RESUMEN
BACKGROUND: Phenylketonuria (PKU) is an autosomal recessive inherited disease associated with impaired metabolism of the amino acids phenylalanine (Phe) and tyrosine. The main criterion for diagnosis of PKU is high blood Phe level determined during neonatal screening. In case where PKU patient is responsive to tetrahydrobiopterin treatment, sapropterin restores the impaired activity of the enzyme phenylalanine hydroxylase, resulting in the stimulation of normal Phe metabolism and thereby enhancing patient tolerance to natural products. AIM: The present open, non-comparative clinical study was initiated to assess the degree and frequency of response after 8-day sapropterin administration and assess the safety of 6-week sapropterin treatment in patients with PKU and hyperphenylalaninemia. PATIENTS AND METHODS: The study enrolled 90 patients with PKU. The criterion of response to 8-day sapropterin therapy was the reduction of Phe blood levels ≥ 30% compared with the baseline value. RESULTS: Positive response to treatment was observed in 30 (33.3%) patients (95% CI 23.7-44.1). The mean percentage change in Phe blood levels after the 8-day response test period compared to Phe levels prior to dosing was 14.1 ± 28.4% in the overall subject population (95% CI 8.2-20.1) and 44.3 ± 15.1% in the subpopulation of patients with a positive response (95% CI 38.6-49.9). During the study, adverse events were reported in 24 (26.7%) patients in the overall population in 16 (53.3%) patients in the subpopulation who had a response. CONCLUSION: The study results confirmed the efficacy and safety of sapropterin therapy in patients with PKU, which is consistent with international clinical trials data.