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Elhawary NA, AlJahdali IA, Abumansour IS, Elhawary EN, Gaboon N, Dandini M, Madkhali A, Alosaimi W, Alzahrani A, Aljohani F, Melibary EM, Kensara OA. Genetic etiology and clinical challenges of phenylketonuria. Hum Genomics 2022; 16:22. [PMID: 35854334 PMCID: PMC9295449 DOI: 10.1186/s40246-022-00398-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/08/2022] [Indexed: 02/08/2023] Open
Abstract
This review discusses the epidemiology, pathophysiology, genetic etiology, and management of phenylketonuria (PKU). PKU, an autosomal recessive disease, is an inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene. The prevalence of PKU varies widely among ethnicities and geographic regions, affecting approximately 1 in 24,000 individuals worldwide. Deficiency in the PAH enzyme or, in rare cases, the cofactor tetrahydrobiopterin results in high blood Phe concentrations, causing brain dysfunction. Untreated PKU, also known as PAH deficiency, results in severe and irreversible intellectual disability, epilepsy, behavioral disorders, and clinical features such as acquired microcephaly, seizures, psychological signs, and generalized hypopigmentation of skin (including hair and eyes). Severe phenotypes are classic PKU, and less severe forms of PAH deficiency are moderate PKU, mild PKU, mild hyperphenylalaninaemia (HPA), or benign HPA. Early diagnosis and intervention must start shortly after birth to prevent major cognitive and neurological effects. Dietary treatment, including natural protein restriction and Phe-free supplements, must be used to maintain blood Phe concentrations of 120-360 μmol/L throughout the life span. Additional treatments include the casein glycomacropeptide (GMP), which contains very limited aromatic amino acids and may improve immunological function, and large neutral amino acid (LNAA) supplementation to prevent plasma Phe transport into the brain. The synthetic BH4 analog, sapropterin hydrochloride (i.e., Kuvan®, BioMarin), is another potential treatment that activates residual PAH, thus decreasing Phe concentrations in the blood of PKU patients. Moreover, daily subcutaneous injection of pegylated Phe ammonia-lyase (i.e., pegvaliase; PALYNZIQ®, BioMarin) has promised gene therapy in recent clinical trials, and mRNA approaches are also being studied.
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Affiliation(s)
- Nasser A. Elhawary
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Imad A. AlJahdali
- grid.412832.e0000 0000 9137 6644Department of Community Medicine, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Iman S. Abumansour
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Ezzeldin N. Elhawary
- grid.123047.30000000103590315Faculty of Medicine, MS Genomic Medicine Program, University of Southampton, Southampton General Hospital, Southampton, UK
| | - Nagwa Gaboon
- grid.7269.a0000 0004 0621 1570Department of Clinical Genetics, Faculty of Medicine, Ain Shams University, Cairo, Egypt
| | - Mohammed Dandini
- Department of Laboratory and Blood Bank, Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Abdulelah Madkhali
- grid.415254.30000 0004 1790 7311Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Saudi Arabia
| | - Wafaa Alosaimi
- Department of Hematology, Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Abdulmajeed Alzahrani
- Department of Laboratory and Blood Bank at Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Fawzia Aljohani
- Department of Pediatric Clinics, Maternity and Children Hospital, King Salman Medical City, Madinah, Saudi Arabia
| | - Ehab M. Melibary
- grid.412832.e0000 0000 9137 6644Department of Medical Genetics, College of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955 Saudi Arabia
| | - Osama A. Kensara
- grid.412832.e0000 0000 9137 6644Department of Clinical Nutrition, Faculty of Applied Medical Sciences, Umm Al-Qura University, Jeddah, Saudi Arabia
- Department of Biochemistry, Batterjee Medical College, Jeddah, Saudi Arabia
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Guibal P, Lo A, Maitre P, Moussa F. Pterin determination in cerebrospinal fluid: state of the art. Pteridines 2017. [DOI: 10.1515/pterid-2017-0001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
The analysis of pterins in the cerebrospinal fluid (CSF) is mandatory for the etiologic diagnosis of inborn errors of dopamine and serotonin metabolism. The success of the available therapeutic strategies for preventing the ongoing brain dysfunction is tightly dependent of the early diagnosis of these neurotransmitter disorders. Previous methods of pterins determination in the CSF have in common at least one reversed phase HPLC step coupled to electrochemical or fluorescence detection (FD). They differ in the oxidation procedure of the reduced forms of pterins into their oxidized fluorescent counterparts. Most of the methods using the FD include at least one offline chemical oxidation procedure and cannot allow the direct quantification of tetrahydrobiopterin (BH4). A recent method proposed a single step simultaneous quantification of all forms of pterins including BH4 by HPLC coupled to FD after post-column coulometric oxidation. Nowadays, recent advances in mass spectrometry (MS), notably in term of sensitivity, allow the direct unambiguous determination of all forms of pterins in the CSF by LC-MS/MS.
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Affiliation(s)
- Pierre Guibal
- Letiam, Lip(Sys) , Université Paris-Sud , IUT d’Orsay, Plateau de Moulon , 91405 Orsay , France
| | - Aurélien Lo
- Letiam, Lip(Sys) , Université Paris-Sud , IUT d’Orsay, Plateau de Moulon , 91405 Orsay , France
| | - Philippe Maitre
- Laboratoire de Chimie Physique , UMR 8000 CNRS , Faculté des Sciences d’Orsay, Université Paris-Sud , 15, Rue G. Clemenceau , 91400 Orsay , France
| | - Fathi Moussa
- Letiam, Lip(Sys) , Université Paris-Sud , IUT d’Orsay, Plateau de Moulon , 91405 Orsay , France
- Service de Biochimie, Groupe Hospitalier Trousseau-La Roche Guyon , APHP, 26 Avenue du Dr A. Netter , 75012 Paris , France
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Tansek MZ, Groselj U, Kelvisar M, Kobe H, Lampret BR, Battelino T. Long-term BH4 (sapropterin) treatment of children with hyperphenylalaninemia - effect on median Phe/Tyr ratios. J Pediatr Endocrinol Metab 2016; 29:561-6. [PMID: 26910740 DOI: 10.1515/jpem-2015-0337] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/30/2015] [Indexed: 11/15/2022]
Abstract
BACKGROUND Phenylalanine hydroxylase deficiency causes various degrees of hyperphenylalaninemia (HPA). Tetrahydrobiopterin (BH4; sapropterin) reduces phenylalanine (Phe) levels in responders, enabling relaxation of dietary therapy. We aimed to assess long-term effects of BH4 treatment in HPA patients. METHODS Nine pre-pubertal BH4 responsive children were treated with BH4 for at least 2 years. The median dietary tolerance to Phe and levels of blood Phe, tyrosine (Tyr), zinc, selenium and vitamin B12 and anthropometric measurements, in the 2 years periods before and after the introduction of BH4 treatment were analyzed and compared. Adverse effects of BH4 were assessed. RESULTS The daily Phe tolerance had tripled, from pretreatment median value of 620 mg (IQR 400-700 mg) to 2000 (IQR 1000-2000 mg) after 2 years of follow up (p<0.001). The median blood Phe levels during the 2 years period before introducing BH4 did not change significantly during the 2 years on therapy (from 200 μmol/L; IQR 191-302 to 190 μmol/L; IQR 135-285 μmol/L), but the median blood Phe/Tyr ratio had lowered significantly from pre-treatment value 4.7 to 2.4 during the 2 years on therapy (p=0.01). Median zinc, selenium, vitamin B12 levels and anthropometric measurements did not change while on BH4 therapy (p=NS). No adverse effects were noticed. CONCLUSIONS BH4 therapy enabled patients much higher dietary Phe intakes, with no noticeable adverse effects. Median blood Phe and Tyr levels, median zinc, selenium, vitamin B12 levels and anthropometric measurements did not change significantly on BH4 therapy, but median Phe/Tyr ratios had lowered.
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Abstract
BACKGROUND Phenylketonuria results from a deficiency of the enzyme phenylalanine hydroxylase. Dietary restriction of phenylalanine keeps blood phenylalanine concentration low. Most natural foods are excluded from diet and supplements are used to supply other nutrients. Recent publications report a decrease in blood phenylalanine concentration in some patients treated with sapropterin dihydrochloride. We examined the evidence for the use of sapropterin dihydrochloride to treat phenylketonuria. This is an update of a previously published Cochrane Review. OBJECTIVES To assess the safety and efficacy of sapropterin dihydrochloride in lowering blood phenylalanine concentration in people with phenylketonuria. SEARCH METHODS We identified relevant trials from the Group's Inborn Errors of Metabolism Trials Register. Date of last search: 11 August 2014.We also searched ClinicalTrials.gov and Current controlled trials. Last search: 4 September 2014We contacted the manufacturers of the drug (BioMarin Pharmaceutical Inc.) for information regarding any unpublished trials. SELECTION CRITERIA Randomized controlled trials comparing sapropterin with no supplementation or placebo in people with phenylketonuria due to phenylalanine hydroxylase deficiency. DATA COLLECTION AND ANALYSIS Two authors independently assessed trials and extracted outcome data. MAIN RESULTS Two placebo-controlled trials were included. One trial administered 10 mg/kg/day sapropterin in 89 children and adults with phenylketonuria whose diets were not restricted and who had previously responded to saproterin.This trial measured change in blood phenylalanine concentration. The second trial screened 90 children (4 to 12 years) with phenylketonuria whose diet was restricted, for responsiveness to sapropterin. Forty-six responders entered the placebo-controlled part of the trial and received 20 mg/kg/day sapropterin. This trial measured change in both phenylalanine concentration and protein tolerance. Both trials reported adverse events. The trials showed an overall low risk of bias; but both are Biomarin-sponsored. One trial showed a significant lowering in blood phenylalanine concentration in the sapropterin group (10 mg/kg/day), mean difference -238.80 μmol/L (95% confidence interval -343.09 to -134.51); a second trial (20 mg/kg/day sapropterin) showed a non-significant difference, mean difference -51.90 μmol/L (95% confidence interval -197.27 to 93.47). The second trial also reported a significant increase in phenylalanine tolerance, mean difference18.00 mg/kg/day (95% confidence interval 12.28 to 23.72) in the 20 mg/kg/day sapropterin group. AUTHORS' CONCLUSIONS There is evidence of short-term benefit from using sapropterin in some people with sapropterin-responsive forms of phenylketonuria; blood phenylalanine concentration is lowered and protein tolerance increased. There are no serious adverse events associated with using sapropterin in the short term.There is no evidence on the long-term effects of sapropterin and no clear evidence of effectiveness in severe phenylketonuria.
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Affiliation(s)
- Usha Rani Somaraju
- Malla Reddy Medical College for WomenDepartment of BiochemistrySuraram Main RoadJeedimetla Qutbullapur MunicipalityHyderabadIndia500 055
| | - Marcus Merrin
- American University of Antigua / Manipan Education AmericasIT1 Battery Park Plaza33rd FloorNew YorkNYUSA10004
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Guibal P, Lévêque N, Doummar D, Giraud N, Roze E, Rodriguez D, Couderc R, Billette
De Villemeur T, Moussa F. Simultaneous determination of all forms of biopterin and neopterin in cerebrospinal fluid. ACS Chem Neurosci 2014; 5:533-41. [PMID: 24650440 PMCID: PMC4102970 DOI: 10.1021/cn4001928] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 03/16/2014] [Indexed: 11/29/2022] Open
Abstract
In humans, genetic defects of the synthesis or regeneration of tetrahydrobiopterin (BH4), an essential cofactor in hydroxylation reactions, are associated with severe neurological disorders. The diagnosis of these conditions relies on the determination of BH4, dihydrobiopterin (BH2), and dihydroneopterin (NH2) in cerebrospinal fluid (CSF). As MS/MS is less sensitive than fluorescence detection (FD) for this purpose, the most widely used method since 1980 involves two HPLC runs including two differential off-line chemical oxidation procedures aiming to transform the reduced pterins into their fully oxidized fluorescent counterparts, biopterin (B) and neopterin (N). However, this tedious and time-consuming two-step indirect method underestimates BH4, BH2, and NH2 concentrations. Direct quantification of BH4 is essential for studying its metabolism and for monitoring the efficacy of BH4 supplementation in patients with genetic defects. Here we describe a single step method to simultaneously measure BH4, BH2, B, NH2, and N in CSF by HPLC coupled to FD after postcolumn coulometric oxidation. All target pterins were quantified in CSF with a small volume (100 μL), and a single filtration step for sample preparation and analysis. As compared to the most widely used method in more than 100 CSF samples, this new assay is the easiest route for accurately determining in a single run BH4, BH2, and NH2 in CSF in deficit situations as well as for monitoring the efficacy of the treatment.
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Affiliation(s)
- Pierre Guibal
- LETIAM, GCAPS,
EA 4041, IUT d’Orsay, Université Paris Sud 11, Plateau de Moulon. 91400 Orsay, France
| | - Nathalie Lévêque
- LETIAM, GCAPS,
EA 4041, IUT d’Orsay, Université Paris Sud 11, Plateau de Moulon. 91400 Orsay, France
| | - Diane Doummar
- Services
de Neuropédiatrie
et de Biochimie, Groupe Hospitalier Trousseau − Laroche −
Guyon, 26 avenue du Dr Arnold Netter, 75012 Paris, France
| | - Nicolas Giraud
- UMR CNRS
8182. ICMMO:
RMN en milieu orienté. UFR des Sciences, Université
Paris Sud 11. Rue du Doyen Georges
Poitou. 91400 Orsay, France
| | - Emmanuel Roze
- Department
of Neurology, Pitié-Salpêtrière
Hospital, AP-HP, 75013 Paris, France
- UMR S 952, INSERM,
Paris 6 University, 75005 Paris, France
| | - Diana Rodriguez
- Services
de Neuropédiatrie
et de Biochimie, Groupe Hospitalier Trousseau − Laroche −
Guyon, 26 avenue du Dr Arnold Netter, 75012 Paris, France
| | - Rémy Couderc
- Services
de Neuropédiatrie
et de Biochimie, Groupe Hospitalier Trousseau − Laroche −
Guyon, 26 avenue du Dr Arnold Netter, 75012 Paris, France
| | - Thierry Billette
De Villemeur
- Services
de Neuropédiatrie
et de Biochimie, Groupe Hospitalier Trousseau − Laroche −
Guyon, 26 avenue du Dr Arnold Netter, 75012 Paris, France
| | - Fathi Moussa
- LETIAM, GCAPS,
EA 4041, IUT d’Orsay, Université Paris Sud 11, Plateau de Moulon. 91400 Orsay, France
- Services
de Neuropédiatrie
et de Biochimie, Groupe Hospitalier Trousseau − Laroche −
Guyon, 26 avenue du Dr Arnold Netter, 75012 Paris, France
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Abstract
BACKGROUND Phenylketonuria results from a deficiency of the enzyme phenylalanine hydroxylase. Dietary restriction of phenylalanine keeps blood phenylalanine concentration low. Most natural foods are excluded from diet and supplements are used to supply other nutrients. Recent publications report a decrease in blood phenylalanine concentration in some patients treated with sapropterin dihydrochloride. We examined the evidence for the use of sapropterin dihydrochloride to treat phenylketonuria. OBJECTIVES To assess the safety and efficacy of sapropterin dihydrochloride in lowering blood phenylalanine concentration in people with phenylketonuria. SEARCH METHODS We identified relevant trials from the Group's Inborn Errors of Metabolism Trials Register. Date of last search: 29 June 2012.We also searched ClinicalTrials.gov and Current controlled trials. Last search: 23 July 2012.We contacted the manufacturers of the drug (BioMarin Pharmaceutical Inc.) for information regarding any unpublished trials. SELECTION CRITERIA Randomized controlled trials comparing sapropterin with no supplementation or placebo in people with phenylketonuria due to phenylalanine hydroxylase deficiency. DATA COLLECTION AND ANALYSIS Two authors independently assessed trials and extracted outcome data. MAIN RESULTS Two placebo-controlled trials were included. One trial administered 10 mg/kg/day sapropterin in 89 children and adults with phenylketonuria whose diets were not restricted and who had previously responded to saproterin.This trial measured change in blood phenylalanine concentration. The second trial screened 90 children (4 to 12 years) with phenylketonuria whose diet was restricted, for responsiveness to sapropterin. Forty-six responders entered the placebo-controlled part of the trial and received 20 mg/kg/day sapropterin. This trial measured change in both phenylalanine concentration and protein tolerance. Both trials reported adverse events. The trials showed an overall low risk of bias; but both are Biomarin-sponsored. One trial showed a significant lowering in blood phenylalanine concentration in the sapropterin group (10 mg/kg/day), mean difference -238.80 μmol/L (95% confidence interval -343.09 to -134.51); a second trial (20 mg/kg/day sapropterin) showed a non-significant difference, mean difference -51.90 μmol/L (95% confidence interval -197.27 to 93.47). The second trial also reported a significant increase in phenylalanine tolerance, mean difference18.00 mg/kg/day (95% confidence interval 12.28 to 23.72) in the 20 mg/kg/day sapropterin group. AUTHORS' CONCLUSIONS There is evidence of short-term benefit from using sapropterin in some patients with sapropterin-responsive forms of phenylketonuria; blood phenylalanine concentration is lowered and protein tolerance increased. There are no serious adverse events associated with using sapropterin in the short term.There is no evidence on the long-term effects of sapropterin and no clear evidence of effectiveness in severe phenylketonuria.
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Affiliation(s)
- Usha Rani Somaraju
- Department of Biochemistry and Genetics, Trinity School of Medicine, Kingstown, Saint Vincent and The Grenadines.
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Tansek MZ, Groselj U, Murko S, Kobe H, Lampret BR, Battelino T. Assessment of tetrahydrobiopterin (BH(4))-responsiveness and spontaneous phenylalanine reduction in a phenylalanine hydroxylase deficiency population. Mol Genet Metab 2012; 107:37-42. [PMID: 22917871 DOI: 10.1016/j.ymgme.2012.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 07/13/2012] [Accepted: 07/13/2012] [Indexed: 11/28/2022]
Abstract
A BH(4) loading test was performed in 36 patients from 34 unrelated families. The patients had 29 different genotypes, and previous data on only eight of them were found in the BIOPKU database. Thirteen patients were classified as classic PKU (35.1%), 14 as mild PKU (37.8%) and 9 as MHP (27.0%). Blood Phe levels were shown to reach a plateau after three full days of increased natural protein ingestion. Measuring the 24-hour blood Phe levels (T(-24), T(-16), T(0)) on the fourth day of increased protein ingestion before BH(4) administration showed that within 24h Phe on average increased by 2.4% in MHP patients, decreased by 2.7% in mild PKU patients and increased by 9.7% in classic PKU patients (NS for all comparisons); Phe only slightly decreased in responders by 0.2% but increased in non-responders by 7.8% (P>0.05). Altogether, 16 of 36 (44.4%) patients represented by 12 of 29 (41.4%) different genotypes were proven to be BH(4) responders, and four (10.8%) were slow-responders. Responders were 6/9 (66.7%) MHP patients, 10/14 (71.4%) mild PKU patients and 0/13 classic PKU patients. Twenty of the 29 (68.9%) genotypes harbored at least one mutation with a known PRA of 10% or more but only 11 (55%) of them were BH(4)-responsive. Spontaneous reduction of blood Phe levels within 24h on the fourth day of natural protein loading was observed only in mild PKU patients and was shown not to be an important part of the BH(4)-response. 73.3% of genotypes containing at least one allele with a PRA of at least 30% were found to be BH(4) responsive; a PRA of at least 15.5% was needed for the responder genotype in our population.
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Affiliation(s)
- Mojca Zerjav Tansek
- Department of Pediatric Endocrinology, Diabetes and Metabolic Diseases, University Children's Hospital, UMC Ljubljana, Ljubljana, Slovenia
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8
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Bélanger-Quintana A, Burlina A, Harding CO, Muntau AC. Up to date knowledge on different treatment strategies for phenylketonuria. Mol Genet Metab 2011; 104 Suppl:S19-25. [PMID: 21967857 PMCID: PMC4437510 DOI: 10.1016/j.ymgme.2011.08.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 07/23/2011] [Accepted: 08/05/2011] [Indexed: 11/18/2022]
Abstract
Dietary management for phenylketonuria was established over half a century ago, and has rendered an immense success in the prevention of the severe mental retardation associated with the accumulation of phenylalanine. However, the strict low-phenylalanine diet has several shortcomings, not the least of which is the burden it imposes on the patients and their families consequently frequent dietary non-compliance. Imperfect neurological outcome of patients in comparison to non-PKU individuals and nutritional deficiencies associated to the PKU diet are other important reasons to seek alternative therapies. In the last decade there has been an impressive effort in the investigation of other ways to treat PKU that might improve the outcome and quality of life of these patients. These studies have lead to the commercialization of sapropterin dihydrochloride, but there are still many questions regarding which patients to challenge with sapropterin what is the best challenge protocol and what could be the implications of this treatment in the long-term. Current human trials of PEGylated phenylalanine ammonia lyase are underway, which might render an alternative to diet for those patients non-responsive to sapropterin dihydrochloride. Preclinical investigation of gene and cell therapies for PKU is ongoing. In this manuscript, we will review the current knowledge on novel pharmacologic approaches to the treatment of phenylketonuria.
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Affiliation(s)
- Amaya Bélanger-Quintana
- Division of Metabolic Diseases, Pediatrics Department, Ramon y Cajal Hospital, Madrid, Spain.
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Jessup JA, Zhang L, Presley TD, Kim-Shapiro DB, Wang H, Chen AF, Groban L. Tetrahydrobiopterin restores diastolic function and attenuates superoxide production in ovariectomized mRen2.Lewis rats. Endocrinology 2011; 152:2428-36. [PMID: 21427216 PMCID: PMC3100612 DOI: 10.1210/en.2011-0061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 03/02/2011] [Indexed: 02/06/2023]
Abstract
After oophorectomy, mRen2.Lewis rats exhibit diastolic dysfunction associated with elevated superoxide, increased cardiac neuronal nitric oxide synthase (nNOS) expression, and diminished myocardial tetrahydrobiopterin (BH₄) content, effects that are attenuated with selective nNOS inhibition. BH₄ is an essential cofactor of nNOS catalytic activity leading to nitric oxide production. Therefore, we assessed the effect of 4 wk BH₄ supplementation on diastolic function and left ventricular (LV) remodeling in oophorectomized mRen2.Lewis rats compared with sham-operated controls. Female mRen2.Lewis rats underwent either bilateral ovariectomy (OVX) (n = 19) or sham operation (n = 13) at 4 wk of age. Beginning at 11 wk of age, OVX rats were randomized to receive either BH₄ (10 mg/kg · d) or saline, whereas the sham rats received saline via sc mini-pumps. Loss of ovarian hormones reduced cardiac BH₄ when compared with control hearts; this was associated with impaired myocardial relaxation, augmented filling pressures, increased collagen deposition, and thickened LV walls. Additionally, superoxide production increased and nitric oxide decreased in hearts from OVX compared with sham rats. Chronic BH₄ supplementation after OVX improved diastolic function and attenuated LV remodeling while restoring myocardial nitric oxide release and preventing reactive oxygen species generation. These data indicate that BH₄ supplementation protects against the adverse effects of ovarian hormonal loss on diastolic function and cardiac structure in mRen2.Lewis rats by restoring myocardial NO release and mitigating myocardial O₂⁻ generation. Whether BH₄ supplementation is a therapeutic option for the management of diastolic dysfunction in postmenopausal women will require direct testing in humans.
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Affiliation(s)
- Jewell A Jessup
- Department of Anesthesiology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1009, USA
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10
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Okano Y, Kudo S, Nishi Y, Sakaguchi T, Aso K. Molecular characterization of phenylketonuria and tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency in Japan. J Hum Genet 2011; 56:306-12. [PMID: 21307867 DOI: 10.1038/jhg.2011.10] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phenylketonuria (PKU) is a heterogeneous metabolic disorder caused by a deficiency in hepatic phenylalanine hydroxylase (PAH). On the basis of phenotype/genotype correlations, determination of phenylketonuric genotype is important for classification of the clinical phenotype and treatment of PKU, including tetrahydrobiopterin therapy. We characterized the genotypes of 203 Japanese patients with PKU and hyperphenylalaninemia using the following systems: (1) denaturing high-performance liquid chromatography with a GC-clamped primer; (2) direct sequencing; and, (3) multiplex ligation-dependent probe amplification. Of 406 mutant alleles, 390 (96%) were genotyped; 65 mutations were identified, including 22 new mutations. R413P, R241C, IVS4-1g>a, R111X and R243Q were prevalent mutations. Mutations prevalent in the Japanese cohort are also common in Korean and Northern Chinese populations, suggesting same origin. The spectrum of prevalent mutations was not significantly different among six Japanese districts, indicating that Japan comprises a relatively homogeneous ethnic group. We classified the mutations by clinical phenotypes and in vivo PAH activity and estimated the mutations with potential tetrahydrobiopterin (BH(4)) responsiveness. The frequency of BH(4) responsiveness based on the genotype was 29.1% in Japanese PKU patients. A catalog of PKU genotypes would be useful for predicting clinical phenotype, deciding on the subsequent treatment of PKU including BH(4) therapy, and genetic counseling in East Asia.
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Affiliation(s)
- Yoshiyuki Okano
- Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, Japan.
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Robbins IM, Hemnes AR, Gibbs JS, Christman BW, Howard L, Meehan S, Cabrita I, Gonzalez R, Oyler T, Zhao L, Du RH, Mendes LA, Wilkins MR. Safety of sapropterin dihydrochloride (6r-bh4) in patients with pulmonary hypertension. Exp Lung Res 2011; 37:26-34. [PMID: 21077779 DOI: 10.3109/01902148.2010.512972] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The authors investigated the safety of oral tetrahydrobiopterin (BH4), a cofactor for nitric oxide synthesis, as a novel treatment for pulmonary hypertension (PH). Eighteen patients with pulmonary arterial hypertension or inoperable chronic thromboembolic PH received sapropterin dihydrochloride (6R-BH4), the optically active form of BH4, in addition to treatment with sildenafil and/or endothelin receptor antagonists in an open-label, dose-escalation study. 6R-BH4 was administered starting at a dose of 2.5 mg/kg and increasing to 20 mg/kg over 8 weeks. Changes in markers of nitric oxide synthesis, inflammation and oxidant stress, as well as exercise capacity and cardiac function were measured. 6R-BH4 was well tolerated at all doses without systemic hypotension, even when given in combination with sildenafil. There was a small but significant reduction in plasma monocyte chemoattractant protein (MCP)-1 levels on 5 mg/kg. No significant changes in measures of nitric oxide synthesis or oxidant stress were observed. There was improvement in 6-minute walk distance, most significant at a dose of 5 mg/kg, from 379 ± 61 to 413 ± 57 m 414 ± 57 m (P = .002). Oral 6R-BH4 can be administered safely in doses up to 20 mg/kg daily to patients with PH. Further studies are needed to explore its therapeutic potential.
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Affiliation(s)
- Ivan M Robbins
- Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
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Harding CO. New era in treatment for phenylketonuria: Pharmacologic therapy with sapropterin dihydrochloride. Biologics 2010; 4:231-6. [PMID: 20714359 PMCID: PMC2921259 DOI: 10.2147/btt.s3015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Indexed: 12/03/2022]
Abstract
Oral administration of sapropterin hydrochloride, recently approved for use by the US Food and Drug Administration and the European Commission, is a novel approach for the treatment of phenylketonuria (PKU), one of the most common inborn errors of metabolism. PKU is caused by an inherited deficiency of the enzyme phenylalanine hydroxylase (PAH), and the pathophysiology of the disorder is related to chronic accumulation of the free amino acid phenylalanine in tissues. Contemporary therapy is based upon restriction of dietary protein intake, which leads to reduction of blood phenylalanine levels. This therapy is difficult to maintain throughout life, and dietary noncompliance is commonplace. Sapropterin dihydrochloride is a synthetic version of tetrahydrobiopterin, the naturally occurring pterin cofactor that is required for PAH-mediated phenylalanine hydroxylation. In a subset of individuals with PAH deficiency, sapropterin administration leads to reduction in blood phenylalanine levels independent of dietary protein. For these individuals, sapropterin is an effective novel therapy for PKU.
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Affiliation(s)
- Cary O Harding
- Departments of Molecular and Medical Genetics and Pediatrics, Oregon Health & Science University, Portland, Oregon, USA
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Abstract
BACKGROUND Phenylketonuria results from a deficiency of the enzyme phenylalanine hydroxylase. Dietary restriction of phenylalanine keeps blood phenylalanine concentration low. Most natural foods are excluded from diet and supplements are used to supply other nutrients. Recent publications report a decrease in blood phenylalanine concentration in some patients treated with sapropterin dihydrochloride. We examined the evidence for the use of sapropterin dihydrochloride to treat phenylketonuria. OBJECTIVES To assess the safety and efficacy of sapropterin dihydrochloride in lowering blood phenylalanine concentration in people with phenylketonuria. SEARCH STRATEGY We identified relevant trials from the Group's Inborn Errors of Metabolism Trials Register. Last search:07 May 2010.We also searched ClinicalTrials.gov and Current controlled trials. Last search: 01 September 2009.We contacted the manufacturers of the drug (BioMarin Pharmaceutical Inc.) for information regarding any unpublished trials. SELECTION CRITERIA Randomized controlled trials comparing sapropterin with no supplementation or placebo in people with phenylketonuria due to phenylalanine hydroxylase deficiency. DATA COLLECTION AND ANALYSIS Two authors independently assessed trials and extracted outcome data. MAIN RESULTS Two placebo-controlled trials were included. One trial administered 10 mg/kg/day sapropterin in 89 children and adults with phenylketonuria whose diets were not restricted and who had previously responded to saproterin.This trial measured change in blood phenylalanine concentration. The second trial screened 90 children (4 to 12 years) with phenylketonuria whose diet was restricted, for responsiveness to sapropterin. Forty-six responders entered the placebo-controlled part of the trial and received 20 mg/kg/day sapropterin. This trial measured change in both phenylalanine concentration and protein tolerance. Both trials reported adverse events. The trials showed an overall low risk of bias; but both are Biomarin-sponsored. One trial showed a significant lowering in blood phenylalanine concentration in the sapropterin group (10 mg/kg/day), mean difference -238.80 mumol/L (95% confidence interval -343.09 to -134.51); a second trial (20 mg/kg/day sapropterin) showed a non-significant difference, mean difference -51.90 mumol/L (95% confidence interval -197.27 to 93.47). The second trial also reported a significant increase in phenylalanine tolerance, mean difference18.00 mg/kg/day (95% confidence interval 12.28 to 23.72) in the 20 mg/kg/day sapropterin group. AUTHORS' CONCLUSIONS There is evidence of short-term benefit from using sapropterin in some patients with sapropterin-responsive forms of phenylketonuria; blood phenylalanine concentration is lowered and protein tolerance increased. There are no serious adverse events associated with using sapropterin in the short term.There is no evidence on the long-term effects of sapropterin and no clear evidence of effectiveness in severe phenylketonuria.
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Affiliation(s)
- Usha Rani Somaraju
- Department of Biochemistry and Genetics, Trinity School of Medicine, Harmony Hall, Prospect, Kingstown, St.Vincent, Saint Vincent and The Grenadines, P. O. Box 1669
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Burlina A, Blau N. Effect of BH(4) supplementation on phenylalanine tolerance. J Inherit Metab Dis 2009; 32:40-5. [PMID: 19067227 DOI: 10.1007/s10545-008-0947-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 10/13/2008] [Accepted: 10/20/2008] [Indexed: 11/29/2022]
Abstract
BACKGROUND Tetrahydrobiopterin (BH(4)) is a potential new orphan drug for the treatment of some patients with phenylketonuria (PKU), mostly mild forms. Numerous studies have confirmed this finding and BH(4)-responsiveness may be predicted to some extent from the corresponding genotype. AIM To investigate the response to BH(4) loading test, the phenylalanine hydroxylase (PAH) mutations and the long-term therapeutic efficacy of BH(4) in patients with PKU, and to better define BH(4)-responsive patients according to phenylalanine (Phe) levels and dietary phenylalanine tolerance. METHODS 30 Italian PKU patients (age range: 6 months-24 years; 12 female, 18 male) were included in this retrospective study. Eleven out of 30 patients presented with Phe levels below 450 micromol/L and 19 patients with Phe levels between 450 and 900 micromol/L. In the second group, we investigated the effect of long-term (6 months-7 years) oral administration of BH(4) on blood Phe levels and daily Phe tolerance. RESULTS In all patients with initial blood Phe levels <450 micromol/L (n = 11), BH(4) loading test was positive, but no treatment was introduced. In 12 out of 19 patients with blood Phe levels >450 micromol/L and positive at BH(4) loading, the treatment with BH(4) (10 mg/kg per day) was initiated. Before BH(4) treatment, Phe tolerance was less than 700 mg/day in all patients except for one (patient no. 9), increasing to 2-3-fold (from 498 +/- 49 to 1475 +/- 155 mg/day) on BH(4) treatment. In these patients the amino acid mixture supplementation was stopped and the diet was a combination of low-protein foods and natural proteins, mostly from animal sources. CONCLUSION Long-term BH(4) substitution (up to 7 years) in a group of moderate PKU patients allowed a substantial relaxation of the dietary restrictions or even replacement of the diet with BH(4) without any adverse effects.
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Affiliation(s)
- A Burlina
- Metabolic Unit, Division of Metabolic Diseases, Department of Pediatrics, University Hospital, Padua, Italy.
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Lee P, Treacy EP, Crombez E, Wasserstein M, Waber L, Wolff J, Wendel U, Dorenbaum A, Bebchuk J, Christ-Schmidt H, Seashore M, Giovannini M, Burton BK, Morris AA. Safety and efficacy of 22 weeks of treatment with sapropterin dihydrochloride in patients with phenylketonuria. Am J Med Genet A 2008; 146A:2851-9. [PMID: 18932221 DOI: 10.1002/ajmg.a.32562] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
Phenylketonuria (PKU) is an inherited metabolic disease characterized by phenylalanine (Phe) accumulation, which can lead to neurocognitive and neuromotor impairment. Sapropterin dihydrochloride, an FDA-approved synthetic formulation of tetrahydrobiopterin (6R-BH4, herein referred to as sapropterin) is effective in reducing plasma Phe concentrations in patients with hyperphenylalaninemia due to tetrahydrobiopterin (BH4)-responsive PKU, offering potential for improved metabolic control. Eighty patients, > or =8 years old, who had participated in a 6-week, randomized, placebo-controlled study of sapropterin, were enrolled in this 22-week, multicenter, open-label extension study comprising a 6-week forced dose-titration phase (5, 20, and 10 mg/kg/day of study drug consecutively for 2 weeks each), a 4-week dose-analysis phase (10 mg/kg/day), and a 12-week fixed-dose phase (patients received doses of 5, 10, or 20 mg/kg/day based on their plasma Phe concentrations during the dose titration). Dose-dependent reductions in plasma Phe concentrations were observed in the forced dose-titration phase. Mean (SD) plasma Phe concentration decreased from 844.0 (398.0) micromol/L (week 0) to 645.2 (393.4) micromol/L (week 10); the mean was maintained at this level during the study's final 12 weeks (652.2 [382.5] micromol/L at week 22). Sixty-eight (85%) patients had at least one adverse event (AE). All AEs, except one, were mild or moderate in severity. Neither the severe AE nor any of the three serious AEs was considered related to sapropterin. No AE led to treatment discontinuation. Sapropterin is effective in reducing plasma Phe concentrations in a dose-dependent manner and is well tolerated at doses of 5-20 mg/kg/day over 22 weeks in BH4-responsive patients with PKU.
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Affiliation(s)
- Phillip Lee
- National Hospital for Neurology & Neurosurgery, Charles Dent Metabolic Unit, Queen Square, London, UK
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16
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Feillet F, Chery C, Namour F, Kimmoun A, Favre E, Lorentz E, Battaglia-Hsu SF, Guéant JL. Evaluation of neonatal BH4 loading test in neonates screened for hyperphenylalaninemia. Early Hum Dev 2008; 84:561-7. [PMID: 18321666 DOI: 10.1016/j.earlhumdev.2008.01.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Revised: 12/12/2007] [Accepted: 01/07/2008] [Indexed: 10/22/2022]
Abstract
BACKGROUND The outcome in phenylketonuria is related to the early diagnosis and management due to neonatal screening. AIMS To assess the interest of tetrahydrobiopterin (BH4) loading test and phenylalanine hydroxylase (PAH) genotyping in the management of neonates with hyperphenylalaninemia (HPA). STUDY DESIGN We evaluate the effectiveness of a BH4 loading test (20 mg/kg) in ten neonates screened for HPA. We evaluated the time required to reach a target plasma Phenylalanine (Phe) level below 300 micromol/l. We compared these ten BH4-loaded patients to the 10 previous neonates non-loaded with BH4. In all these patients, the PAH genotype was determined. RESULTS One loaded patient had biopterin synthesis deficiency and has been retrieved from statistical analysis. All others patients have PAH deficiency. Between the BH4 loaded group (L) and the BH4 non-loaded group (NL), a statistically significant difference was observed in the average time required to reached the target Phe level (13.56 +/- 4.30 (L) vs. 20.6 +/- 7.59 days (NL) [p < 0.02]). Results of the genotyping from all but one of these 19 patients indicated that among all mutations present in this patient population, there were 4 known PAH mutations associated with BH4 responsiveness (p.R261Q, the p.V388 M, the p.E390G and the p.Y414C). These mutations were found in 4 non-loaded and 6 loaded patients. Two patients had a more than 90% reduction in their plasma Phe level within 24 h after the load. One of these patients had a PTPS deficiency. The other fully responsive patient (p.Y414C and IVS10-11G>A) has been treated with BH4 from birth with an excellent metabolic control for three years now. CONCLUSION BH4 loading test improves the management of HPA. It allows an immediate identification of the children fully responsive to BH4. Our results therefore suggest the incorporation of BH4 loading test in the management of neonates screened for HPA.
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Affiliation(s)
- François Feillet
- Reference Centre for Inborn Errors of Metabolism, Department of Pediatry, CHU of Nancy, Allée du Morvan, Vandoeuvre les Nancy, 54500, France.
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17
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Zurflüh MR, Zschocke J, Lindner M, Feillet F, Chery C, Burlina A, Stevens RC, Thöny B, Blau N. Molecular genetics of tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency. Hum Mutat 2008; 29:167-75. [PMID: 17935162 DOI: 10.1002/humu.20637] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Mutations in the phenylalanine hydroxylase (PAH) gene result in phenylketonuria (PKU). Tetrahydrobiopterin (BH(4))-responsive hyperphenylalaninemia has been recently described as a variant of PAH deficiency caused by specific mutations in the PAH gene. It has been suggested that BH(4)-responsiveness may be predicted from the corresponding genotypes. Data from BH(4) loading tests indicated an incidence of BH(4)-responsiveness of >40% in the general PKU population and >80% in mild PKU patients. The current project entailed genotype analysis of 315 BH(4)-responsive patients tabulated in the BIOPKUdb database and comparison with the data from the PAHdb locus-specific knowledgebase, as well as with previously published PAH mutations for several European countries, Northern China, and South Korea. We identified 57 mutations, presenting with a substantial residual PAH activity (average approximately 47%), presumed to be associated with BH(4)-responsiveness. More than 89% of patients are found to be compound heterozygotes. The three most common mutations found in >5% of BH(4)-responsive patients are p.A403 V, p.R261Q, and p.Y414C. Using the Hardy-Weinberg formula the predicted average frequency of BH(4)-responsiveness in European populations was calculated to be 55% (range 17-79%, lowest in Baltic countries and Poland and highest in Spain), 57% in Northern China, and 55% for South Korea. The genotype-predicted prevalence of BH(4)-responsiveness was higher than prevalence data obtained from BH(4) loading tests. Inconsistent results were observed for mutations p.L48S, p.I65 T, p.R158Q, p.R261Q, and p.Y414C. Our data suggest that BH(4)-responsiveness may be more common than assumed and to some extent may be predicted or excluded from the patient's genotype.
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Affiliation(s)
- Marcel R Zurflüh
- Division of Clinical Chemistry and Biochemistry, University Children's Hospital, Zürich, Switzerland
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18
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Burton BK, Grange DK, Milanowski A, Vockley G, Feillet F, Crombez EA, Abadie V, Harding CO, Cederbaum S, Dobbelaere D, Smith A, Dorenbaum A. The response of patients with phenylketonuria and elevated serum phenylalanine to treatment with oral sapropterin dihydrochloride (6R-tetrahydrobiopterin): a phase II, multicentre, open-label, screening study. J Inherit Metab Dis 2007; 30:700-7. [PMID: 17846916 DOI: 10.1007/s10545-007-0605-z] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 05/30/2007] [Accepted: 06/12/2007] [Indexed: 10/22/2022]
Abstract
This study aimed to evaluate the response to and safety of an 8-day course of sapropterin dihydrochloride (6R-tetrahydrobiopterin or 6R-BH4) 10 mg/kg per day in patients with phenylketonuria (PKU), who have elevated blood phenylalanine (Phe) levels, and to identify a suitable cohort of patients who would respond to sapropterin dihydrochloride treatment with a reduction in blood Phe level. Eligible patients were aged > or = 8 years, had blood Phe levels > or = 450 micromol/L and were not adhering to a Phe-restricted diet. Suitable patients were identified by a > or = 30% reduction in blood Phe level from baseline to day 8 following sapropterin dihydrochloride treatment. The proportion of patients who met these criteria was calculated for the overall population and by baseline Phe level (< 600, 600 to < 900, 900 to < 1200 and > or = 1200 micromol/L). In total, 485/490 patients completed the study and 20% (96/485) were identified as patients who would respond to sapropterin dihydrochloride. A reduction in Phe level was observed in all subgroups, although response was greater in patients with lower baseline Phe levels. Wide variability in response was seen across all baseline Phe subgroups. The majority of adverse events were mild and all resolved without complications. Sapropterin dihydrochloride was well tolerated and reduced blood Phe levels across all PKU phenotypes tested. Variability in reduction of Phe indicates that the response to sapropterin dihydrochloride cannot be predicted by baseline Phe level.
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Affiliation(s)
- B K Burton
- Children's Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60614, USA.
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Levy HL, Milanowski A, Chakrapani A, Cleary M, Lee P, Trefz FK, Whitley CB, Feillet F, Feigenbaum AS, Bebchuk JD, Christ-Schmidt H, Dorenbaum A. Efficacy of sapropterin dihydrochloride (tetrahydrobiopterin, 6R-BH4) for reduction of phenylalanine concentration in patients with phenylketonuria: a phase III randomised placebo-controlled study. Lancet 2007; 370:504-10. [PMID: 17693179 DOI: 10.1016/s0140-6736(07)61234-3] [Citation(s) in RCA: 224] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Early and strict dietary management of phenylketonuria is the only option to prevent mental retardation. We aimed to test the efficacy of sapropterin, a synthetic form of tetrahydrobiopterin (BH4), for reduction of blood phenylalanine concentration. METHODS We enrolled 89 patients with phenylketonuria in a Phase III, multicentre, randomised, double-blind, placebo-controlled trial. We randomly assigned 42 patients to receive oral doses of sapropterin (10 mg/kg) and 47 patients to receive placebo, once daily for 6 weeks. The primary endpoint was mean change from baseline in concentration of phenylalanine in blood after 6 weeks. Analysis was on an intention-to-treat basis. The study is registered with ClinicalTrials.gov, number NCT00104247. FINDINGS 88 of 89 enrolled patients received at least one dose of study drug, and 87 attended the week 6 visit. Mean age was 20 (SD 9.7) years. At baseline, mean concentration of phenylalanine in blood was 843 (300) micromol/L in patients assigned to receive sapropterin, and 888 (323) micromol/L in controls. After 6 weeks of treatment, patients given sapropterin had a decrease in mean blood phenylalanine of 236 (257) micromol/L, compared with a 3 (240) micromol/L increase in the placebo group (p<0.0001). After 6 weeks, 18/41 (44%) patients (95% CI 28-60) in the sapropterin group and 4/47 (9%) controls (95% CI 2-20) had a reduction in blood phenylalanine concentration of 30% or greater from baseline. Blood phenylalanine concentrations fell by about 200 micromol/L after 1 week in the sapropterin group and this reduction persisted for the remaining 5 weeks of the study (p<0.0001). 11/47 (23%) patients in the sapropterin group and 8/41 (20%) in the placebo group experienced adverse events that might have been drug-related (p=0.80). Upper respiratory tract infections were the most common disorder. INTERPRETATION In some patients with phenylketonuria who are responsive to BH4, sapropterin treatment to reduce blood phenylalanine could be used as an adjunct to a restrictive low-phenylalanine diet, and might even replace the diet in some instances.
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Affiliation(s)
- Harvey L Levy
- Children's Hospital Boston and Harvard Medical School, Boston, MA, USA.
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Fiege B, Blau N. Assessment of tetrahydrobiopterin (BH4) responsiveness in phenylketonuria. J Pediatr 2007; 150:627-30. [PMID: 17517248 DOI: 10.1016/j.jpeds.2007.02.017] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 01/09/2007] [Accepted: 02/01/2007] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To determine the prevalence of and identify subjects with phenylketonuria (PKU; phenylalanine hydroxylase deficiency) responsive to 6R-tetrahydrobiopterin (BH4) and to establish selection criteria for potential treatment with BH4. STUDY DESIGN Blood phenylalanine levels from 557 newborns and children with various degrees of PKU (blood phenylalanine, 301 to 4743 micromol/L) challenged with BH4 (20 mg/kg of body weight) were analyzed at 8 and 24 hours after BH4 administration. The 2 modalities were compared in terms of phenylalanine reduction. RESULTS The overall prevalence of BH4 responsiveness within patients with PKU for blood phenylalanine reductions of 20%, 30%, 40%, and 50% was 48%, 38%, 31%, and 24%, respectively, using the 8-hour modus and 55%, 46%, 41%, and 33%, respectively, using the 24-hour modus. Using the 30% cutoff, BH4 responsiveness was similar regardless of the modality in patients with mild hyperphenylalaninemia (79% to 83% responders), mild PKU (49% to 60% responders), and classical PKU (7% to 10% responders). CONCLUSIONS BH4 responsiveness is more prevalent than was previously assumed, particularly in patients with mild hyperphenylalaninemia and mild PKU. Depending on the severity of hyperphenylalaninemia, selection criteria for the potential treatment with BH4 may range from 20% to 40% blood phenylalanine reduction after 24 hours.
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Affiliation(s)
- Betina Fiege
- Division of Metabolism and Molecular Pediatrics, University Children's Hospital, Zurich, Switzerland
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Baldellou Vázquez A, Salazar García-Blanco MI, Ruiz-Echarri Zalaya MP, Campos Calleja C, Ruiz Desviat L, Ugarte Pérez M. [Tetrahydrobiopterin therapy for hyperphenylalaninemia due to phenylalanine hydroxylase deficiency. When and how?]. An Pediatr (Barc) 2006; 64:146-52. [PMID: 16527067 DOI: 10.1157/13084174] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
INTRODUCTION Some patients with hyperphenylalaninemia due to phenylalanine hydroxylase deficiency respond with a variable decrease in plasma phenylalanine levels after oral tetrahydrobiopterin (BH4) administration and are then able to tolerate higher dietary phenylalanine intake or even to discontinue a phenylalanine-restricted diet. BH4-sensitive patients are usually identified by means of a BH4 loading test, but consensus on the methodology of this test and the interpretation of its results is lacking. Consequently, a simple tool to identify which patients are likely candidates for this treatment and how they will progress in the long-term is required. MATERIAL AND METHODS A combined oral BH4 loading test with phenylalanine (100 mg/kg) and BH4 (20 mg/kg) was performed in 20 patients with hyperphenylalaninemia under dietary phenylalanine restriction. RESULTS Independently of the genotype, the result was positive in all the 9 patients whose maximum phenylalanine level at diagnosis was below 815 nmol/ml. Currently, they are under treatment with tetrahydrobiopterin doses of 7-15 mg/kg/day. All these patients have been able to increase their oral phenylalanine intake. Six are currently following a normal diet and the remaining three are close to reaching this goal. None of the patients with a maximum phenylalanine level at diagnosis higher than 938 nmol/ml responded to the BH4 loading test. CONCLUSIONS The maximum phenylalanine level at diagnosis seems to be a simple and reliable method to predict response to BH4 treatment. A high percentage of BH4-sensitive patients are able to discontinue a phenylalanine-restricted diet after long-term tetrahydrobiopterin treatment.
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Affiliation(s)
- A Baldellou Vázquez
- Unidad de Enfermedades Metabólicas, Hospital Infantil Miguel Servet, Zaragoza, Spain.
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22
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Bélanger-Quintana A, García MJ, Castro M, Desviat LR, Pérez B, Mejía B, Ugarte M, Martínez-Pardo M. Spanish BH4-responsive phenylalanine hydroxylase-deficient patients: evolution of seven patients on long-term treatment with tetrahydrobiopterin. Mol Genet Metab 2005; 86 Suppl 1:S61-6. [PMID: 16165389 DOI: 10.1016/j.ymgme.2005.07.024] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Revised: 07/06/2005] [Accepted: 07/06/2005] [Indexed: 11/28/2022]
Abstract
A novel subtype of patients with mutations in the phenylalanine hydroxylase (PAH) gene that show a positive response during a tetrahydrobiopterin (BH4) loading test has recently been recognized. These studies suggest that a number of phenylketonuric (PKU) patients may benefit from BH4 substitution, eliminating the need of life-long dietary restrictions. In our unit, we performed BH4 overload tests in 50 PAH-deficient patients. Overall, 38% of the patients had a positive response, mostly MHP and mild PKU patients, all with at least one missense mutation with presumed residual activity. Seven of the patients that required dietary restrictions have received treatment with BH4 from 5 to 18 months. All the patients included in the long-term treatment protocol had a mild PKU phenotype. BH4 therapy began at 10 mg/kg/day and changes were made over time depending on Phe levels. All patients at least doubled their protein ingestion and some could follow a completely free diet. Patients with a smaller decrease in Phe levels during the BH4 overload required higher BH4 doses and/or dietary restrictions to maintain adequate Phe levels over time. The genotype and the potential mechanisms underlying BH4 responsiveness and interindividual differences in pharmacokinetics of the administered cofactor are probably the basis for the differences in prolonged treatment.
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Affiliation(s)
- Amaya Bélanger-Quintana
- Unidad de Enfermedades Metabolicas, Servicio de Pediatría., Hospital Ramón y Cajal, Madrid, Spain.
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Hennermann JB, Bührer C, Blau N, Vetter B, Mönch E. Long-term treatment with tetrahydrobiopterin increases phenylalanine tolerance in children with severe phenotype of phenylketonuria. Mol Genet Metab 2005; 86 Suppl 1:S86-90. [PMID: 16051511 DOI: 10.1016/j.ymgme.2005.05.013] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2005] [Revised: 05/25/2005] [Accepted: 05/26/2005] [Indexed: 11/20/2022]
Abstract
Hyperphenylalaninemia caused by phenylalanine hydroxylase (PAH) deficiency requires lifelong rigorous diet starting in early infancy to prevent severe neurodevelopmental handicap. In a considerable number of children with mild hyperphenylalaninemia, long-term tetrahydrobiopterin (BH4) treatment significantly improves phenylalanine (phe) tolerance, but it has never been investigated in classic phenylketonuria (PKU). We performed a BH4-loading test in 40 consecutive infants with phe serum concentrations exceeding 240 microM, who had been detected by newborn screening programs. Eighteen out of 40 infants were found to be BH4 responsive. Five of them, responding to the neonatal BH4-loading test, showed a phe tolerance of less than 20 mg/kg/day and a phe pretreatment level of >1000 microM. They were treated with BH4 (20 mg/kg/day) over a period of 24 months. All five children had a sustained response to BH4, allowing substantial easing of dietary restrictions. Before BH4 treatment daily phe tolerance was 18-19 mg/kg, increasing to 30-80 mg/kg on BH4 treatment and decreasing again to 12-17 mg/kg after termination of BH4 treatment. Mutation analysis revealed compound heterozygosity for a putative null and a variant PAH mutation in four patients and homozygosity for a variant PAH mutation in one patient. We conclude that BH4 sensitivity is not restricted to mild hyperphenylalaninemia and that long-term BH4 treatment may also improve phenylalanine tolerance in a considerable number of children with a more severe PKU phenotype.
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Affiliation(s)
- Julia B Hennermann
- Otto Heubner Center for Pediatric and Adolescent Medicine, Charité University Medical Center, Campus Virchow-Klinikum, Berlin, Germany.
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Lambruschini N, Pérez-Dueñas B, Vilaseca MA, Mas A, Artuch R, Gassió R, Gómez L, Gutiérrez A, Campistol J. Clinical and nutritional evaluation of phenylketonuric patients on tetrahydrobiopterin monotherapy. Mol Genet Metab 2005; 86 Suppl 1:S54-60. [PMID: 16040265 DOI: 10.1016/j.ymgme.2005.05.014] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 05/24/2005] [Accepted: 05/25/2005] [Indexed: 10/25/2022]
Abstract
The clinical, nutritional, and neuropsychological data of 11 mild/moderate PKU patients after one year of treatment with BH4 are evaluated. BH4 monotherapy was introduced at 5 mg/kg/day in 14 PKU patients. In 11/14 patients, Phe tolerance increased significantly from 356+/-172 to 1546+/-192 mg/day (p=0.004), and special PKU formula was gradually reduced until complete removal. In them, mean plasma Phe concentrations remained below 360 micromol/L at 5 mg BH4/kg/day (7 mg/kg/day in one patient). BH4 therapy was stopped in three patients (V388M/P362T and R243Q/IVS10-11G>A genotypes) because it was not possible to improve Phe tolerance and to remove formula intake. Serum micronutrients were not significantly different at the start of treatment and at one year follow-up, except for selenium, which increased significantly after one year of therapy (p=0.017). Anthropometric, and nutritional measurements were within the age- and sex-specific percentiles for a healthy population after one year therapy. Neuropsychological follow-up indicated that intelligence scores persisted within normal limits. In terms of patients' genotype, we confirmed that the P275S mutation combined with R408W was associated with long-term BH4 responsiveness, while the combination of P362T/V388M, and R243Q/IVS10-11G>A resulted in poor metabolic control in long-term BH4 therapy. In summary, our data confirm that BH4 is a safe, and effective therapy in a selected group of mild, and moderate PKU patients who respond to the BH4 loading test. Low doses of BH4 in monotherapy permit withdrawal of the special formula and guarantee a good clinical and nutritional outcome with no adverse side effects in PKU patients.
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Affiliation(s)
- Nilo Lambruschini
- Nutrition Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Barcelona, Spain
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Kim SW, Jung J, Oh HJ, Kim J, Lee KS, Lee DH, Park C, Kimm K, Koo SK, Jung SC. Structural and functional analyses of mutations of the human phenylalanine hydroxylase gene. Clin Chim Acta 2005; 365:279-87. [PMID: 16253218 DOI: 10.1016/j.cca.2005.09.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 09/07/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND Phenylketonuria (PKU) is an inborn error of metabolism that results from a deficiency of phenylalanine hydroxylase (PAH). We demonstrated PAH mutational spectrum from patients with PKU, including 10 novel and 3 tetrahydrobiopterin (BH(4))-responsive mutations. In this study, 11 PAH missense mutations, including 6 novel mutations (P69S, G103S, L293M, G332V, S391I, A447P) found in our previous study, 2 mutations common in east Asian patients with PKU (R243Q, R413P), and 3 tetrahydrobiopterin (BH(4))-responsive mutations (R53H, R241C, R408Q) have been functionally and structurally analyzed. METHODS A transient protein overexpression system and an in vitro BH(4)-responsiveness study were used. The effects of PAH missense mutations on the PAH protein structure were also analyzed. To determine the conservation of 12 mutated residues, PAH was aligned using BLAST against full genomic sequences of 221 different species. Model structures of PAH protein and the composite tetramer were constructed using the software program, SHEBA. RESULTS No PAH activity was detected for some mutants. However, the residual activities associated with other mutants ranged over a wide spectrum. The missense mutations responsive to BH(4) were not highly conserved throughout the 43 species in the multiple sequence alignment that encode PAH. The composite model structure of PAH revealed that dimer stability was reduced in the BH(4)-responsive mutants, whereas tetramer stability remained normal. CONCLUSION This expression study analyzed PAH mutations and model structures of mutant PAH proteins are proposed. Correlation between the proposed mutant PAH structures and functions are suggested.
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Affiliation(s)
- Sang-Wun Kim
- Division of Genetic Disease, Department of Biomedical Sciences, National Institute of Health, Seoul, Republic of Korea
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Pérez-Dueñas B, Vilaseca MA, Mas A, Lambruschini N, Artuch R, Gómez L, Pineda J, Gutiérrez A, Mila M, Campistol J. Tetrahydrobiopterin responsiveness in patients with phenylketonuria. Clin Biochem 2004; 37:1083-90. [PMID: 15589814 DOI: 10.1016/j.clinbiochem.2004.09.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2004] [Accepted: 09/02/2004] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To investigate the BH4 response in a group of patients with phenylketonuria (PKU) in order to offer this alternative treatment to the responsive patients. DESIGN AND METHODS The 24-h-long Phe/BH4 loading test was performed on 64 PKU patients requiring dietary treatment. RESULTS All patients with mild-PKU and 75% of patients with moderate-PKU were BH4 responsive, while only 11% of classic-PKU patients showed good/partial response (P < 0.0001). The percentages of Phe decrease after the BH4 loading test were significantly different in the three PKU phenotypes (mild PKU: 67.9 +/- 18.7; moderate PKU: 37.4 +/- 16.8; and classical PKU: 21.9 +/- 13.7; ANOVA with Bonferroni correction: P < 0.0001). We report four mutations (P147S, D222G, P275S, and P362T) not previously associated with BH4 responsiveness, all of them combined with mutations with zero predicted residual activity. CONCLUSION Both the percentage of Phe decrease and the Phe value achieved 24 h after BH4 loading are valuable data in predicting a response. We report four mutations not previously associated with BH4 responsiveness.
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Affiliation(s)
- Belén Pérez-Dueñas
- Department of Neuropediatrics, Hospital Sant Joan de Déu, Universitat de Barcelona, Barcelona, Spain
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Blau N, Erlandsen H. The metabolic and molecular bases of tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency. Mol Genet Metab 2004; 82:101-11. [PMID: 15171997 DOI: 10.1016/j.ymgme.2004.03.006] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2004] [Revised: 03/23/2004] [Accepted: 03/23/2004] [Indexed: 11/28/2022]
Abstract
About two-thirds of all mild phenylketonuria (PKU) patients are tetrahydrobiopterin (BH4)-responsive and thus can be potentially treated with BH4 instead of a low-phenylalanine diet. Although there has been an increase in the amount of information relating to the diagnosis and treatment of this new variant of PKU, very little is know about the mechanisms of BH4-responsiveness. This review will focus on laboratory investigations and possible molecular and structural mechanisms involved in this process.
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Affiliation(s)
- Nenad Blau
- Division of Clinical Chemistry and Biochemistry, University Children's Hospital, Zurich, Switzerland.
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