A prospective, open label, acceptability study to evaluate PKU, MSUD, HCU, TYR and GA express plus in the dietary management of 40 patients with IEM. The following parameters will be assessed: adherence to prescribed dietary intakes, palatability, usability, gastrointestinal tolerance, clinically relevant routine biochemical parameters, timeframe to transition and contribution of the express plus range to overall protein substitute intake over a 28 day period.

This is a prospective acceptability study of the express plus range in 40 participants aged at least three years of age for the dietary management of IEM (PKU, MSUD, HCU, TYR and GA ).

The study will involve a Transition Period where patients will build-up to at least one sachet of express plus per day. During the Transition Period, daily intake of express plus and the patient's other PS will be recorded, including the time taken to consume.

The Transition Period will last a maximum of 6 weeks, after which the patient will enter a 28-day Evaluation Period. During the Evaluation Period, patients will continue to record intakes, as well as GI tolerance and a final evaluation of the product's palatability and usability. Some patients, likely adults, will not require a transition from their original protein substitute to at least one sachet of express plus. These patients can enter the Evaluation Period directly.

The end of the 4-week Evaluation Period is defined as the participant's End of Study. Following this, participants will be followed up as per standard of care. Some of this standard of care data may be relayed to the sponsor for a maximum of 26 weeks. This will last for a maximum of 26 weeks and will involve the collection of routine phe and tyrosine levels, as well as amount of PS prescribed and taken. Information will also be collected from patients regarding the reasons for the success or indeed failure of transition to PKU express plus. This data will come from routine clinical contact and will be recorded by the HCP, rather than by the patient.

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 study product 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 dietary intervention 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 the requirements of the protocol.
• Any co-morbidity/condition which in the opinion of the Investigator, would preclude participation in the study.
• Patients who are currently participating in, plan to participate in, or have participated in an interventional investigational drug, food or medical device trial within 30 days prior to screening.
• Use of additional macro/micronutrient supplements during the study period, unless clinically indicated and prescribed by the investigator (must be recorded in patient case record file).
• Women who are pregnant / breastfeeding at the start of the study or planning to become pregnant during the study period. (N.B.: Women who become pregnant unexpectedly during this study may, in consultation with their doctor, continue on the study's dietary product if they wish but will not have any investigations that would not normally be carried out during pregnancy.)
• Those with allergies to fish, milk or soya.

No plans to share IPD

No masking, product will be given open label