Höfundar:
Unnur Arna Þorsteinsdóttir, Hrafnhildur L. Runólfsdóttir, Finnur F. Eiríksson, Viðar Ö. Eðvarðsson, Runólfur Pálsson, Margrét Þorsteinsdóttir
Introduction
Adenine phosphoribosyltransferase deficiency (APRTd) is a rare purine metabolism disorder characterized by urinary excretion of the poorly soluble 2,8-dihydroxyadenine (DHA), nephrolithiasis and chronic kidney disease (CKD). Treatment with the xanthine oxidoreductase (XOR) inhibitors allopurinol or febuxostat reduces DHA excretion and slows CKD progression. The aims of the study were to optimize and validate a UPLC-MS/MS method for simultaneous quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in plasma, utilizing design of experiments (DoE).
Methods
The UPLC-MS/MS quantification method was optimized, employing the chemometric software MODDE Pro 13. Fractional factorial design was used to reveal significant experimental factors influencing peak area, retention time and resolution of all analytes using partial least square regression. The method was validated and used for absolute quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in plasma samples from both untreated and treated APRTd patients and healthy controls.
Results
Accuracy and precision were within ±15% for all analytes. The median (range) plasma concentration was 248 (224-395) ng/mL for DHA and 194 (159-284) ng/mL for adenine in untreated patients, and < 100 ng/mL for DHA and 533 (339-1034) ng/mL for adenine in those on treatment. DHA was not detected in plasma samples from healthy controls. The median plasma concentration for allopurinol, oxypurinol and febuxostat in patients receiving XOR inhibitor therapy was 687 (103-2901), 7945 (2199-10943) and 1628 ng/mL, respectively.
Conclusion
The UPLC-MS/MS assay yields accurate quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in human plasma and can be implemented for therapeutic monitoring in patients with APRTd.