PEMP-AT is a prospective, single-arm, open-label, 1-week acceptability study to evaluate PKU EASY Microtabs Plus for the dietary management of participants with phenylketonuria (PKU). Up to 10 participants aged 3 years and above will be recruited in a single-centre in the UK.

PKU is a rare inborn error of metabolism with a prevalence of 1 in 10,000 in the UK population. The mainstay of treatment for most individuals is dietary therapy with a strict protein-restricted diet. We propose to recruit children with a diagnosis of PKU aged 3 years and above.

The study product, PKU EASY Microtabs Plus is a food for special medical purposes (FSMP), as defined by the Delegated Act EU 2016/128, used for the dietary management of Phenylketonuria (PKU).

The study will be investigating the acceptability of PKU EASY Microtabs Plus, as defined by the Advisory Committee on Borderline Substances (ACBS). This includes the following:

participant adherence to recommended intakes gastrointestinal symptoms evaluations of palatability. Each participant will be on the study for 1 week.

The study consists of a 1 week period where participants introduce the study product into their diet. Gastrointestinal tolerance, compliance and product acceptability will be evaluated.

Data collection will be performed using paper data collection forms completed by the investigators at the baseline and end of study visits. Patients/parents/guardians, as appropriate, will also complete a brief daily questionnaire on each of the 7 study days. There will also be a questionnaire completed by the patient/parents/guardians over the course of the study, in relation to protein substitute intake, gastrointestinal tolerance, and product acceptability.

Inclusion Criteria:

• Diagnosis of PKU requiring an appropriate protein substitute
• Subjects who are already taking an appropriate protein substitute and are willing to try the study product for 7 days
• Subjects aged 3 years and above
• Written informed consent obtained from subject or parent/legal guardian, depending on subject age

Exclusion Criteria:

• Presence of serious concurrent illness
• Lead Dietitian's uncertainty about the willingness or ability of the patient to comply with the protocol requirements
• Participation in any other studies involving investigational or marketed products concomitantly or within two weeks prior to entry into the study, with the exception of sapropterin
• Any subject having taken antibiotics over the previous 2 weeks leading up to the study
• Subjects less than 3 years of age

Due to the very small number of participants and rarity of the condition being tested the ability to maintain participant pseudonymity could be compromised.