Development and Clinical Application of a Simultaneous Liquid Chromatography–Tandem Mass Spectrometry Method for Patients with Graft-versus-Host Disease to Quantify the Plasma Concentrations of Ruxolitinib and Posaconazole

Graft-versus-host disease (GVHD) is a clinically significant problem with high mortality that is gradually increasing. Ruxolitinib (RUX) is the only drug used for steroid-refractory GVHD treatment and is thereby crucial. Therapeutic drug monitoring of RUX may be effective because of the relationship between the plasma RUX concentration and treatment outcomes. Posaconazole (PCZ) has also been the recent focus of combined treatment with RUX owing to its pharmacokinetics. We established a simultaneous LC-tandem MS (LC-MS/MS) method and performed plasma drug concentration measurements and monitoring using clinical laboratory values for both RUX and PCZ. We also compared our technique to a simple LC-MS/MS method for clinical application. Moreover, the utility of the automated pretreatment LC-MS/MS (auto-LC-MS/MS) method was tested for further applications. The simultaneous quantification LC-MS/MS method satisfied analytical validation criteria under clinical conditions. Our method demonstrated linearity over the range of 0.3-500 ng/mL for RUX and 3-5000 ng/mL for PCZ, with intra- and inter-day precision and accuracy within ±15%. A possible correlation between plasma RUX concentration and kidney injury was observed in 1 of the 6 patients. Notably, plasma PCZ concentrations were decreased by changing the administration route. Moreover, the plasma concentration levels obtained using the auto-LC-MS/MS method were highly concordant with those obtained using the LC-MS/MS method. The validated LC-MS/MS method was found to be useful in clinical applications; thus, further research into its applications in clinical practice is desirable.