Development and Validation of a High Pressure Liquid Chromatography–UV Method for the Determination of Treosulfan and Its Epoxy Metabolites in Human Plasma and Its Application in Pharmacokinetic Studies

Treosulfan (l-threitol-1,4-di-methanesulfonate) is a prodrug of a bifunctional alkylating agent that is being used increasingly in pediatric bone marrow transplantation regimens. The activation pathway is a complex reaction, which consists of two consecutive reactions leading to epoxybutane derivatives which are responsible for DNA alkylation. A simple, sensitive high performance liquid chromatography method for the determination of the sum of treosulfan and its epoxy metabolites by UV detection after derivatization with sodium diethyldithiocarbamate in human plasma was developed and validated. Plasma samples containing treosulfan and epoxy metabolites were converted into thiocarbamate derivative with 10% sodium diethyldithiocarbamate. Dinitrobiphenyl was used as an internal standard. The analysis was carried out using a reversed phase C18 column with a mobile phase consisting of methanol–water (65:35, v/v) at a flow rate of 1 mL/min. The eluent was monitored at 254 nm. The standard calibration curve was established between 2.5 and 50 µg/mL, with a correlation coefficient of 0.9987. Intra- and interday precision and accuracy of the method was