Targeting Mutant Phenylalanine Hydroxylase With Pyrimidine–Triazole Conjugates: A Primary Framework for Candidate Chaperone‐Based Strategies in Phenylketonuria

Phenylketonuria (PKU) is a rare metabolic disorder caused by pathogenic mutations in the phenylalanine hydroxylase (PAH) gene, which impair the conversion of phenylalanine to tyrosine, leading to subsequent neurotoxicity. Dietary management, sapropterin dihydrochloride, and pegvaliase are the current therapies; however, their limited efficacy and adverse effects highlight the pressing need for pharmacological treatments that restore PAH activity. Therefore, in this work, we designed and synthesized pyrimidine–triazole derivatives (Pyr‐TZ) as candidate pharmacological chaperones targeting the catalytic domain of PAH. Molecular docking disclosed that Pyr‐TZ‐2O and Pyr‐TZ‐2S exhibited higher binding energies (−8.5 to −10.3 kcal/mol) for the wild‐type (WT) and mutant (R252Q) PAH compared to sapropterin (−7.0 kcal/mol). Molecular Mechanics with Generalized Born and Surface Area solvation (MM‐GBSA) was used here as comparative estimates suggested enhanced binding stability of Pyr‐TZ compounds, primarily driven by van der Waals and lipophilic interactions. Drug‐likeness and ADMET profiling indicated favorable pharmacokinetic properties. Biological validation in R252Q mutant cells demonstrated significant upregulation of PAH and key tetrahydrobiopterin (BH 4 ) pathway genes, including quinonoid dihydropteridine reductase (QDPR), sepiapterin reductase (SPR), and 6‐pyruvoyl‐tetrahydropterin synthase (PTS), following Pyr‐TZ‐2O treatment. Consistent with these findings, sandwich ELISA revealed a dose‐dependent increase in PAH protein abundance post‐Pyr‐TZ‐2O treatment. Conclusively, Pyr‐TZ‐2O can be considered a potential pharmacological chaperone capable of stabilizing mutant PAH and enhancing cofactor regeneration, offering a rational therapeutic approach for PKU.