Analytical validation and pilot clinical application of a UPLC-MS/MS method for determining intracellular mycophenolic acid and metabolites in kidney transplant recipients

Abstract

There is no consensus on the strategy for therapeutic drug monitoring of the immunosuppressive drug mycophenolic acid (MPA) in organ transplant recipients. The present study proposes the utilization of ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for determining the concentrations of MPA and its metabolites: 7-O-mycophenolic acid glucuronide (MPAG) and acyl mycophenolic acid glucoside (AcMPAG) in peripheral blood mononuclear cells (PBMCs). We aimed to assess the potential application of monitoring MPA and its metabolite concentrations in PBMCs in the infection after transplantation in Chinese kidney transplant recipients (KTRs). The UPLC-MS/MS method we developed demonstrated good linearity in the quantitative ranges of 0.05–50.00 ng/mL for MPA, 0.50–50.00 ng/mL for MPAG, and 0.10–20.00 ng/mL for AcMPAG. AcMPAG in PBMCs was unstable, degrading significantly after 48 h of storage at −80°C or after 3 freeze-thaw cycles. MPA and MPAG concentrations in KTRs' PBMCs exhibited high inter-individual variability, and the MPA concentration in PBMCs was poorly correlated with that in plasma (rs = 0.206, p = 0.117). Compared with the stable group, the infected group had significantly higher MPA concentration in PBMCs at 2 and 4 h post-dosing and in plasma at 4 h post-dosing (p < 0.05). The receiver operating characteristic (ROC) analysis for post-transplantation infection revealed that PBMCs MPA-C4 and PBMCs-MPA-C2 possessed much better diagnostic efficiency than Plasma-MPA-C4. This method is easy-to-use and reliable, making it a promising clinical quantitative tool for MPA, MPAG, and AcMPAG in PBMCs. PBMC-MPA monitoring may be a potential biomarker for infection monitoring for KTRs.