Drug Delivery and Translational Research

, Volume 2, Issue 4, pp 223–237 | Cite as

Clinical therapeutics for phenylketonuria

  • Jaspreet Singh Kochhar
  • Sui Yung Chan
  • Pei Shi Ong
  • Lifeng Kang
Review Article


Phenylketonuria was amongst the first of the metabolic disorders to be characterised, exhibiting an inborn error in phenylalanine metabolism due to a functional deficit of the enzyme phenylalanine hydroxylase. It affects around 700,000 people around the globe. Mutations in the gene coding for hepatic phenylalanine hydroxylase cause this deficiency resulting in elevated plasma phenylalanine concentrations, leading to cognitive impairment, neuromotor disorders and related behavioural symptoms. Inception of low phenylalanine diet in the 1950s marked a revolution in the management of phenylketonuria and has since been a vital element of all therapeutic regimens. However, compliance to dietary therapy has been found difficult and newer supplement approaches are being examined. The current development of gene therapy and enzyme replacement therapeutics may offer promising alternatives for the management of phenylketonuria. This review outlines the pathological basis of phenylketonuria, various treatment regimes, their associated challenges and the future prospects of each approach. Briefly, novel drug delivery systems which can potentially deliver therapeutic strategies in phenylketonuria have been discussed.


Phenylketonuria Phenylalanine Hyperphenylalaninemia Phenylalanine hydroxylase Phenylalanine ammonia lyase 





Dihydropteridine reductase


Deoxyribonucleic acid


Enzyme Commission


European Medicines Agency




Enzyme Replacement Therapy


Food and Drug Administration




Guanosine triphosphate cyclohydrolase




Intelligence quotient


Large neutral amino acid


Online Mendelian Inheritance in Man


Phenylalanine hydroxylase


Phenylalanine ammonia lyase


Pterin-4a-carbinolamine dehydratase


Polyethylene glycol






Quinonoid dihydrobiopterin


Trans-cinnamic acid




  1. 1.
    Christ SE. Asbjorn Folling and the discovery of phenylketonuria. J Hist Neurosci. 2003;12(1):44–54.PubMedCrossRefGoogle Scholar
  2. 2.
    Kwok SC, Ledley FD, DiLella AG, Robson KJ, Woo SL. Nucleotide sequence of a full-length complementary DNA clone and amino acid sequence of human phenylalanine hydroxylase. Biochemistry. 1985;24(3):556–61.PubMedCrossRefGoogle Scholar
  3. 3.
    Scriver CR, Waters PJ, Sarkissian C, Ryan S, Prevost L, Cote D, et al. PAHdb: a locus-specific knowledgebase. Hum Mutat. 2000;15(1):99–104.PubMedCrossRefGoogle Scholar
  4. 4.
    Scriver CR, Hurtubise M, Konecki D, Phommarinh M, Prevost L, Erlandsen H, et al. PAHdb 2003: what a locus-specific knowledgebase can do. Hum Mutat. 2003;21(4):333–44.PubMedCrossRefGoogle Scholar
  5. 5.
    Kaufman S. A model of human phenylalanine metabolism in normal subjects and in phenylketonuric patients. Proc Natl Acad Sci USA. 1999;96(6):3160–4.PubMedCrossRefGoogle Scholar
  6. 6.
    Daubner SC, Le T, Wang S. Tyrosine hydroxylase and regulation of dopamine synthesis. Arch Biochem Biophys. 2011;508(1):1–12.PubMedCrossRefGoogle Scholar
  7. 7.
    Kim W, Erlandsen H, Surendran S, Stevens RC, Gamez A, Michols-Matalon K, et al. Trends in enzyme therapy for phenylketonuria. Mol Ther. 2004;10(2):220–4.PubMedCrossRefGoogle Scholar
  8. 8.
    de Baulny HO, Abadie V, Feillet F, de Parscau L. Management of phenylketonuria and hyperphenylalaninemia. J Nutr. 2007;137(6 Suppl 1):1561S–3S. discussion 1573S–1575S.PubMedGoogle Scholar
  9. 9.
    Harding CO. Progress toward cell-directed therapy for phenylketonuria. Clin Genet. 2008;74(2):97–104.PubMedCrossRefGoogle Scholar
  10. 10.
    Heintz C, Troxler H, Martinez A, Thony B, Blau N. Quantification of phenylalanine hydroxylase activity by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry. Mol Genet Metab. 2012;105(4):559–65.PubMedCrossRefGoogle Scholar
  11. 11.
    Thony B, Blau N. Mutations in the BH4-metabolizing genes GTP cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase, sepiapterin reductase, carbinolamine-4a-dehydratase, and dihydropteridine reductase. Hum Mutat. 2006;27(9):870–8.PubMedCrossRefGoogle Scholar
  12. 12.
    Sarkissian CN, Scriver CR, Mamer OA. Measurement of phenyllactate, phenylacetate, and phenylpyruvate by negative ion chemical ionization-gas chromatography/mass spectrometry in brain of mouse genetic models of phenylketonuria and non-phenylketonuria hyperphenylalaninemia. Anal Biochem. 2000;280(2):242–9.PubMedCrossRefGoogle Scholar
  13. 13.
    Eavri R, Lorberboum-Galski H. Novel approaches to the therapy of phenylketonuria. Ann Nestle. 2010;68(2):70–7.Google Scholar
  14. 14.
    Sanayama Y, Okano Y, Nagasaka H, Takayanagi M, Ohura T, Sakamoto O, et al. Experimental evidence that phenylalanine is strongly associated to oxidative stress in adolescents and adults with phenylketonuria. Mol Genet Metab. 2011;103(3):220–5.PubMedCrossRefGoogle Scholar
  15. 15.
    Williams RA, Mamotte CD, Burnett JR. Phenylketonuria: an inborn error of phenylalanine metabolism. Clin Biochem Rev. 2008;29(1):31–41.PubMedGoogle Scholar
  16. 16.
    van Spronsen FJ. Phenylketonuria: a 21st century perspective. Nat Rev Endocrinol. 2010;6(9):509–14.PubMedCrossRefGoogle Scholar
  17. 17.
    Anonymous. Recommendations on the dietary management of phenylketonuria. Report of Medical Research Council Working Party on Phenylketonuria. Arch Dis Child. 1993;68(3):426–7.Google Scholar
  18. 18.
    Burgard P, Bremer HJ, Buhrdel P, Clemens PC, Monch E, Przyrembel H, et al. Rationale for the German recommendations for phenylalanine level control in phenylketonuria 1997. Eur J Pediatr. 1999;158(1):46–54.PubMedCrossRefGoogle Scholar
  19. 19.
    Schweitzer-Krantz S, Burgard P. Survey of national guidelines for the treatment of phenylketonuria. Eur J Pediatr. 2000;159 Suppl 2:S70–3.PubMedCrossRefGoogle Scholar
  20. 20.
    Feillet F, van Spronsen FJ, MacDonald A, Trefz FK, Demirkol M, Giovannini M, et al. Challenges and pitfalls in the management of phenylketonuria. Pediatrics. 2010;126(2):333–41.PubMedCrossRefGoogle Scholar
  21. 21.
    Blau N, van Spronsen FJ, Levy HL. Phenylketonuria. Lancet. 2010;376(9750):1417–27.PubMedCrossRefGoogle Scholar
  22. 22.
    Bickel H, Gerrard J, Hickmans EM. Influence of phenylalanine intake on phenylketonuria. Lancet. 1953;265(6790):812.Google Scholar
  23. 23.
    Guthrie R, Susi A. A simple phenylalanine method for detecting phenylketonuria in large populations of newborn infants. Pediatrics. 1963;32:338–43.PubMedGoogle Scholar
  24. 24.
    Bodamer OA. Screening for phenylketonuria. Ann Nestle. 2010;68(2):53–7.Google Scholar
  25. 25.
    Millington DS, Kodo N, Norwood DL, Roe CR. Tandem mass spectrometry: a new method for acylcarnitine profiling with potential for neonatal screening for inborn errors of metabolism. J Inherit Metab Dis. 1990;13(3):321–4.PubMedCrossRefGoogle Scholar
  26. 26.
    Levy H, Burton B, Cederbaum S, Scriver C. Recommendations for evaluation of responsiveness to tetrahydrobiopterin (BH(4)) in phenylketonuria and its use in treatment. Mol Genet Metab. 2007;92(4):287–91.PubMedCrossRefGoogle Scholar
  27. 27.
    Blau N, Belanger-Quintana A, Demirkol M, Feillet F, Giovannini M, MacDonald A, et al. Optimizing the use of sapropterin (BH(4)) in the management of phenylketonuria. Mol Genet Metab. 2009;96(4):158–63.PubMedCrossRefGoogle Scholar
  28. 28.
    Ponzone A, Guardamagna O, Spada M, Ferraris S, Ponzone R, Kierat L, et al. Differential diagnosis of hyperphenylalaninaemia by a combined phenylalanine-tetrahydrobiopterin loading test. Eur J Pediatr. 1993;152(8):655–61.PubMedCrossRefGoogle Scholar
  29. 29.
    Blau N, Hennermann JB, Langenbeck U, Lichter-Konecki U. Diagnosis, classification, and genetics of phenylketonuria and tetrahydrobiopterin (BH4) deficiencies. Mol Genet Metab. 2011;104(Suppl):S2–9.PubMedCrossRefGoogle Scholar
  30. 30.
    Jaggi L, Zurfluh MR, Schuler A, Ponzone A, Porta F, Fiori L, et al. Outcome and long-term follow-up of 36 patients with tetrahydrobiopterin deficiency. Mol Genet Metab. 2008;93(3):295–305.PubMedCrossRefGoogle Scholar
  31. 31.
    Millington DS, Sista R, Eckhardt A, Rouse J, Bali D, Goldberg R, et al. Digital microfluidics: a future technology in the newborn screening laboratory? Semin Perinatol. 2010;34(2):163–9.PubMedCrossRefGoogle Scholar
  32. 32.
    Burton BK. Inborn errors of metabolism in infancy: a guide to diagnosis. Pediatrics. 1998;102(6):E69.PubMedCrossRefGoogle Scholar
  33. 33.
    American College of Medical Genetics and Genomics (ACMG). 2011. http://www.acmg.net/StaticContent/ACT/Algorithms/Visio-Phenylalanine.pdf. Accessed 6 July 2011.
  34. 34.
    National Institutes of Health (NIH) US. 2011. http://www.clinicaltrials.gov/ct2/results?term=Phenylketonuria+AND+phenylalanine+ammonia+lyase. Accessed 26 April 2012.
  35. 35.
    van Spronsen FJ, Enns GM. Future treatment strategies in phenylketonuria. Mol Genet Metab. 2010;99 Suppl 1:S90–5.PubMedCrossRefGoogle Scholar
  36. 36.
    Sarkissian CN, Gamez A, Scriver CR. What we know that could influence future treatment of phenylketonuria. J Inherit Metab Dis. 2009;32(1):3–9.PubMedCrossRefGoogle Scholar
  37. 37.
    Sarkissian CN, Gamez A. Phenylalanine ammonia lyase, enzyme substitution therapy for phenylketonuria, where are we now? Mol Genet Metab. 2005;86 Suppl 1:S22–6.PubMedCrossRefGoogle Scholar
  38. 38.
    Woolf LI, Griffiths R, Moncrieff A. Treatment of phenylketonuria with a diet low in phenylalanine. Br Med J. 1955;1(4905):57–64.PubMedCrossRefGoogle Scholar
  39. 39.
    Armstrong MD, Tyler FH. Studies on phenylketonuria. I. Restricted phenylalanine intake in phenylketonuria. J Clin Invest. 1955;34(4):565–80.PubMedCrossRefGoogle Scholar
  40. 40.
    Smith I, Wolff OH. Natural history of phenylketonuria and influence of early treatment. Lancet. 1974;2(7880):540–4.PubMedCrossRefGoogle Scholar
  41. 41.
    Mikoluc B, Witalis E, Jastrzebska-Piotrowska J, Wojcicka-Bartlomiejczyk B, Nowacka M, Starostecka E, et al. Diet compliance in patients with phenylketonuria (PKU)—influencing factors. J Inherit Metab Dis. 2006;29:51.Google Scholar
  42. 42.
    MacDonald A. Diet and compliance in phenylketonuria. Eur J Pediatr. 2000;159:S136–41.PubMedCrossRefGoogle Scholar
  43. 43.
    Walter JH, White FJ, Hall SK, MacDonald A, Rylance G, Boneh A, et al. How practical are recommendations for dietary control in phenylketonuria? Lancet. 2002;360(9326):55–7.PubMedCrossRefGoogle Scholar
  44. 44.
    Cotugno G, Nicolo R, Cappelletti S, Goffredo B, Dionisi Vici C, Di Ciommo V. Adherence to diet and quality of life in patients with phenylketonuria. Acta Paediatr. 2011;100(8):1144–9.PubMedCrossRefGoogle Scholar
  45. 45.
    Simon E, Schwarz M, Roos J, Dragano N, Geraedts M, Siegrist J, et al. Evaluation of quality of life and description of the sociodemographic state in adolescent and young adult patients with phenylketonuria (PKU). Health Qual Life Outcomes. 2008;6:25.PubMedCrossRefGoogle Scholar
  46. 46.
    Landolt MA, Nuoffer JM, Steinmann B, Superti-Furga A. Quality of life and psychologic adjustment in children and adolescents with early treated phenylketonuria can be normal. J Pediatr. 2002;140(5):516–21.PubMedCrossRefGoogle Scholar
  47. 47.
    ten Hoedt AE, de Sonneville LM, Francois B, ter Horst NM, Janssen MC, Rubio-Gozalbo ME, et al. High phenylalanine levels directly affect mood and sustained attention in adults with phenylketonuria: a randomised, double-blind, placebo-controlled, crossover trial. J Inherit Metab Dis. 2011;34(1):165–71.PubMedCrossRefGoogle Scholar
  48. 48.
    Mutze U, Roth A, Weigel JF, Beblo S, Baerwald CG, Buhrdel P, et al. Transition of young adults with phenylketonuria from pediatric to adult care. J Inherit Metab Dis. 2011;34(3):701–9.PubMedCrossRefGoogle Scholar
  49. 49.
    Smith I, Beasley MG, Ades AE. Intelligence and quality of dietary treatment in phenylketonuria. Arch Dis Child. 1990;65(5):472–8.PubMedCrossRefGoogle Scholar
  50. 50.
    Acosta PB, Yannicelli S, Singh T, Eisas LJ, Kennedy MJ, Bernstein L, et al. Intake and blood levels of fatty acids in treated patients with phenylketonuria. J Pediatr Gastr Nutr. 2001;33(3):253–9.CrossRefGoogle Scholar
  51. 51.
    Acosta PB, Yannicelli S, Singh R, Mofidi S, Steiner R, DeVincentis E, et al. Nutrient intakes and physical growth of children with phenylketonuria undergoing nutrition therapy. J Am Diet Assoc. 2003;103(9):1167–73.PubMedCrossRefGoogle Scholar
  52. 52.
    Acosta PB, Yannicelli S, Singh RH, Elsas LJ, Mofidi S, Steiner RD. Iron status of children with phenylketonuria undergoing nutrition therapy assessed by transferrin receptors. Genet Med. 2004;6(2):96–101.PubMedCrossRefGoogle Scholar
  53. 53.
    Schwahn B, Mokov E, Scheidhauer K, Lettgen B, Schonau E. Decreased trabecular bone mineral density in patients with phenylketonuria measured by peripheral quantitative computed tomography. Acta Paediatr. 1998;87(1):61–3.PubMedCrossRefGoogle Scholar
  54. 54.
    Cockburn F, Clark BJ, Caine EA, Harvie A, Farquharson J, Jamieson EC, et al. Fatty acids in the stability of neuronal membrane: relevance to PKU. Int Pediatr. 1996;11(1):56–60.Google Scholar
  55. 55.
    Koch R, Hanley W, Levy H, Matalon R, Rouse B, Trefz F, et al. Maternal phenylketonuria: an international study. Mol Genet Metab. 2000;71(1–2):233–9.PubMedCrossRefGoogle Scholar
  56. 56.
    Cockburn F, Clark BJ. Recommendations for protein and amino acid intake in phenylketonuric patients. Eur J Pediatr. 1996;155:S125–9.PubMedCrossRefGoogle Scholar
  57. 57.
    National Institutes of Health Consensus Development Panel. National Institutes of Health Consensus Development Conference Statement: phenylketonuria: screening and management, October 16–18, 2000. Pediatrics. 2001;108(4):972–82.Google Scholar
  58. 58.
    Werner ER, Blau N, Thony B. Tetrahydrobiopterin: biochemistry and pathophysiology. Biochem J. 2011;438(3):397–414.PubMedGoogle Scholar
  59. 59.
    Blaskovics MS, Schaeffl GE, Hack S. Phenylalaninaemia—differential diagnosis. Arch Dis Child. 1974;49(11):835–43.PubMedCrossRefGoogle Scholar
  60. 60.
    Longo N. Disorders of biopterin metabolism. J Inherit Metab Dis. 2009;32(3):333–42.PubMedCrossRefGoogle Scholar
  61. 61.
    Blau N, Thöny B, Cotton RGH, Hyland K. Disorders of tetrahydrobiopterin and related biogenic amines. In: Scriver CR, Beaudet AL, Sly WS, Valle D, Childs B, Vogelstein B, editors. The Metabolic and Molecular Bases of Inherited Disease. New York: McGraw-Hill; 2001. p. 1725–76.Google Scholar
  62. 62.
    Blau N, Thony B, Spada M, Ponzone A. Tetrahydrobiopterin and inherited hyperphenylalaninemias. Turkish J Pediatr. 1996;38(1):19–35.Google Scholar
  63. 63.
    Danks DM, Bartholome K, Clayton BE. Malignant hyperphenylalaninaemia. Current status (June 1977). J Inherit Metab Dis. 1978;1(2):49–53.PubMedCrossRefGoogle Scholar
  64. 64.
    Kure S, Hou DC, Ohura T, Iwamoto H, Suzuki S, Sugiyama N, et al. Tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency. J Pediatr. 1999;135(3):375–8.PubMedCrossRefGoogle Scholar
  65. 65.
    Muntau AC, Roschinger W, Habich M, Demmelmair H, Hoffmann B, Sommerhoff CP, et al. Tetrahydrobiopterin as an alternative treatment for mild phenylketonuria. New Engl J Med. 2002;347(26):2122–32.PubMedCrossRefGoogle Scholar
  66. 66.
    Blau N, Erlandsen H. The metabolic and molecular bases of tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency. Mol Genet Metab. 2004;82(2):101–11.PubMedCrossRefGoogle Scholar
  67. 67.
    Gersting SW, Kemter KF, Staudigl M, Messing DD, Danecka MK, Lagler FB, et al. Loss of function in phenylketonuria is caused by impaired molecular motions and conformational instability. Am J Hum Genet. 2008;83(1):5–17.PubMedCrossRefGoogle Scholar
  68. 68.
    Erlandsen H, Pey AL, Gamez A, Perez B, Desviat LR, Aguado C, et al. Correction of kinetic and stability defects by tetrahydrobiopterin in phenylketonuria patients with certain phenylalanine hydroxylase mutations. Proc Natl Acad Sci USA. 2004;101(48):16903–8.PubMedCrossRefGoogle Scholar
  69. 69.
    Kure S, Sato K, Fujii K, Aoki Y, Suzuki Y, Kato S, et al. Wild-type phenylalanine hydroxylase activity is enhanced by tetrahydrobiopterin supplementation in vivo: an implication for therapeutic basis of tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency. Mol Genet Metab. 2004;83(1–2):150–6.PubMedCrossRefGoogle Scholar
  70. 70.
    Muntau AC, Gersting SW. Phenylketonuria as a model for protein misfolding diseases and for the development of next generation orphan drugs for patients with inborn errors of metabolism. J Inherit Metab Dis. 2010;33(6):649–58.PubMedCrossRefGoogle Scholar
  71. 71.
    Aguado C, Perez B, Ugarte M, Desviat LR. Analysis of the effect of tetrahydrobiopterin on PAH gene expression in hepatoma cells. FEBS Lett. 2006;580(7):1697–701.PubMedCrossRefGoogle Scholar
  72. 72.
    Pey AL, Perez B, Desviat LR, Martinez MA, Aguado C, Erlandsen H, et al. Mechanisms underlying responsiveness to tetrahydrobiopterin in mild phenylketonuria mutations. Hum Mutat. 2004;24(5):388–99.PubMedCrossRefGoogle Scholar
  73. 73.
    Pey AL, Ying M, Cremades N, Velazquez-Campoy A, Scherer T, Thony B, et al. Identification of pharmacological chaperones as potential therapeutic agents to treat phenylketonuria. J Clin Invest. 2008;118(8):2858–67.PubMedCrossRefGoogle Scholar
  74. 74.
    Perez B, Desviat LR, Gomez-Puertas P, Martinez A, Stevens RC, Ugarte M. Kinetic and stability analysis of PKU mutations identified in BH4-responsive patients. Mol Genet Metab. 2005;86 Suppl 1:S11–6.PubMedCrossRefGoogle Scholar
  75. 75.
    Ames BN, Elson-Schwab I, Silver EA. High-dose vitamin therapy stimulates variant enzymes with decreased coenzyme binding affinity (increased K-m): relevance to genetic disease and polymorphisms. Am J Clin Nutr. 2002;75(4):616–58.PubMedGoogle Scholar
  76. 76.
    Hegge KA, Horning KK, Peitz GJ, Hegge K. Sapropterin: a new therapeutic agent for phenylketonuria. Ann Pharmacother. 2009;43(9):1466–73.PubMedCrossRefGoogle Scholar
  77. 77.
    Levy HL, Milanowski A, Chakrapani A, Cleary M, Lee P, Trefz FK, et al. 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(9586):504–10.PubMedCrossRefGoogle Scholar
  78. 78.
    Burton BK, Grange DK, Milanowski A, Vockley G, Feillet F, Crombez EA, et al. 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(5):700–7.PubMedCrossRefGoogle Scholar
  79. 79.
    Giugliani L, Sitta A, Vargas CR, Santana-da-Silva LC, Nalin T, Saraiva-Pereira ML, et al. Tetrahydrobiopterin responsiveness of patients with phenylalanine hydroxylase deficiency. J Pediatr (Rio J). 2011;87(3):245–51.CrossRefGoogle Scholar
  80. 80.
    Sanford M, Keating GM. Sapropterin a review of its use in the treatment of primary hyperphenylalaninaemia. Drugs. 2009;69(4):461–76.PubMedCrossRefGoogle Scholar
  81. 81.
    Burton BK, Nowacka M, Hennermann JB, Lipson M, Grange DK, Chakrapani A, et al. Safety of extended treatment with sapropterin dihydrochloride in patients with phenylketonuria: results of a phase 3b study. Mol Genet Metab. 2011;103(4):315–22.PubMedCrossRefGoogle Scholar
  82. 82.
    MacDonald A, Ahring K, Dokoupil K, Gokmen-Ozel H, Lammardo AM, Motzfeldt K, et al. Adjusting diet with sapropterin in phenylketonuria: what factors should be considered? Br J Nutr. 2011;106(2):175–82.PubMedCrossRefGoogle Scholar
  83. 83.
    Burton BK, Bausell H, Katz R, Laduca H, Sullivan C. Sapropterin therapy increases stability of blood phenylalanine levels in patients with BH4-responsive phenylketonuria (PKU). Mol Genet Metab. 2010;101(2–3):110–4.PubMedCrossRefGoogle Scholar
  84. 84.
    Burton BK, Adams DJ, Grange DK, Malone JI, Jurecki E, Bausell H, et al. Tetrahydrobiopterin therapy for phenylketonuria in infants and young children. J Pediatr. 2011;158(3):410–5.PubMedCrossRefGoogle Scholar
  85. 85.
    Trefz FK, Burton BK, Longo N, Casanova MM, Gruskin DJ, Dorenbaum A, et al. Efficacy of sapropterin dihydrochloride in increasing phenylalanine tolerance in children with phenylketonuria: a phase III, randomized, double-blind, placebo-controlled study. J Pediatr. 2009;154(5):700–7.PubMedCrossRefGoogle Scholar
  86. 86.
    Bik-Multanowski M, Pietrzyk JJ. Blood phenylalanine clearance and BH(4)-responsiveness in classic phenylketonuria. Mol Genet Metab. 2011;103(4):399–400.PubMedCrossRefGoogle Scholar
  87. 87.
    Fiege B, Ballhausen D, Kierat L, Leimbacher W, Goriounov D, Schircks B, et al. Plasma tetrahydrobiopterin and its pharmacokinetic following oral administration. Mol Genet Metab. 2004;81(1):45–51.PubMedCrossRefGoogle Scholar
  88. 88.
    Trefz FK, Belanger-Quintana A. Sapropterin dihydrochloride: a new drug and a new concept in the management of phenylketonuria. Drugs Today (Barc). 2010;46(8):589–600.CrossRefGoogle Scholar
  89. 89.
    Moller LB, Paulsen M, Koch R, Moats R, Guldberg P, Guttler F. Inter-individual variation in brain phenylalanine concentration in patients with PKU is not caused by genetic variation in the 4F2hc/LAT1 complex. Mol Genet Metab. 2005;86 Suppl 1:S119–23.PubMedCrossRefGoogle Scholar
  90. 90.
    Weglage J, Wiedermann D, Denecke J, Feldmann R, Koch HG, Ullrich K, et al. Individual blood–brain barrier phenylalanine transport determines clinical outcome in phenylketonuria. Ann Neurol. 2001;50(4):463–7.PubMedCrossRefGoogle Scholar
  91. 91.
    Koch R, Moats R, Guttler F, Guldberg P, Nelson Jr M. Blood–brain phenylalanine relationships in persons with phenylketonuria. Pediatrics. 2000;106(5):1093–6.PubMedCrossRefGoogle Scholar
  92. 92.
    Hawkins RA, O'Kane RL, Simpson IA, Vina JR. Structure of the blood–brain barrier and its role in the transport of amino acids. J Nutr. 2006;136(1 Suppl):218S–26S.PubMedGoogle Scholar
  93. 93.
    Christensen HN. Metabolism of amino acids and proteins. Annu Rev Biochem. 1953;22:233–60.PubMedCrossRefGoogle Scholar
  94. 94.
    Christensen HN, Streicher JA, Elbinger RL. Effects of feeding individual amino acids upon the distribution of other amino acids between cells and extracellular fluid. J Biol Chem. 1948;172(2):515–24.PubMedGoogle Scholar
  95. 95.
    Surtees R, Blau N. The neurochemistry of phenylketonuria. Eur J Pediatr. 2000;159 Suppl 2:S109–13.PubMedCrossRefGoogle Scholar
  96. 96.
    Andersen AE, Avins L. Lowering brain phenylalanine levels by giving other large neutral amino acids: a new experimental therapeutic approach to phenylketonuria. Arch Neurol. 1976;33(10):684–6.PubMedCrossRefGoogle Scholar
  97. 97.
    Pietz J, Kreis R, Rupp A, Mayatepek E, Rating D, Boesch C, et al. Large neutral amino acids block phenylalanine transport into brain tissue in patients with phenylketonuria. J Clin Invest. 1999;103(8):1169–78.PubMedCrossRefGoogle Scholar
  98. 98.
    Matalon R, Surendran S, Matalon KM, Tyring S, Quast M, Jinga W, et al. Future role of large neutral amino acids in transport of phenylalanine into the brain. Pediatrics. 2003;112(6):1570–4.PubMedGoogle Scholar
  99. 99.
    Matalon R, Michals-Matalon K, Bhatia G, Grechanina E, Novikov P, McDonald JD, et al. Large neutral amino acids in the treatment of phenylketonuria (PKU). J Inherit Metab Dis. 2006;29(6):732–8.PubMedCrossRefGoogle Scholar
  100. 100.
    Matalon R, Michals-Matalon K, Bhatia G, Burlina AB, Burlina AP, Braga C, et al. Double blind placebo control trial of large neutral amino acids in treatment of PKU: effect on blood phenylalanine. J Inherit Metab Dis. 2007;30(2):153–8.PubMedCrossRefGoogle Scholar
  101. 101.
    van Spronsen FJ, de Groot MJ, Hoeksma M, Reijngoud DJ, van Rijn M. Large neutral amino acids in the treatment of PKU: from theory to practice. J Inherit Metab Dis. 2010;33(6):671–6.PubMedCrossRefGoogle Scholar
  102. 102.
    Schindeler S, Ghosh-Jerath S, Thompson S, Rocca A, Joy P, Kemp A, et al. The effects of large neutral amino acid supplements in PKU: an MRS and neuropsychological study. Mol Genet Metab. 2007;91(1):48–54.PubMedCrossRefGoogle Scholar
  103. 103.
    Ney DM, Gleason ST, van Calcar SC, MacLeod EL, Nelson KL, Etzel MR, et al. Nutritional management of PKU with glycomacropeptide from cheese whey. J Inherit Metab Dis. 2009;32(1):32–9.PubMedCrossRefGoogle Scholar
  104. 104.
    Etzel MR. Manufacture and use of dairy protein fractions. J Nutr. 2004;134(4):996s–1002s.PubMedGoogle Scholar
  105. 105.
    Ney DM, MacLeod EL, Clayton MK, van Calcar SC. Breakfast with glycomacropeptide compared with amino acids suppresses plasma ghrelin levels in individuals with phenylketonuria. Mol Genet Metab. 2010;100(4):303–8.PubMedCrossRefGoogle Scholar
  106. 106.
    MacDonald A, Rylance G, Davies P, Asplin D, Hall SK, Booth IW. Administration of protein substitute and quality of control in phenylketonuria: a randomized study. J Inherit Metab Dis. 2003;26(4):319–26.PubMedCrossRefGoogle Scholar
  107. 107.
    Ney DM, van Calcar SC, MacLeod EL, Gleason ST, Etzel MR, Clayton MK, et al. Improved nutritional management of phenylketonuria by using a diet containing glycomacropeptide compared with amino acids. Am J Clin Nutr. 2009;89(4):1068–77.PubMedCrossRefGoogle Scholar
  108. 108.
    Vajro P, Strisciuglio P, Houssin D, Huault G, Laurent J, Alvarez F, et al. Correction of phenylketonuria after liver-transplantation in a child with cirrhosis. New Engl J Med. 1993;329(5):363.PubMedCrossRefGoogle Scholar
  109. 109.
    Ledley FD, Grenett HE, Dilella AG, Kwok SCM, Woo SLC. Gene-transfer and expression of human phenylalanine-hydroxylase. Science. 1985;228(4695):77–9.PubMedCrossRefGoogle Scholar
  110. 110.
    Liu TJ, Kay MA, Darlington GJ, Woo SL. Reconstitution of enzymatic activity in hepatocytes of phenylalanine hydroxylase-deficient mice. Somat Cell Mol Genet. 1992;18(1):89–96.PubMedCrossRefGoogle Scholar
  111. 111.
    Fang B, Eisensmith RC, Li XH, Finegold MJ, Shedlovsky A, Dove W, et al. Gene therapy for phenylketonuria: phenotypic correction in a genetically deficient mouse model by adenovirus-mediated hepatic gene transfer. Gene Ther. 1994;1(4):247–54.PubMedGoogle Scholar
  112. 112.
    Harding CO, Gillingham MB, Hamman K, Clark H, Goebel-Daghighi E, Bird A, et al. Complete correction of hyperphenylalaninemia following liver-directed, recombinant AAV2/8 vector-mediated gene therapy in murine phenylketonuria. Gene Ther. 2006;13(5):457–62.PubMedCrossRefGoogle Scholar
  113. 113.
    Laipis PJ, Charron CE, Embury JE, Perera OP, Porvasnik SL, Fields CR, et al. Correction of maternal phenylketonuria syndrome in the Pah(enu2) missense mutant mouse by r-AAV mediated gene therapy. Mol Ther. 2004;9:S334.Google Scholar
  114. 114.
    Mochizuki S, Mizukami H, Ogura T, Kure S, Ichinohe A, Kojima K, et al. Long-term correction of hyperphenylalaninemia by AAV-mediated gene transfer leads to behavioral recovery in phenylketonuria mice. Gene Ther. 2004;11(13):1081–6.PubMedCrossRefGoogle Scholar
  115. 115.
    Jacobs F, Wang L. Adeno-associated viral vectors for correction of inborn errors of metabolism: progressing towards clinical application. Curr Pharm Des. 2011;17(24):2500–15.PubMedCrossRefGoogle Scholar
  116. 116.
    Kay MA, Nakai H. Looking into the safety of AAV vectors. Nature. 2003;424(6946):251.PubMedCrossRefGoogle Scholar
  117. 117.
    Shedlovsky A, Mcdonald JD, Symula D, Dove WF. Mouse models of human phenylketonuria. Genetics. 1993;134(4):1205–10.PubMedGoogle Scholar
  118. 118.
    Cristiano RJ, Smith LC, Woo SL. Hepatic gene therapy: adenovirus enhancement of receptor-mediated gene delivery and expression in primary hepatocytes. Proc Natl Acad Sci USA. 1993;90(6):2122–6.PubMedCrossRefGoogle Scholar
  119. 119.
    Davidoff AM, Ng CYC, Zhou JF, Spence Y, Nathwani AC. Sex significantly influences transduction of murine liver by recombinant adeno-associated viral vectors through an androgen-dependent pathway. Blood. 2003;102(2):480–8.PubMedCrossRefGoogle Scholar
  120. 120.
    Ding Z, Georgiev P, Thony B. Administration-route and gender-independent long-term therapeutic correction of phenylketonuria (PKU) in a mouse model by recombinant adeno-associated virus 8 pseudotyped vector-mediated gene transfer. Gene Ther. 2006;13(7):587–93.PubMedCrossRefGoogle Scholar
  121. 121.
    Rebuffat A, Thony B, Harding CO, Ding ZB. Comparison of adeno-associated virus pseudotype 1, 2, and 8 vectors administered by intramuscular injection in the treatment of murine phenylketonuria. Hum Gene Ther. 2010;21(4):463–77.PubMedCrossRefGoogle Scholar
  122. 122.
    Yagi H, Kume A, Ogura T, Mizukami H, Urabe M, Hamada H, et al. Complete restoration of phenylalanine oxidation in phenylketonuria mouse by a self-complementary adeno-associated virus vector. J Gene Med. 2011;13(2):114–22.PubMedCrossRefGoogle Scholar
  123. 123.
    Harding CO, Wild K, Chang D, Messing A, Wolff JA. Metabolic engineering as therapy for inborn errors of metabolism—development of mice with phenylalanine hydroxylase expression in muscle. Gene Ther. 1998;5(5):677–83.PubMedCrossRefGoogle Scholar
  124. 124.
    Ding Z, Harding CO, Rebuffat A, Elzaouk L, Wolff JA, Thony B. Correction of murine PKU following AAV-mediated intramuscular expression of a complete phenylalanine hydroxylating system. Mol Ther. 2008;16(4):673–81.PubMedCrossRefGoogle Scholar
  125. 125.
    Gonzalez-Gonzalez E, Speaker TJ, Hickerson RP, Spitler R, Flores MA, Leake D, et al. Silencing of reporter gene expression in skin using siRNAs and expression of plasmid DNA delivered by a soluble protrusion array device (PAD). Mol Ther. 2010;18(9):1667–74.PubMedCrossRefGoogle Scholar
  126. 126.
    Pearton M, Allender C, Brain K, Anstey A, Gateley C, Wilke N, et al. Gene delivery to the epidermal cells of human skin explants using microfabricated microneedles and hydrogel formulations. Pharm Res. 2008;25(2):407–16.PubMedCrossRefGoogle Scholar
  127. 127.
    Jensen DM, Cun D, Maltesen MJ, Frokjaer S, Nielsen HM, Foged C. Spray drying of siRNA-containing PLGA nanoparticles intended for inhalation. J Control Release. 2010;142(1):138–45.PubMedCrossRefGoogle Scholar
  128. 128.
    Eavri R, Lorberboum-Galski H. A novel approach for enzyme replacement therapy. The use of phenylalanine hydroxylase-based fusion proteins for the treatment of phenylketonuria. J Biol Chem. 2007;282(32):23402–9.PubMedCrossRefGoogle Scholar
  129. 129.
    Pentchev PG, Brady RO, Gal AE, Hibbert SR. Replacement therapy for inherited enzyme deficiency—sustained clearance of accumulated glucocerebroside in gauchers-disease following infusion of purified glucocerebrosidase. J Mol Med. 1975;1(1):73–8.Google Scholar
  130. 130.
    Barton NW, Furbish FS, Murray GJ, Garfield M, Brady RO. Therapeutic response to intravenous infusions of glucocerebrosidase in a patient with Gaucher disease. Proc Natl Acad Sci USA. 1990;87(5):1913–6.PubMedCrossRefGoogle Scholar
  131. 131.
    Eng CM, Guffon N, Wilcox WR, Germain DP, Lee P, Waldek S, et al. Safety and efficacy of recombinant human alpha-galactosidase a replacement therapy in Fabry's disease. New Engl J Med. 2001;345(1):9–16.PubMedCrossRefGoogle Scholar
  132. 132.
    Coman DJ, Hayes IM, Collins V, Sahhar M, Wraith JE, Delatycki MB. Enzyme replacement therapy for mucopolysaccharidoses: opinions of patients and families. J Pediatr. 2008;152(5):723–7.PubMedCrossRefGoogle Scholar
  133. 133.
    Harmatz P, Whitley CB, Waber L, Pais R, Steiner R, Plecko B, et al. Enzyme replacement therapy in mucopolysaccharidosis VI (Maroteaux–Lamy syndrome). J Pediatr. 2004;144(5):574–80.PubMedCrossRefGoogle Scholar
  134. 134.
    Van den Hout JM, Kamphoven JH, Winkel LP, Arts WF, De Klerk JB, Loonen MC, et al. Long-term intravenous treatment of Pompe disease with recombinant human alpha-glucosidase from milk. Pediatrics. 2004;113(5):e448–57.PubMedCrossRefGoogle Scholar
  135. 135.
    Brady RO. Enzyme replacement for lysosomal diseases. Annu Rev Med. 2006;57:283–96.PubMedCrossRefGoogle Scholar
  136. 136.
    Harris JM, Chess RB. Effect of pegylation on pharmaceuticals. Nat Rev Drug Discov. 2003;2(3):214–21.PubMedCrossRefGoogle Scholar
  137. 137.
    Erlandsen H, Patch MG, Gamez A, Straub M, Stevens RC. Structural studies on phenylalanine hydroxylase and implications toward understanding and treating phenylketonuria. Pediatrics. 2003;112(6 Pt 2):1557–65.PubMedGoogle Scholar
  138. 138.
    Gamez A, Wang L, Straub M, Patch MG, Stevens RC. Toward PKU enzyme replacement therapy: PEGylation with activity retention for three forms of recombinant phenylalanine hydroxylase. Mol Ther. 2004;9(1):124–9.PubMedCrossRefGoogle Scholar
  139. 139.
    Bourget L, Chang TM. Phenylalanine ammonia-lyase immobilized in microcapsules for the depletion of phenylalanine in plasma in phenylketonuric rat model. Biochim Biophys Acta. 1986;883(3):432–8.PubMedCrossRefGoogle Scholar
  140. 140.
    Ambrus CM, Ambrus JL, Horvath C, Pedersen H, Sharma S, Kant C, et al. Phenylalanine depletion for management of phenylketonuria—use of enzyme reactors with immobilized enzymes. Science. 1978;201(4358):837–9.PubMedCrossRefGoogle Scholar
  141. 141.
    Kaufman S. Phenylketonuria and its variants. Adv Hum Genet. 1983;13:217–97.PubMedGoogle Scholar
  142. 142.
    Xiang LK, Moore BS. Biochemical characterization of a prokaryotic phenylalanine ammonia lyase. J Bacteriol. 2005;187(12):4286–9.PubMedCrossRefGoogle Scholar
  143. 143.
    Koukol J, Conn EE. Metabolism of aromatic compounds in higher plants. IV. Purification and properties of phenylalanine deaminase of Hordeum vulgare. J Biol Chem. 1961;236(10):2692–8.PubMedGoogle Scholar
  144. 144.
    Sikora LA, Marzluf GA. Regulation of l-phenylalanine ammonia-lyase by l-phenylalanine and nitrogen in Neurospora crassa. J Bacteriol. 1982;150(3):1287–91.PubMedGoogle Scholar
  145. 145.
    Hodgins DS. Yeast phenylalanine ammonia-lyase. Purification, properties, and the identification of catalytically essential dehydroalanine. J Biol Chem. 1971;246(9):2977–85.PubMedGoogle Scholar
  146. 146.
    Marusich WC, Jensen RA, Zamir LO. Induction of l-phenylalanine ammonia-lyase during utilization of phenylalanine as a carbon or nitrogen-source in Rhodotorula glutinis. J Bacteriol. 1981;146(3):1013–9.PubMedGoogle Scholar
  147. 147.
    Orndorff SA, Costantino N, Stewart D, Durham DR. Strain improvement of Rhodotorula graminis for production of a novel L-phenylalanine ammonia lyase. Appl Environ Microb. 1988;54(4):996–1002.Google Scholar
  148. 148.
    Fritz RR, Hodgins DS, Abell CW. Phenylalanine ammonia-lyase—induction and purification from yeast and clearance in mammals. J Biol Chem. 1976;251(15):4646–50.PubMedGoogle Scholar
  149. 149.
    Snapper I, Yu TF, Chiang YT. Cinnamic acid metabolism in man. P Soc Exp Biol Med. 1940;44:30–4.Google Scholar
  150. 150.
    Hoskins JA, Gray J. Phenylalanine ammonia-lyase in the management of phenylketonuria—the relationship between ingested cinnamate and urinary hippurate in humans. Res Commun Chem Path. 1982;35(2):275–82.Google Scholar
  151. 151.
    Shen RS, Fritz RR, Abell CW. Clearance of phenylalanine ammonia-lyase from normal and tumor-bearing mice. Cancer Res. 1977;37(4):1051–6.PubMedGoogle Scholar
  152. 152.
    Bourget L, Chang TMS. Phenylalanine ammonia-lyase immobilized in microcapsules for the depletion of phenylalanine in plasma in phenylketonuric rat model. Biochimica Et Biophysica Acta. 1986;883(3):432–8.PubMedCrossRefGoogle Scholar
  153. 153.
    Morishita M, Peppas NA. Is the oral route possible for peptide and protein drug delivery. Drug Discov Today. 2006;11(19–20):905–10.PubMedCrossRefGoogle Scholar
  154. 154.
    Hamman JH, Enslin GM, Kotze AF. Oral delivery of peptide drugs: barriers and developments. BioDrugs. 2005;19(3):165–77.PubMedCrossRefGoogle Scholar
  155. 155.
    Bourget L, Chang TM. Phenylalanine ammonia-lyase immobilized in semipermeable microcapsules for enzyme replacement in phenylketonuria. FEBS Lett. 1985;180(1):5–8.PubMedCrossRefGoogle Scholar
  156. 156.
    Habibi-Moini S, D'mello AP. Evaluation of possible reasons for the low phenylalanine ammonia lyase activity in cellulose nitrate membrane microcapsules. Int J Pharm. 2001;215(1–2):185–96.PubMedCrossRefGoogle Scholar
  157. 157.
    Shah RM, D'mello AP. Strategies to maximize the encapsulation efficiency of phenylalanine ammonia lyase in microcapsules. Int J Pharm. 2008;356(1–2):61–8.PubMedCrossRefGoogle Scholar
  158. 158.
    Figlewicz DA, Druse MJ. Experimental hyperphenylalaninemia: effect on central nervous system myelin subfractions. Exp Neurol. 1980;67(2):315–29.PubMedCrossRefGoogle Scholar
  159. 159.
    McDonald JD, Bode VC, Dove WF, Shedlovsky A. The use of N-ethyl-N-nitrosourea to produce mouse models for human phenylketonuria and hyperphenylalaninemia. Prog Clin Biol Res. 1990;340 C:407–13.Google Scholar
  160. 160.
    Safos S, Chang TM. Enzyme replacement therapy in ENU2 phenylketonuric mice using oral microencapsulated phenylalanine ammonia-lyase: a preliminary report. Artif Cells Blood Substit Immobil Biotechnol. 1995;23(6):681–92.PubMedCrossRefGoogle Scholar
  161. 161.
    Evans CT, Hanna K, Conrad D, Peterson W, Misawa M. Production of phenylalanine ammonia-lyase (PAL)—isolation and evaluation of yeast strains suitable for commercial production of l-phenylalanine. Appl Microbiol Biot. 1987;25(5):406–14.Google Scholar
  162. 162.
    Orum H, Rasmussen OF. Expression in Escherichia coli of the gene encoding phenylalanine ammonia-lyase from Rhodosporidium toruloides. Appl Microbiol Biot. 1992;36(6):745–8.CrossRefGoogle Scholar
  163. 163.
    Sarkissian CN, Shao Z, Blain F, Peevers R, Su H, Heft R, et al. A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase. Proc Natl Acad Sci USA. 1999;96(5):2339–44.PubMedCrossRefGoogle Scholar
  164. 164.
    Sarkissian CN, Boulais DM, McDonald JD, Scriver CR. A heteroallelic mutant mouse model: a new orthologue for human hyperphenylalaninemia. Mol Genet Metab. 2000;69(3):188–94.PubMedCrossRefGoogle Scholar
  165. 165.
    Wang L, Gamez A, Sarkissian CN, Straub M, Patch MG, Won Han G, et al. Structure-based chemical modification strategy for enzyme replacement treatment of phenylketonuria. Mol Genet Metab. 2005;86(1–2):134–40.PubMedCrossRefGoogle Scholar
  166. 166.
    Gamez A, Sarkissian CN, Wang L, Kim W, Straub M, Patch MG, et al. Development of pegylated forms of recombinant Rhodosporidium toruloides phenylalanine ammonia-lyase for the treatment of classical phenylketonuria. Mol Ther. 2005;11(6):986–9.PubMedCrossRefGoogle Scholar
  167. 167.
    Ikeda K, Schiltz E, Fujii T, Takahashi M, Mitsui K, Kodera Y, et al. Phenylalanine ammonia-lyase modified with polyethylene glycol: potential therapeutic agent for phenylketonuria. Amino Acids. 2005;29(3):283–7.PubMedCrossRefGoogle Scholar
  168. 168.
    Moffitt MC, Louie GV, Bowman ME, Pence J, Noel JP, Moore BS. Discovery of two cyanobacterial phenylalanine ammonia lyases: kinetic and structural characterization. Biochemistry. 2007;46(4):1004–12.PubMedCrossRefGoogle Scholar
  169. 169.
    Wang L, Gamez A, Archer H, Abola EE, Sarkissian CN, Fitzpatrick P, et al. Structural and biochemical characterization of the therapeutic Anabaena variabilis phenylalanine ammonia lyase. J Mol Biol. 2008;380(4):623–35.PubMedCrossRefGoogle Scholar
  170. 170.
    Sarkissian CN, Gamez A, Wang L, Charbonneau M, Fitzpatrick P, Lemontt JF, et al. Preclinical evaluation of multiple species of PEGylated recombinant phenylalanine ammonia lyase for the treatment of phenylketonuria. Proc Natl Acad Sci USA. 2008;105(52):20894–9.PubMedCrossRefGoogle Scholar
  171. 171.
    Kang TS, Wang L, Sarkissian CN, Gamez A, Scriver CR, Stevens RC. Converting an injectable protein therapeutic into an oral form: phenylalanine ammonia lyase for phenylketonuria. Mol Genet Metab. 2010;99(1):4–9.PubMedCrossRefGoogle Scholar
  172. 172.
    Sarkissian CN, Kang TS, Gamez A, Scriver CR, Stevens RC. Evaluation of orally administered PEGylated phenylalanine ammonia lyase in mice for the treatment of phenylketonuria. Mol Genet Metab. 2011;104(3):249–54.PubMedCrossRefGoogle Scholar
  173. 173.
    Liu J, Jia X, Zhang J, Xiang H, Hu W, Zhou Y. Study on a novel strategy to treatment of phenylketonuria. Artif Cells Blood Substit Immobil Biotechnol. 2002;30(4):243–57.PubMedCrossRefGoogle Scholar
  174. 174.
    Zhang YL, Wang LY, Jia XY, Liu JZ, Ma GH. Preparation of Ca-alginate microparticles and its application for phenylketonuria oral therapy. Ind Eng Chem Res. 2011;50(7):4106–12.CrossRefGoogle Scholar
  175. 175.
    Dubey S, Kalia YN. Electrically-assisted delivery of an anionic protein across intact skin: cathodal iontophoresis of biologically active ribonuclease T1. J Control Release. 2011;152(3):356–62.PubMedCrossRefGoogle Scholar
  176. 176.
    Kim Y-C, Prausnitz M. Enabling skin vaccination using new delivery technologies. Drug Deliv Transl Res. 2011;1(1):7–12.PubMedCrossRefGoogle Scholar
  177. 177.
    Depreter F, Amighi K. Formulation and in vitro evaluation of highly dispersive insulin dry powder formulations for lung administration. Eur J Pharm Biopharm. 2010;76(3):454–63.PubMedCrossRefGoogle Scholar
  178. 178.
    Mudaliar S. Inhaled insulin using AERx insulin diabetes management system (AERx iDMS). Expert Opin Invest Drugs. 2007;16(10):1673–81.CrossRefGoogle Scholar

Copyright information

© Controlled Release Society 2012

Authors and Affiliations

  • Jaspreet Singh Kochhar
    • 1
  • Sui Yung Chan
    • 1
  • Pei Shi Ong
    • 1
  • Lifeng Kang
    • 1
  1. 1.Department of PharmacyNational University of SingaporeSingaporeSingapore

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