Evaluation of the Express Plus Range

Inclusion Criteria:

• Diagnosis of PKU or associated disorder for example, Tetrahydrobiopterin (BH4)deficiency, requiring a low protein diet and Phe-free L-amino acid supplements (protein substitute).

• Established on PKU express or an equivalent protein substitute

• In the opinion of the study investigator, the participant is able to take the studyproduct and meets at least one of the following criteria:

1. taking an age inappropriate protein substitute

2. struggling with adherence to current protein substitute

3. delayed in transitioning

• Aged 3 years and above

• Willingly given, written, informed consent from patient or parent/guardian.

• Willingly given, written assent (if appropriate).

Exclusion Criteria:

• Diagnosis of persistent hyperphenylalaninaemia, or mild PKU not requiring dietaryintervention with a low protein diet and protein substitute.

• Patients who are tube-fed.

• Individuals, who in the opinion of the investigator, are unable to comply with therequirements of the protocol.

• Any co-morbidity/condition which in the opinion of the Investigator, would precludeparticipation in the study.

• Patients who are currently participating in, plan to participate in, or haveparticipated in an interventional investigational drug, food or medical device trialwithin 30 days prior to screening.

• Use of additional macro/micronutrient supplements during the study period, unlessclinically indicated and prescribed by the investigator (must be recorded in patientcase record file).

• Women who are pregnant / breastfeeding at the start of the study or planning tobecome pregnant during the study period. (N.B.: Women who become pregnantunexpectedly during this study may, in consultation with their doctor, continue onthe study's dietary product if they wish but will not have any investigations thatwould not normally be carried out during pregnancy.)

• Those with allergies to fish, milk or soya.