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Merck Announces Detailed 26-Week Results from Phase IIIb Study with Kuvan in Children with PKU Below 4 Years of Age

DARMSTADT, Germany, September 3, 2014 /PRNewswire/ --

Not intended for UK based media


  • Detailed 26-week results of SPARK study presented at SSIEM Annual Symposium 
  • Phenylalanine tolerance significantly increased in children with PKU below 4 years of age, previously shown to be responsive to Kuvan and treated with Kuvan plus a phenylalanine-restricted diet, versus diet alone (p<0.001) 

Merck Serono, the biopharmaceutical division of Merck, announced today that detailed 26-week data from the Phase IIIb SPARK study are being presented at the Society for the Study of Inborn Errors of Metabolism (SSIEM) Annual Symposium, currently taking place in Innsbruck, Austria. As announced in April, the study met its primary endpoint. It showed that the addition of Kuvan® (sapropterin dihydrochloride) at a dose of 10 or 20 mg/kg/day to a phenylalanine-restricted diet significantly increased phenylalanine tolerance by 30.5 mg/kg/day in children with phenylketonuria (PKU) who are below 4 years of age and responsive to Kuvan compared with that of patients on diet alone (p<0.001).

The group of patients receiving Kuvan had an adjusted mean phenylalanine tolerance of 80.6 mg/kg/day at the end of 26 weeks of treatment compared with that of 50.1 mg/kg/day in the group of patients receiving diet alone (∆ 30.5 mg/kg/day). The mean phenylalanine tolerance in the group receiving Kuvan in addition to a phenylalanine-restricted diet (n=27) increased from a baseline of 37.1 mg/kg/day (standard deviation [SD] 17.3 mg/kg/day) to 80.6 mg/kg/day (SD 4.2 mg/kg/day) after 26 weeks. In the group following a phenylalanine-restricted diet alone (n=29), the increase was from 35.8 mg/kg/day (SD 20.9 mg/kg/day) to 50.1 mg/kg/day (SD 4.3 mg/kg/day).

The safety profile of Kuvan in this population was consistent with the safety profile of Kuvan described in the European Summary of Product Characteristics, which lists the most common adverse reactions reported with the use of Kuvan, including headache, runny nose, diarrhea, vomiting, sore throat, cough, abdominal pain, stuffy nose and low levels of phenylalanine in the blood. The most frequent Kuvan-related adverse reactions in the SPARK trial were reported as "amino acid level decreased" (hypophenylalaninemia), rhinitis and vomiting. SPARK was requested by the European Medicines Agency (EMA) as a post-authorization measure and demonstrates Merck's commitment to addressing areas of high unmet medical need. The positive outcome of the trial will enable the submission of an application for a label extension this year, and study results will be submitted for publication in a peer-reviewed journal.

"This study was designed to investigate if children below 4 years of age with PKU could potentially benefit from adding Kuvan to their phenylalanine-restricted diet," said Professor Ania Muntau, previously Dr. von Hauner Children's Hospital Ludwig-Maximilians University, Munich, Germany, and now University Medical Center Hamburg-Eppendorf, Hamburg, Germany, and lead investigator for SPARK. "It is the first time a controlled study such as this has been conducted in this population and the study results have the potential to significantly change treatment strategies with immediate start of a pharmacological treatment in newborns diagnosed to have phenylketonuria responsive to sapropterin dihydrochloride."

PKU is an inborn metabolic disorder that causes the toxic accumulation of phenylalanine, an essential amino acid found in all protein-containing foods, in the brain and blood.[1],[2] Untreated, PKU can lead to intellectual disability, seizures and other serious medical problems.[1],[2] In many countries, implementation of national newborn screening programs has allowed identification of children with PKU at birth, enabling the management of the disease to begin as early as possible in order to prevent potentially severe neurological damage.[3]

Luciano Rossetti, Head of Global Research & Development at Merck Serono underlined the company's commitment to better management of PKU for all those affected by it: "Although rare, we know that PKU can have profound and far-reaching consequences if not managed appropriately right from birth. These results add to the growing insights for the medical community around PKU in infants and young children."

SPARK is a Phase IIIb, multicenter, open-label, randomized, controlled study designed to assess the efficacy, safety, and population pharmacokinetics of Kuvan in patients younger than 4 years old with PKU who have been previously shown to be responsive to Kuvan in a response test. The study was conducted under a Pediatric Investigational Plan. Patients were randomized to Kuvan (10 mg/kg/day) plus a phenylalanine-restricted diet, or to a phenylalanine-restricted diet alone, for 26 weeks. Subject to a patient's phenylalanine tolerance after approximately 4 weeks, the Kuvan dose could be increased in a single step to 20 mg/kg/day. The primary endpoint of the study was to compare phenylalanine tolerance achieved in both arms after 26 weeks of treatment. Secondary study endpoints included change in levels of blood phenylalanine during the study period, change in dietary phenylalanine tolerance over time (from baseline to 26 weeks) in both groups, as well as assessment of neurodevelopmental function, growth parameters and safety. The long-term efficacy and safety of Kuvan are being assessed in the ongoing study's 3-year extension period, in which all patients are offered to receive Kuvan in addition to the phenylalanine-restricted diet.

The Kuvan European marketing authorization was granted in 2008. Kuvan was the first, and remains the only, medication in combination with dietary modifications in Europe designed to reduce the concentration of phenylalanine in the blood and in the brain in those patients who are responsive to Kuvan to prevent the debilitating effects of PKU.[4] Kuvan is indicated in patients of all ages with tetrahydrobiopterin (BH4) deficiency, and in those aged 4 years and above with PKU (due to phenylalanine hydroxylase enzyme deficiency) who are responsive to Kuvan. Currently, there is no licensed medication in Europe for the treatment of PKU in children who are below 4 years of age. Kuvan is marketed by Merck Serono outside the USA, Canada and Japan, by BioMarin in the USA and Canada, and under the name Biopten® by Asubio Pharma in Japan. In the USA and Europe, Kuvan received orphan drug designation.

*SPARK: Safety Pediatric EfficAcy PhaRmacokinetic with Kuvan (sapropterin dihydrochloride)


  1. Blau N: Phenylketonuria and BH4 deficiencies. Bremen: Uni-Med; 2010
  2. Blau N, van Spronsen FJ, Levy HL: Phenylketonuria. Lancet 2010,376:1417-1427
  3. Loeber JG. Neonatal screening in Europe: the situation in 2004. J Inherit Metab Dis 2007;30:30-38
  4., Accessed 31.03.2014

About phenylketonuria (PKU) 

PKU is an autosomal recessive genetic disorder caused by a defect or a deficiency of the enzyme phenylalanine hydroxylase (PAH). PAH is required for the metabolism of phenylalanine, an essential amino acid found in all protein-containing foods. It affects approximately 1/10,000 newborns in Europe. If PKU patients are not treated with a phenylalanine-restricted diet, phenylalanine will accumulate in the blood and brain to abnormally high levels, thereby resulting in a variety of complications including clinically significant mental retardation and brain damage, mental illness, seizures and tremors, and cognitive problems. Universal systematic newborn screening programs were developed in the 1960s and early 1970s to enable diagnosis of all patients with PKU patients at birth.

About tetrahydrobiopterin (BH4) deficiency 

BH4 deficiency is a very rare inborn error of metabolism, and is estimated to account for 1-2 % of cases of hyperphenylalaninemia (HPA). BH4 deficiency is an autosomal recessive genetic condition and can result from deficiencies of any of the five different enzymes involved in BH4 synthesis and regeneration. BH4 is a necessary co-factor for PAH. Therefore, BH4 deficiency impairs PAH activity leading to a biochemical situation similar to PKU, with HPA resulting from deficient conversion of phenylalanine to tyrosine. In addition, since BH4 is also a necessary co-factor for both tyrosine hydroxylase and tryptophan hydroxylase, BH4 deficiency causes deficiencies in the downstream neurotransmitter products of these amino acids including catecholamines and serotonin. Dietary limitation of whole protein or phenylalanine intake is often not necessary with BH4 treatment. However, since BH4 does not cross the blood brain barrier, concomitant therapy with neurotransmitter precursors, i.e. levodopa and 5-hydroxytryptophan, may be necessary to boost central nervous system substrate levels for catecholamine and serotonin synthesis, respectively.

About Kuvan 

Kuvan® (sapropterin dihydrochloride) is an oral therapy and the first treatment indicated in Europe in conjunction with a phenylalanine-restricted diet, for the treatment of hyperphenylalaninemia (HPA) due to phenylketonuria (PKU) in patients from the age of 4 who have shown to be responsive to Kuvan, or due to tetrahydrobiopterin (BH4) deficiency. Kuvan was developed jointly by BioMarin Pharmaceutical Inc. and Merck Serono. In the US, Kuvan is marketed by BioMarin and is indicated for the treatment of HPA due to PKU without age restriction. The current label states that safety and efficacy of Kuvan in pediatric patients less than 4 years of age have not been established in clinical studies. Kuvan is to be used in conjunction with a phenylalanine-restricted diet.

Kuvan is the synthetic form of 6R-BH4, a naturally occurring co-factor that works in conjunction with the enzyme phenylalanine hydroxylase (PAH) to metabolize phenylalanine into tyrosine. Clinical data show that Kuvan produces significant reductions in blood phenylalanine concentration in a large subset of patients.

Most common adverse reactions reported with the use of Kuvan include headache, runny nose, diarrhea, vomiting, sore throat, cough, abdominal pain, stuffy nose and low levels of phenylalanine in the blood.

Kuvan is approved in 49 countries worldwide, including member states of the European Union and the USA. Under the terms of the agreement with BioMarin, Merck Serono has exclusive rights to market Kuvan in all territories outside the USA, Canada and Japan.

About Merck Serono 

Merck Serono is the biopharmaceutical division of Merck. With headquarters in Darmstadt, Germany, Merck Serono offers leading brands in 150 countries to help patients with cancer, multiple sclerosis, infertility, endocrine and metabolic disorders as well as cardiovascular diseases. In the United States and Canada, EMD Serono operates as a separately incorporated subsidiary of Merck Serono.

Merck Serono discovers, develops, manufactures and markets prescription medicines of both chemical and biological origin in specialist indications. We have an enduring commitment to deliver novel therapies in our core focus areas of neurology, oncology, immuno-oncology and immunology.

For more information, please visit

All Merck Press Releases are distributed by e-mail at the same time they become available on the Merck Website. Please go to to register online, change your selection or discontinue this service.

Merck is a leading company for innovative and top-quality high-tech products in the pharmaceutical and chemical sectors. With its four divisions Merck Serono, Consumer Health, Performance Materials and Merck Millipore, Merck generated total revenues of € 11.1 billion in 2013. Around 39,000 Merck employees work in 66 countries to improve the quality of life for patients, to further the success of customers and to help meet global challenges. Merck is the world's oldest pharmaceutical and chemical company - since 1668, the company has stood for innovation, business success and responsible entrepreneurship. Holding an approximately 70 percent interest, the founding family remains the majority owner of the company to this day. Merck, Darmstadt, Germany is holding the global rights to the Merck name and brand. The only exceptions are Canada and the United States, where the company is known as EMD.

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