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01.12.2017 | Research | Ausgabe 1/2017 Open Access

Orphanet Journal of Rare Diseases 1/2017

Efficacy, safety and population pharmacokinetics of sapropterin in PKU patients <4 years: results from the SPARK open-label, multicentre, randomized phase IIIb trial

Orphanet Journal of Rare Diseases > Ausgabe 1/2017
Ania C. Muntau, Alberto Burlina, François Eyskens, Peter Freisinger, Corinne De Laet, Vincenzo Leuzzi, Frank Rutsch, H. Serap Sivri, Suresh Vijay, Milva Orquidea Bal, Gwendolyn Gramer, Renata Pazdírková, Maureen Cleary, Amelie S. Lotz-Havla, Alain Munafo, Diane R. Mould, Flavie Moreau-Stucker, Daniela Rogoff
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The online version of this article (doi:10.​1186/​s13023-017-0600-x) contains supplementary material, which is available to authorized users.



Sapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC, was initially approved in Europe only for patients ≥4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children <4 years.


In total, 109 male or female children <4 years with confirmed BH4-responsive phenylketonuria or mild hyperphenylalaninemia and good adherence to dietary treatment were screened. 56 patients were randomly assigned (1:1) to 10 mg/kg/day oral sapropterin plus a phenylalanine-restricted diet or to only a phenylalanine-restricted diet for 26 weeks (27 to the sapropterin and diet group and 29 to the diet-only group; intention-to-treat population). Of these, 52 patients with ≥1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7–42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using non-linear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters.


The addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children <4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients <4 years with BH4-responsive phenylketonuria.

Trial registration, NCT01376908. Registered June 17, 2011.
Additional file 1: Figure S1. Summary of neuromotor developmental milestones – ITT population. Data show (a) the proportion of patients with normal development in the area of assessment at baseline, (b) Week 12, and (c) Week 26 treated with sapropterin plus the Phe-restricted diet, or Phe-restricted diet alone. P-values show comparison of results between treatment groups at Week 26 using the chi-squared test. Table S1. PAH genotypes of sapropterin responders (n=37). (DOCX 180 kb)
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