Phase 2 Study of Glycomacropeptide Versus Amino Acid Diet for Management of Phenylketonuria (PKU)

• ClinicalTrials.gov Identifier: NCT01428258
• Recruitment Status: Completed
• First Posted: September 2, 2011
• Results First Posted: March 3, 2017
• Last Update Posted: August 24, 2018
• Sponsor: University of Wisconsin, Madison
• Collaborator: Boston Children's Hospital
• Information provided by (Responsible Party): University of Wisconsin, Madison

Study Description

Brief Summary:

For individuals with Phenylketonuria (PKU), the investigators hypothesize that glycomacropeptide will provide an acceptable form of low-phenylalanine dietary protein that will improve dietary compliance, blood phenylalanine levels, cognitive function, and ultimately quality of life compared with the usual amino acid based diet. The study is funded by the Food and Drug Administration (FDA) Office of Orphan Products Development Grants Program, R01 FD003711.

Condition or disease	Intervention/treatment	Phase
Phenylketonuria	Other: GMP Diet/GMP Medical Foods; Other: AA Diet/AA Medical Foods	Not Applicable

Detailed Description:

Individuals with phenylketonuria (PKU) lack the enzyme phenylalanine hydroxylase that is needed to metabolize the essential amino acid phenylalanine (phe). When eating a normal diet they show an elevated level of phe in blood that is toxic to the brain. In order to prevent brain damage and cognitive impairment, individuals with PKU must follow a lifelong, low-phe diet that is restricted in natural foods and requires ingestion of a phe-free amino acid (AA) formula. Most adolescents and adults with PKU find the AA formula unpalatable and go off the diet resulting in elevated blood phe levels and neuropsychological deterioration. Glycomacropeptide (GMP), an intact protein produced during cheese making, is uniquely suited to a low-phe diet because it is the only known dietary protein that contains minimal phe. Foods and beverages made with GMP are a palatable alternative to AA formula. The long term goal is to assess the safety, efficacy and acceptability of GMP for the nutritional management of PKU. The specific aim is to conduct a randomized, two-stage, 11-wk, crossover trial comparing the GMP diet with the AA diet in 30 subjects with PKU ≥12 years of age treated since birth with a low-phe AA diet. The sites are: University of Wisconsin-Madison, Waisman Center (primary) and Harvard University, Children's Hospital Boston. Subjects will be recruited and randomized to begin the first 3-wk of the study with either a low-phe diet in which the majority of dietary protein is provided by GMP or AA medical foods and then, after a 3-wk washout with intake of their usual diet, begin the second diet for 3-wk. Dietary education will be provided in a 1-wk base period preceding initiation of each diet.

Study Design

• Study Type: Interventional (Clinical Trial)
• Actual Enrollment: 32 participants
• Allocation: Randomized
• Intervention Model: Crossover Assignment
• Intervention Model Description: The study is a randomized, two-arm, crossover trial comparing the GMP diet and the AA diet in 30 subjects with PKU > 12 years of age. Subjects were randomized to start with either the GMP diet or the AA diet which they followed for 3-wk at home, followed by a 3-wk washout period when they resumed their usual AA diet, and then 3-wk of either the GMP diet or the AA diet whichever they did not consume first. Each subject served as their own control; there was no control group. We studied medical foods - either AA or GMP medical foods which are not drugs. The FDA did not require that we have an IND.
• Masking: None (Open Label)
• Primary Purpose: Treatment
• Official Title: Phase 2 Study of Glycomacropeptide vs. Amino Acid Diet for the Management of PKU
• Study Start Date: September 2011
• Actual Primary Completion Date: November 2015
• Actual Study Completion Date: May 2016

Arms and Interventions

Arm	Intervention/treatment
Experimental: GMP Diet/GMP Medical Foods; The experimental intervention is the GMP diet followed at home for 3-wk. In this randomized crossover study, half of subjects (n=15) were randomized to receive the GMP diet as the first arm, and half of the subjects (n=15) were randomized to receive the GMP diet as the second arm.	Other: AA Diet/AA Medical Foods; The intervention consists of a low-Phe diet in combination with commercial AA medical foods as consumed in each subject's usual diet. A total of 15 different commercial AA medical foods were consumed by subjects in the study. The diet is formulated to provide each subject with their typical daily intake of protein equivalents from AA medical foods. The AA dietary treatment period consists of all subjects following the AA diet for 3-wks at home. The AA Diet comparator intervention is administered in differing orders, GMP Diet/AA Diet or AA diet/GMP Diet.; Other Name: AA Medical Foods
Active Comparator: AA Diet/AA Medical Foods; The experimental intervention is the AA diet followed at home for 3-wk. In this randomized crossover study, half of subjects (n=15) were randomized to receive the AA diet as the first arm, and half of the subjects (n=15) were randomized to receive the AA diet as the second arm.	Other: GMP Diet/GMP Medical Foods; The intervention consists of a low-phenylalanine (Phe) diet in combination with medical foods made with the peptide GMP supplemented with limiting indispensable amino acids, as provided by Cambrooke Therapeutics, LLC. The diet is formulated to replace the protein equivalents provided by AA medical foods with GMP medical foods, keeping other dietary components constant. The GMP dietary treatment period consists of all subjects following the GMP diet for 3-wks at home. The GMP diet intervention is administered in differing orders, GMP Diet/AA Diet or AA diet/GMP Diet.; Other Names: GMP Medical Foods; Glytactin trademark of Cambrooke Therapeutics,LLC

Outcome Measures

Primary Outcome Measures :

1. Change in the Plasma Phenylalanine Concentration of PKU Subjects Fed the Glycomacropeptide Diet Compared With the Change When Fed the Amino Acid Diet [ Time Frame: baseline to day 22 on each diet ]
   Plasma will be collected at each base week and after 3 weeks on each of the dietary treatments, glycomacropeptide and amino acid, following an overnight fast. Plasma phenylalanine concentration (along with the complete profile of free amino acids) will be determined with an amino acid analyzer in the Wisconsin State Lab of Hygiene. Statistical analysis to determine the significance of the change in plasma phe concentration when comparing the 2 diets will consist of ANCOVA with covariates for baseline Phe and dietary Phe intake. The change in plasma Phe concentration from day 22 (final) to day 1 (baseline) was determined after adjusting for baseline Phe level and dietary Phe intake.

Secondary Outcome Measures :

1. Dietary Compliance [ Time Frame: 3 week dietary treatment ]
   Compliance with the glycomacropeptide and amino acid dietary treatments will be assessed by comparison of the intake of medical food in grams of protein from medical food per day based on subject completion of 3-day food records prior to the final study visit on day 22. Statistical analysis for a dietary treatment effect will consist of ANOVA.
2. Executive Function Assessed by BRIEF [ Time Frame: day 22 of each dietary treatment ]
   Completion of a standardized test, the Behavior Rating Inventory of Executive Function (BRIEF), by each subject for the GMP diet and the AA diet. Values are T-scores which have a mean of 50 points and a SD of 10 points. A T score of <50 is considered within the normative range. Data are analyzed with a paired t-test.
3. Vitamin D (25-OH) Plasma Concentration at Day 22 [ Time Frame: day 22 of each dietary treatment ]
   Vitamin D was measured as a measure of the capacity for calcium absorption. Higher levels of plasma vitamin D are consistent with higher calcium absorption.
4. Comparison of Phe Concentrations in Plasma With Concentrations in Dried Blood Spots [ Time Frame: 4 times total, 2 per treatment ]
   Concentrations of Phe in plasma and in dried blood spots collected simultaneously by subjects will be compared using 2 methodologies, regardless of intervention. At each of the 4 study visits (baseline and final for each dietary treatment): 1) venipuncture was used to collect blood and plasma was isolated and analyzed for Phe with ion exchange chromatography and 2) subjects were asked right after the venipuncture to spot their blood on filter paper for analysis of Phe with tandem mass spectroscopy (MS/MS). The discrepancy in Phe concentrations with these 2 methods was compared for each sample pair using Bland-Altman statistical analysis. Each subject should have had 4 sample pairs, 29 x 4 = 116, but we ended up with only 110 sample pairs, as explained below.
5. Bone-specific Alkaline Phosphatase (BSAP) Plasma Concentration at Day 22 [ Time Frame: day 22 of each dietary treatment ]
   Plasma concentration of BSAP was determined as a measure of bone turnover.
6. N-terminal Telopeptide (NTX) Plasma Concentration at Day 22 [ Time Frame: day 22 of each dietary treatment ]
   Plasma concentration of NTX was determined as a measure of bone resorption; higher levels indicate greater bone breakdown

Other Outcome Measures:

1. Bone Mineral Density Determined by Dual-energy X-ray Absorptiometry (DXA) Scan [ Time Frame: once during first 3 week dietary treatment ]
   Subjects will have a single DXA test to assess bone mineral density of the lumbar spine and total body during the first dietary treatment that they are randomly assigned to start with.

Eligibility Criteria

• Ages Eligible for Study: 12 Years to 45 Years (Child, Adult)
• Sexes Eligible for Study: All
• Accepts Healthy Volunteers: No

Criteria

Inclusion Criteria:

• Identified PKU by newborn screening; started diet treatment before 1 mo age
• Diagnosis of classical or variant PKU with documented phenylalanine level of greater than 600 umol/L at 7-10d of age
• Follows or willing to follow PKU diet and consume amino acid medical formula providing more than 50% of protein needs
• Acceptance of glycomacropeptide foods determined prior to enrollment

Exclusion Criteria:

• Females who are pregnant or planning pregnancy
• Individuals with mental deficits due to untreated or poorly controlled PKU
• Individuals with any health condition deemed to interfere with participation

Contacts and Locations

Locations

United States, Massachusetts

Children's Hospital of Boston

Boston, Massachusetts, United States, 02115

United States, Wisconsin

University of Wisconsin-Madison

Madison, Wisconsin, United States, 53706

Sponsors and Collaborators

University of Wisconsin, Madison

Boston Children's Hospital

Investigators

• Study Director: Denise M Ney, PhD, RD; Professor of Nutritional Sciences, University of Wisconsin-Madison

More Information

Additional Information:

National PKU Alliance 

Publications of Results:

Ney DM, Stroup BM, Clayton MK, Murali SG, Rice GM, Rohr F, Levy HL. Glycomacropeptide for nutritional management of phenylketonuria: a randomized, controlled, crossover trial. Am J Clin Nutr. 2016 Aug;104(2):334-45. doi: 10.3945/ajcn.116.135293. Epub 2016 Jul 13.

Stroup BM, Held PK, Williams P, Clayton MK, Murali SG, Rice GM, Ney DM. Clinical relevance of the discrepancy in phenylalanine concentrations analyzed using tandem mass spectrometry compared with ion-exchange chromatography in phenylketonuria. Mol Genet Metab Rep. 2016 Jan 16;6:21-6. doi: 10.1016/j.ymgmr.2016.01.001. eCollection 2016 Mar.

Ney DM, Murali SG, Stroup BM, Nair N, Sawin EA, Rohr F, Levy HL. Metabolomic changes demonstrate reduced bioavailability of tyrosine and altered metabolism of tryptophan via the kynurenine pathway with ingestion of medical foods in phenylketonuria. Mol Genet Metab. 2017 Jun;121(2):96-103. doi: 10.1016/j.ymgme.2017.04.003. Epub 2017 Apr 6.

Stroup BM, Murali SG, Nair N, Sawin EA, Rohr F, Levy HL, Ney DM. Dietary amino acid intakes associated with a low-phenylalanine diet combined with amino acid medical foods and glycomacropeptide medical foods and neuropsychological outcomes in subjects with phenylketonuria. Data Brief. 2017 Jun 7;13:377-384. doi: 10.1016/j.dib.2017.06.004. eCollection 2017 Aug.

Stroup BM, Sawin EA, Murali SG, Binkley N, Hansen KE, Ney DM. Amino Acid Medical Foods Provide a High Dietary Acid Load and Increase Urinary Excretion of Renal Net Acid, Calcium, and Magnesium Compared with Glycomacropeptide Medical Foods in Phenylketonuria. J Nutr Metab. 2017;2017:1909101. doi: 10.1155/2017/1909101. Epub 2017 May 4.

Stroup BM, Ney DM, Murali SG, Rohr F, Gleason ST, van Calcar SC, Levy HL. Metabolomic Insights into the Nutritional Status of Adults and Adolescents with Phenylketonuria Consuming a Low-Phenylalanine Diet in Combination with Amino Acid and Glycomacropeptide Medical Foods. J Nutr Metab. 2017;2017:6859820. doi: 10.1155/2017/6859820. Epub 2017 Dec 31.

Stroup BM, Nair N, Murali SG, Broniowska K, Rohr F, Levy HL, Ney DM. Metabolomic Markers of Essential Fatty Acids, Carnitine, and Cholesterol Metabolism in Adults and Adolescents with Phenylketonuria. J Nutr. 2018 Feb 1;148(2):194-201. doi: 10.1093/jn/nxx039.

Stroup BM, Hansen KE, Krueger D, Binkley N, Ney DM. Sex differences in body composition and bone mineral density in phenylketonuria: A cross-sectional study. Mol Genet Metab Rep. 2018 Feb 3;15:30-35. doi: 10.1016/j.ymgmr.2018.01.004. eCollection 2018 Jun.

Other Publications:

van Calcar SC, MacLeod EL, Gleason ST, Etzel MR, Clayton MK, Wolff JA, Ney DM. Improved nutritional management of phenylketonuria by using a diet containing glycomacropeptide compared with amino acids. Am J Clin Nutr. 2009 Apr;89(4):1068-77. doi: 10.3945/ajcn.2008.27280. Epub 2009 Feb 25. Erratum In: Am J Clin Nutr. 2010 Apr;91(4):1072.

Ney DM, Gleason ST, van Calcar SC, MacLeod EL, Nelson KL, Etzel MR, Rice GM, Wolff JA. Nutritional management of PKU with glycomacropeptide from cheese whey. J Inherit Metab Dis. 2009 Feb;32(1):32-9. doi: 10.1007/s10545-008-0952-4. Epub 2008 Oct 29.

Ney DM, Hull AK, van Calcar SC, Liu X, Etzel MR. Dietary glycomacropeptide supports growth and reduces the concentrations of phenylalanine in plasma and brain in a murine model of phenylketonuria. J Nutr. 2008 Feb;138(2):316-22. doi: 10.1093/jn/138.2.316.

MacLeod EL, Clayton MK, van Calcar SC, Ney DM. Breakfast with glycomacropeptide compared with amino acids suppresses plasma ghrelin levels in individuals with phenylketonuria. Mol Genet Metab. 2010 Aug;100(4):303-8. doi: 10.1016/j.ymgme.2010.04.003. Epub 2010 Apr 14.

Laclair CE, Ney DM, MacLeod EL, Etzel MR. Purification and use of glycomacropeptide for nutritional management of phenylketonuria. J Food Sci. 2009 May-Jul;74(4):E199-206. doi: 10.1111/j.1750-3841.2009.01134.x.

• Responsible Party: University of Wisconsin, Madison
• ClinicalTrials.gov Identifier: NCT01428258
• Other Study ID Numbers: H-2010-0165; 1R01FD003711-01A1 ( U.S. FDA Grant/Contract )
• First Posted: September 2, 2011
• Results First Posted: March 3, 2017
• Last Update Posted: August 24, 2018
• Last Verified: July 2018

Individual Participant Data (IPD) Sharing Statement:

• Plan to Share IPD: No

Keywords provided by University of Wisconsin, Madison:

Diet therapy; Low phenylalanine diet; Attention; Executive function

Additional relevant MeSH terms:

Phenylketonurias; Brain Diseases, Metabolic, Inborn; Brain Diseases, Metabolic; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Amino Acid Metabolism, Inborn Errors; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Coal Tar; Keratolytic Agents; Dermatologic Agents