Urinary phenylacetylglutamine (U-PAGN) concentration as biomarker for adherence in patients with urea cycle disorders (UCD) treated with glycerol phenylbutyrate.

Urinary phenylacetylglutamine (U-PAGN) concentrations in spot urine samples were analyzed as a dosing biomarker during glycerol phenylbutyrate (GPB) dosing in 68 healthy adults and 66 adult and pediatric patients with urea cycle disorders who participated in GPB clinical trials. Age- and body surface area (BSA)-specific 25th percentile cutoff points for spot U-PAGN concentrations (<~9000 µg/mL for < 2 years old patients, < 7000 µg/mL for > 2 years with BSA ≤ 1.3 m2, and <~5000 µg/mL for > 2 years of age with BSA > 1.3 m2) were determined as an approach to identify patients for whom increased dosing and/or adherence to prescribed dosing should be assessed.