Development and validation of an ultrafiltration-UPLC-MS/MS method for rapid quantification of unbound docetaxel in human plasma

•Docetaxel lipid microsphere is a novel formulation of docetaxel without Tween-80.•Reliable ultrafiltration coupled with UPLC-MS/MS method is firstly developed.•Low LLOQ (0.2 ng/mL) and short chromatographic run time (2.5 min) were achieved.•Much smaller volume of human plasma (only 450 μL) is utilized.•This validated method could be applied to clinical study of docetaxel lipid microsphere.

Docetaxel lipid microsphere (DT-LM) is a novel formulation of docetaxel without Tween-80. A sensitive, robust and reproducible ultrafiltration (UF) followed by UPLC-MS/MS method was developed and validated for the quantification of unbound docetaxel in human plasma using paclitaxel as IS. Ultrafiltrate samples were chromatographed on Acquity UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm). The mobile phase was a mixture of 10 mM ammonium formate in water containing 0.2% formic acid (A) and acetonitrile containing 0.2% formic acid (B). The volume of plasma utilized was only 450 μL. The calibration curve was linear over the range of 0.2–200 ng/mL, with LLOQ of 0.2 ng/mL. The method was shown to be reliable and reproducible with intra- and inter-day precision and accuracy <±15%, and extraction recovery of 98.1–104.8%. Docetaxel was stable during stability studies, e.g., short term, post-preparation and freeze–thaw cycles. The validated method was utilized to support the pharmacological study of DT-LM in patients with advanced cancer.