Study to Evaluate the Effect on Nitrogen Retention of Two Different Posology Schemes of PKU GOLIKE PLUS 3-16 and Free AAs in Patients With Phenylketonuria

This is an open-label, randomized, 4-way crossover, monocentric, controlled study in patients (3 ≤ years of age ≤ 20 ) with phenylketonuria (PKU).

The primary comparison will be between the test product (PKU GOLIKE PLUS 3-16, a prolonged-release amino-acids (AAs) mixture, in this protocol referred to as GOLIKE PLUS 3-16) and the reference product (an immediate-release free AAs mixture with the same qualitative and quantitative composition of PKU GOLIKE PLUS 3-16). PKU GOLIKE PLUS 3-16 is a food for special medicinal purposes (FSMP) for the dietary management of PKU.

The study will consist of a screening visit (T0), four test days taking place on Sunday (T1-T4), each separated by a washout period (a period of time when a participant is taken off a treatment in order to eliminate its effects) and with the study products being self-administered at home, and a final visit (T5). A telephone call will be made to the patients during each washout period. Test days will occur preferably on four consecutive weeks with a 1-week washout period between each test day. Washout can be extended up to 2 weeks in case a dose delay (i.e. delay of the test day) is deemed necessary.

Following informed consent and verification of eligibility criteria, 24 patients with PKU will be randomized in a 1:1:1:1 ratio to one of the following four randomization sequences: ABCD, BDAC, DCBA or CADB.

A, B, C and D will be:

1. One day treatment with 3 self-administrations of GOLIKE PLUS 3-16 (1.2 g/kg total daily dose of AA) B. One day treatment with 2 self-administrations of GOLIKE PLUS 3-16 (1.2 g/kg total daily dose of AA) C. One day treatment with 3 self-administrations of free AAs (1.2 g/kg total daily dose of AA) D. One day treatment with 2 self-administrations of free AAs (1.2 g/kg total daily dose of AA) No change in the randomization sequence will be allowed. Diet will be standardized among different patients in terms of calories and nutrients ranges on each test day, according to the age and body weight of the patients. Moreover, the type of food ingested in 24 hours will be the same on each test day in the same patient.

GOLIKE PLUS 3-16 and the free AAs mixture will be the only protein substitute allowed on each test day, and no sports activities will be allowed on the test days.

24-hour urines and five blood spots will be collected on each test day. Timing of self-administrations, meals and blood spots will be defined for each test day. On the test days, no food will be allowed outside of the defined time windows. The first self-administration of each test day will be performed after overnight fasting (10 -12 h) and before any food intake takes place. Urine should be voided before the first self-administration and not collected. 24-hour urine collection begins thereafter.

The day after each test day a designated courier will collect urine samples and blood spots at the patient's home and will bring them to the center.

A patient's diary will be used to collect information on patient compliance, 24-hour urines and blood spot collections, diet, daily activities, adverse events and concomitant medications.

Adverse events will be continuously monitored during the study, starting from informed consent. Adverse events will be collected by the patients (or by a parent/guardian) in the diary and during the telephone calls made by the Investigator to the patients. Moreover, patients (or parents/guardians) will be instructed to promptly report adverse events occurring during the study to the Investigator.

Patients completing all four test days will be asked to go to the center for a final visit (T5) taking place within 2 weeks from the last product administration. Patients prematurely discontinued from the study will be asked to attend a discontinuation visit possibly taking place within 2 weeks from the last product administration. At the final/discontinuation visit, patients will be asked to return their diaries and the Investigator will verify all information reported in the patient's diary and record it in the electronic Case Report Form (eCRF).