A liquid chromatography-tandem mass spectrometry method for therapeutic drug monitoring of treosulfan.

INTRODUCTION: Treosulfan is an alkylating agent administered before hematopoietic stem cell transplantation. Because pharmacokinetic parameters exhibit interindividual variability, therapeutic drug monitoring may be necessary. In this study, a liquid chromatography-tandem mass spectrometry method for monitoring treosulfan was developed and validated. METHODS: Treosulfan was separated from 25 µL plasma after protein precipitation with acetonitrile. Treosulfan-D4 was used as the internal standard. Separation was performed using an ACQUITY UPLC Ι-Class PLUS System (Waters Corporation) coupled with a Xevo TQ-XS Mass Spectrometer (Waters Corporation). Limit of quantification, selectivity, linearity, imprecision, carryover, matrix effect, and stability were validated according to Clinical and Laboratory Standards Institute guidelines. RESULTS: The mass-to-charge transitions were treosulfan 296.2 > 87.1 and treosulfan-D4 300.2 > 91.1. The total run time was 4 minutes. The limit of quantification of treosulfan was 3.13 µg/mL. The calibration curve was linear in the 3.13 to 100-µg/mL range. The method was adequately selective and without carryover or matrix effect. Treosulfan was stable in plasma for 2 hours at room temperature and for up to 3 days and 1 week when stored at 10 °C and ‒20 °C, respectively. DISCUSSION: Our liquid chromatography-tandem mass spectrometry method for measuring treosulfan met Clinical and Laboratory Standards Institute validation requirements and exhibited robust performance, suggesting its utility for therapeutic drug monitoring in clinics treating patients with treosulfan.