Targeting phenylalanine assemblies as a prospective disease-modifying therapy for phenylketonuria

Phenylketonuria is characterized by the accumulation of phenylalanine, resulting in severe cognitive and neurological disorders if not treated by a remarkably strict diet. There are two approved drugs today, yet both provide only a partial solution. We have previously demonstrated the formation of amyloid-like toxic assemblies by aggregation of phenylalanine, suggesting a new therapeutic target to be further pursued. Moreover, we showed that compounds that halt the formation of these assemblies also prevent their resulting toxicity. Here, we performed high-throughput screening, searching for compounds with inhibitory effects on phenylalanine aggregation. Morin hydrate, one of the most promising hits revealed during the screen, was chosen to be tested in vivo using a phenylketonuria mouse model. Morin hydrate significantly improved cognitive and motor function with a reduction in the number of phenylalanine brain deposits. Moreover, while phenylalanine levels remained high, we observed a recovery in dopaminergic, adrenergic, and neuronal markers. To conclude, the ability of Morin hydrate to halt phenylalanine aggregation without reducing phenylalanine levels implies the toxic role of the phenylalanine assemblies in phenylketonuria and opens new avenues for disease-modifying treatment.