PKU Microtablets Case Studies

Evaluating the Adherence, Tolerance, Acceptability and Safety of a New Amino Acid Based, Microtablet Protein Substitute in PKU: a Case Study Series

Phenylalanine (Phe) free protein substitutes are typically presented in ready to drink liquid or powder format and are made up with water to a set volume. Despite recent advancements related to the taste, scent and texture of commercially available protein substitutes, a proportion of PKU patients choose to consume tablet-based protein substitutes. Protein substitutes in tablet format may help overcome taste, scent and texture concerns associated with powdered and liquid preparations. Indeed, previous research has shown that protein substitute tablets are an effective strategy to manage PKU in children, teenagers and adults. Nonetheless, the daily burden and discipline required often impedes compliance, especially alongside the restrictive low-protein diet. Achieving compliance with multivitamin supplements when given alongside protein substitutes therefore becomes especially challenging. This is particularly true for adolescent, adult and maternal populations.

PKU Microtablets have recently been developed. PKU Microtablets are a new phenylalanine-free tablet protein substitute combined with vitamins, minerals and trace elements. As patient acceptability is fundamental to the successful use of any protein substitute, investigation is needed to assess the compliance, tolerance and acceptability of PKU Microtablets as part of a low phenylalanine dietary regimen in PKU patients.

This series of case-studies aims to evaluate the gastrointestinal tolerance, acceptability, compliance, and safety of this protein substitute in both adults and children from 4 years. These case studies will last 29 days in total, including a 1-day baseline period followed by a 28-day intervention period. The case studies will be conducted across multiple specialist metabolic centres in the UK.

Study Overview

• Status: Not yet recruiting
• Conditions: Phenylketonuria (PKU)
• Intervention / Treatment: Dietary supplement: PKU Microtablet protein substitute

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ellen Taylor; Phone Number: +447900724091; Email: ellen.taylor@nutricia.com

Study Locations

• United Kingdom
  • Bristol, United Kingdom
    • University Hospitals Bristol and Weston NHS Foundation Trust

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Male or female
• Over 4 years of age
• Patients diagnosed with any phenotype of PKU characterised by hyperphenylalaninaemia
• Have been compliant in taking at least one protein substitute, providing at least 20g protein equivalent, for at least 1 month prior to trial commencement
• Have a prescribed daily phenylalanine allowance for PKU
• Written or electronic informed consent from patient, and/or from parent/caregiver if applicable
• Participants who are anticipated to be able to take at least 20g protein equivalent of the case study product per day

Exclusion Criteria:

• Pregnant or lactating
• Requiring parenteral nutrition
• Major hepatic or renal dysfunction
• Participation in other studies within 1 month prior to entry of this study
• Allergy to any of the study product ingredients
• Investigator concern around willingness/ability of patient or parent/caregiver to comply with protocol requirement
• Treatment with Sapropterin dihydrochloride for less than 6 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: PKU Microtabet intervention product; Dietary Supplement: PKU Microtablet intervention product	Dietary supplement: PKU Microtablet protein substitute; PKU Microtablet intervention product

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Gastro-intetsinal tolerance	GI tolerance will be recorded by the Dietitian at baseline on Day 1 and at the end of the case study period (Day 29). GI tolerance will be recorded using a standardised questionnaire to capture perceived severity (none, mild, moderate or severe) of common gastrointestinal symptoms (diarrhoea, constipation, bloating, abdominal discomfort, vomiting and nausea).	Measured at baseline (day 1) and end of intervention (day 29)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Compliance	Compliance with the recommended intake of the patients' usual protein substitute (during baseline) and with the study product (during the case study period) will be assessed by the Dietitian at baseline (Day 1) and at the end of the case study (Day 29). Patients and/or parents/caregivers will be asked to recall the amount of their protein substitute taken in the past 24 hours and on average. This will be compared to the amount recommended to be consumed by their Dietitian. The daily amount prescribed by the Dietitian managing the patient's care will be recorded at the start of the case study and any changes to this prescription during the case study will also be noted.	Measured at baseline (day 1) and end of intervention (day 29)
Acceptability	Acceptability (ease of use and liking) of the patients' usual protein substitute and the study product will be assessed by the Dietitian at baseline (Day 1) and the end of the case study period (Day 29) by a series of questions posed to the patient and/or parent/caregiver. Acceptability questions will assess the patient's sensory experience, ease of use, tolerance, and overall self-rated acceptability on a 5-point Likert scale from Terrible (worst) to Great (best).	Measured at baseline (day 1) and end of intervention (day 29)
Blood Phe and Tyrosine	Participants will be required to provide a total of two fasting fingerprick blood samples as dried blood spots; one on the first day of the intervention period (Day 2) before consuming any of the case study product, and one at the end of the intervention period (Day 29). These tests will be conducted in addition to any usual blood tests the participants conduct as part of their usual disease management, which vary in frequency with the age of the participant and the local policy. Dietitians will also be asked to describe the patient's metabolic control during the case study period.	Day 2 (baseline) and day 29 (end of intervention)
Anthropometry - Height	Height will be measured, using standard methods, recorded to the nearest 0.1cm (at baseline only) and used to calculate body mass index (BMI, kg/m2).	Day 1 (baseline) and day 29 (end of intervention)
Anthropometry - Weight	For safety purposes, at baseline (Day 1) and at the end of the case study (Day 29), body weight (kg) will be measured where possible using standard methods, recorded to the nearest 0.1kg using a weighing scale without heavy clothing.	Day 1 (baseline) and day 29 (end of intervention)
Patient History	A detailed patient history will be recorded at baseline to assess previous compliance to protein substitutes, relevant medical and clinical issues, medication(s) prescribed, and any other relevant information related to the patient's condition or dietary management.	Day 1 (baseline) and day 29 (end of intervention)
Safety/ Adverse events	All adverse events will be recorded, throughout the case study.	Throughout the case study series (day 1 to day 29).

Collaborators and Investigators

• Sponsor: Nutricia UK Ltd
• Investigators: Study Director: Gary Hubbard, Dr, Nutricia, Inc.

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): July 1, 2027

Study Registration Dates

• First Submitted: June 17, 2026
• First Submitted That Met QC Criteria: June 23, 2026
• First Posted (Actual): June 26, 2026

Study Record Updates

• Last Update Posted (Actual): June 26, 2026
• Last Update Submitted That Met QC Criteria: June 23, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Brain Diseases, Metabolic, Inborn; Brain Diseases, Metabolic; Amino Acid Metabolism, Inborn Errors; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Nutritional and Metabolic Diseases; Phenylketonurias
• Other Study ID Numbers: PKUM2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No