Determination of BmKCT-13, a chlorotoxin-like peptide, in rat plasma by LC–MS/MS: Application to a preclinical pharmacokinetic study

• A LC–MS/MS method was developed for the quantification of BmKCT-13 in rat plasma.
• Methanol with 0.1% formic acid greatly improved the recoveries of analytes.
• The assay was successfully applied to a preclinical pharmacokinetic study of BmKCT-13 in rats.
• The pharmacokinetic parameters of BmKCT-13 were determined for the first time in rats.

A novel chlorotoxin-like toxin derived from Buthus martensii Karsch, namely BmKCT-13, is a potential candidate for glioma therapy and highly homologous to the chlorotoxin (CTX) derived from the venom of the scorpion Leiurus quinquestriatus. In this study, a simple, sensitive, and robust analytical method based on liquid chromatography–tandem mass spectrometry has been developed for the determination of BmKCT-13 in rat plasma using CTX as internal standard (IS). After sample preparation by protein precipitation with 0.1% formic acid in methanol, chromatography was performed on a Hanbon Dubhe C18 column (150 mm × 2.1 mm, 5 μm, and 100 Å) using a gradient elution with 0.1% formic acid in water and methanol. Mass spectrometry involved positive electrospray ionization and multiple reaction monitoring of the transitions at m/z 780.2→69.9 for BmKCT-13 and m/z 800.2→69.7 for CTX. The method was linear over the concentration range 10–1000 ng/mL with a lower limit of quantification of 10 ng/mL. Intra- and inter-day precision (expressed as relative standard deviation, RSD) were ≤8.1 and ≤7.9%, respectively, with intra-and inter-day accuracy of 94.5–99.0%. Recoveries of BmKCT-13 and IS were more than 65% and matrix effects were not significant. Stability studies showed that BmKCT-13 was stable under a variety of storage conditions. The method was successfully applied to a pharmacokinetic study involving intravenous administration of BmKCT-13 to rats.