Open-label, Randomized, 2-way Crossover, Monocentric, Controlled Study to Evaluate the Effect on Daily PHE Fluctuation of PKU GOLIKE Versus SoC in Patients With PKU.

The study will consist of a screening visit (V1), two treatment periods with two test days each and a final visit planned at the end of the second treatment period (V2). Test days will occur on two consecutive preferably non-working/school days (T1-T2 and T3-T4,) preferably over two consecutive weeks. Treatment days in the two periods will have to be the same days of the week. T1 should be within two weeks after V1. The study products will be self-administered at home. Following informed consent and verification of eligibility criteria, 20 patients with PKU will be randomized in a 1:1 ratio to one of the following two sequences: AB or BA where A=standard of care and B=PKU GOLIKE. In details: * AB: patients will receive 3 daily self-administrations of their usual standard of care for 2 consecutive days in the first period followed by 3 daily self-administrations of PKU GOLIKE for 2 consecutive days in thesecond period. * BA: patients will receive 3 daily self-administrations of PKU GOLIKE for 2 consecutive days in the first period followed by 3 daily self administrations of their usual standard of care for 2 consecutive days in the second period. No change in the randomization sequence will be allowed. Each patient will follow the same diet in terms of food, calories and nutrients ranges during the first days (T1 and T3) of each period and the same diet during the second days (T2 and T4) of each period, according to the age and body weight of the patient. The days before the test days each patient will follow her/his standard diet. PKU GOLIKE /standard of care will be the only protein substitute allowed on each test day, and no sports activities will be allowed on sampling days. Five blood spots will be collected on the second test day of each period. Timing of self-administrations, meals and blood spots will be standardized 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 an overnight fasting (10 -12 h) and before any food intake. A patient's e-diary will be used to collect information on patient compliance, 24-hour blood spot collections, diet, daily activities, adverse events and event-related 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 e-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. The end of study (V2) will be performed (remotely, by phone) at the end ofthe second treatment period, within 2 weeks after the last test day. Patients prematurely discontinued from the study will be asked to attend (remotely, by phone) a discontinuation visit possibly taking place within 2 weeks from the last test day. At the final/discontinuation visit, the investigator will organize collection of blood spots test and residual PKU GOLIKE product from the patient's domicile through a dedicated courier service. The account of the e-diary will be inactivated.