Unnur Arna Þorsteinsdóttir, Hrafnhildur L. Runólfsdóttir, Finnur F. Eiríksson, Viðar Örn Eðvarðsson, Runólfur Pálsson and Margrét Þorsteinsdóttir
Background
Adenine phosphoribosyltransferase deficiency (APRTd) is a rare disorder characterized by urinary excretion of the poorly soluble 2,8-dihydroxyadenine (DHA), leading to chronic kidney disease (CKD). Treatment with allopurinol or febuxostat reduces DHA excretion and slows CKD progression. The aim of this work was to develop an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based assay for simultaneous quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in human plasma, for pharmacotherapy monitoring in patients with APRTd.
Methods
The UPLC-MS/MS-based assay was optimized employing the chemometric software Modde Pro 13 (Umetrics, Sweden). The method was validated and used for analysis of plasma samples from both untreated and treated APRTd patients and healthy controls.
Results
Intra- and inter-day accuracy and precision were within ±15% for all analytes, and the analytes were found stable in plasma for 12 months at -80°C. In untreated APRTd patients, the average plasma concentration was 237.1 ng/mL for DHA and 297.2 ng/mL for adenine. In patients treated with allopurinol 400 mg/day or febuxostat 80 mg/day, the average plasma concentration of DHA was 78.8 ng/mL and below limit of quantification, respectively, and 845.6 and 1046.9 ng/mL in case of adenine, respectively. DHA was undetectable in plasma samples from healthy controls. The average plasma concentration of allopurinol, oxypurinol and febuxostat in patients receiving these medications was 1695 ng/mL, 11612 ng/mL and 313 ng/mL, respectively.
Conclusion
The UPLC-MS/MS-based assay provides accurate and precise quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in human plasma, and is being implemented for therapeutic monitoring in APRTd patients.
