and treatment prevent the most dramatic clinical sequelae of the disorder, but new neurodevelopmental and psychological problems have emerged in individuals treated from birth. The additional unanticipated recognition of a toxic effect of elevated maternal phenylalanine on fetal development has added to a general call in the field for treatment for life. Two major conferences sponsored by the National Institutes of Health held >10 years apart reviewed the state of knowledge in the field of phenylalanine hydroxylase deficiency, but there are no generally accepted recommendations for therapy. The purpose of this guideline is to review the strength of the medical literature relative to the treatment of phenylalanine hydroxylase deficiency and to develop recommendations for diagnosis and therapy of this disorder. Evidence review from the original National Institutes of Health consensus conference and a recent update by the Agency for Healthcare Research and Quality was used to address key questions in the diagnosis and treatment of phenylalanine hydroxylase deficiency by a working group established by the American College of Medical Genetics and Genomics. The group met by phone and in person over the course of a year to review these reports, develop recommendations, and identify key gaps in our knowledge of this disorder. Above all, treatment of phenylalanine hydroxylase deficiency must be life long, with a goal of maintaining blood phenylalanine in the range of 120-360 µmol/l. Treatment has predominantly been dietary manipulation, and use of low protein and phenylalanine medical foods is likely to remain a major component of therapy for the immediate future. Pharmacotherapy for phenylalanine hydroxylase deficiency is in early stages with one approved medication (sapropterin, a derivative of the natural cofactor of phenylalanine hydroxylase) and others under development. Eventually, treatment of phenylalanine hydroxylase deficiency will be individualized with multiple medications and alternative medical foods available to tailor therapy. The primary goal of therapy should be to lower blood phenylalanine, and any interventions, including medications, or combination of therapies that help to achieve that goal in an individual, without other negative consequences, should be considered appropriate therapy. Significant evidence gaps remain in our understanding of the optimum therapies for phenylalanine hydroxylase deficiency, nonphenylalanine effects of these therapies, and long-term sequelae of even well-treated disease in children and adults.
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Affiliation(s)
- Jerry Vockley
- 1] Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA [2] Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - Hans C Andersson
- Hayward Genetics Center, Tulane University Medical School, New Orleans, Louisiana, USA
| | - Kevin M Antshel
- Department of Psychology, Syracuse University, Syracuse, New York, USA
| | - Nancy E Braverman
- Department of Human Genetics and Pediatrics, McGill University, Montreal, Quebec, Canada
| | - Barbara K Burton
- Department of Pediatrics, Northwestern University Medical School, Chicago, Illinois, USA
| | - Dianne M Frazier
- Department of Pediatrics, University of North Carolina, at Chapel Hill, Chapel Hill, North Carolina, USA
| | - John Mitchell
- Department of Human Genetics and Pediatrics, McGill University, Montreal, Quebec, Canada
| | - Wendy E Smith
- Department of Pediatrics, Maine Medical Center, Portland, Maine, USA1
| | - Barry H Thompson
- The American College of Medical Genetics and Genomics, Bethesda, Maryland, USA
| | - Susan A Berry
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA
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Keil S, Anjema K, van Spronsen FJ, Lambruschini N, Burlina A, Bélanger-Quintana A, Couce ML, Feillet F, Cerone R, Lotz-Havla AS, Muntau AC, Bosch AM, Meli CAP, Billette de Villemeur T, Kern I, Riva E, Giovannini M, Damaj L, Leuzzi V, Blau N. Long-term follow-up and outcome of phenylketonuria patients on sapropterin: a retrospective study. Pediatrics 2013; 131:e1881-8. [PMID: 23690520 DOI: 10.1542/peds.2012-3291] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Sapropterin dihydrochloride, the synthetic form of 6R-tetrahydrobiopterin (BH4), is an approved drug for the treatment of patients with BH4-responsive phenylketonuria (PKU). The purpose of this study was to assess genotypes and data on the long-term effects of BH4/sapropterin on metabolic control and patient-related outcomes in 6 large European countries. METHODS A questionnaire was developed to assess phenotype, genotype, blood phenylalanine (Phe) levels, Phe tolerance, quality of life, mood changes, and adherence to diet in PKU patients from 16 medical centers. RESULTS One hundred forty-seven patients, of whom 41.9% had mild hyperphenylalaninemia, 50.7% mild PKU, and 7.4% classic PKU, were followed up over ≤12 years. A total of 85 different genotypes were reported. With the exception of two splice variants, all of the most common mutations were reported to be associated with substantial residual Phe hydroxylase activity. Median Phe tolerance increased 3.9 times with BH4/sapropterin therapy, compared with dietary treatment, and median Phe blood concentrations were within the therapeutic range in all patients. Compared with diet alone, improvement in quality of life was reported in 49.6% of patients, improvement in adherence to diet was reported in 47% of patients, and improvement in adherence to treatment was reported in 63.3% of patients. No severe adverse events were reported. CONCLUSIONS Our data document a long-term beneficial effect of orally administered BH4/sapropterin in responsive PKU patients by improving the metabolic control, increasing daily tolerance for dietary Phe intake, and for some, by improving dietary adherence and quality of life. Patient genotypes help in predicting BH4 responsiveness.
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Affiliation(s)
- Stefanie Keil
- Division of Inborn Metabolic Diseases, University Children's Hospital, Heidelberg, Germany
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Cerone R, Andria G, Giovannini M, Leuzzi V, Riva E, Burlina A. Testing for tetrahydrobiopterin responsiveness in patients with hyperphenylalaninemia due to phenylalanine hydroxylase deficiency. Adv Ther 2013; 30:212-28. [PMID: 23436109 DOI: 10.1007/s12325-013-0011-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Pharmacological levels of the phenylalanine hydroxylase enzyme cofactor, tetrahydrobiopterin (BH4), reduce plasma phenylalanine levels in some patients with phenylketonuria (PKU), providing the first pharmacological therapy for PKU. Responsiveness to this therapy must be determined empirically through a BH4 loading test or trial. The authors have analyzed the loading tests currently in use in light of the numerous factors that can influence their results. Sapropterin dihydrochloride is a stable, synthetic form of BH4 approved for treatment of PKU in responsive patients. METHODS An expert panel identified evidence from published reports of clinical experience. Reports of research involving at least 25 patients and published in English were considered. RESULTS In all, 14 studies met both criteria; eight employing the sapropterin dihydrochloride preparation from Schircks Laboratories and six the sapropterin dihydrochloride preparation from Biomarin/Merck Serono. CONCLUSION The arbitrary responsiveness definition of a >30% reduction in blood phenylalanine appears to be a good compromise between sensitivity and specificity for the initial screening test. However, individual patient characteristics should be considered when interpreting results, especially in patients with low baseline phenylalanine levels.
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Affiliation(s)
- Roberto Cerone
- Reference Center for Neonatal Screening and Diagnosis for Metabolic Diseases of University-Istituto Giannina Gaslini, Via 5 maggio, 3916147 Genoa, Italy.
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11
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Cunningham A, Bausell H, Brown M, Chapman M, DeFouw K, Ernst S, McClure J, McCune H, O'Steen D, Pender A, Skrabal J, Wessel A, Jurecki E, Shediac R, Prasad S, Gillis J, Cederbaum S. Recommendations for the use of sapropterin in phenylketonuria. Mol Genet Metab 2012; 106:269-76. [PMID: 22575621 DOI: 10.1016/j.ymgme.2012.04.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 04/05/2012] [Accepted: 04/05/2012] [Indexed: 11/18/2022]
Abstract
Phenylketonuria (PKU) is an inherited disorder of phenylalanine (Phe) metabolism. Until recently, the only treatment for PKU was a Phe-restricted diet. Increasing evidence of suboptimal outcomes in diet-treated individuals, inconsistent PKU management practices, and the recent availability of tetrahydrobiopterin (BH(4)) therapy have fueled the need for new management and treatment recommendations for this metabolic disorder. BH(4), now available as sapropterin dihydrochloride (sapropterin), may offer the potential for improved metabolic control as well as enhanced dietary Phe tolerance in some PKU patients. A group of metabolic dietitians from North America convened in June 2011 to draft recommendations for the use of sapropterin therapy in PKU. Physicians with extensive experience in PKU management were invited at a later date to contribute to the development of these recommendations. Based on extensive clinical experience and current evidence, the present recommendations provide guidance from patient selection and determination of sapropterin response to the long-term management of patients on sapropterin therapy. Target Phe levels, nutritional adequacy, neurocognitive screening and adherence to treatment are addressed to optimize patient outcomes.
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