Phase 2 Study of Glycomacropeptide Versus Amino Acid Diet for Management of Phenylketonuria (PKU)
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|ClinicalTrials.gov Identifier: NCT01428258|
Recruitment Status : Completed
First Posted : September 2, 2011
Results First Posted : March 3, 2017
Last Update Posted : August 24, 2018
|Condition or disease||Intervention/treatment||Phase|
|Phenylketonuria||Other: GMP Diet/GMP Medical Foods Other: AA Diet/AA Medical Foods||Not Applicable|
|Study Type :||Interventional (Clinical Trial)|
|Actual Enrollment :||32 participants|
|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)|
|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|
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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
- 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.
To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01428258
|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|
|Study Director:||Denise M Ney, PhD, RD||Professor of Nutritional Sciences, University of Wisconsin-Madison|