Determination of total and unbound docetaxel in plasma by ultrafiltration and UPLC-MS/MS: application to pharmacokinetic studies

Abstract

A sensitive and specific liquid chromatographic/tandem mass spectrometric (LC-MS/MS) method was developed and validated for quantifying total and unbound docetaxel drug concentrations in plasma. Calibration curves for unbound and total docetaxel were linear over the respective ranges of 0.108~10.8 and 0.54~216 ng/mL. The intra- and interday assay accuracy and precision did not exceed 15%. The methods were validated to show the standard range linearity, sensitivity, selectivity, accuracy, precision, and stability of docetaxel in the matrices tested. In addition, this method is fast and simple with a short run time of 4.5 min and a small plasma sample volume (500 µL). The validated method was successfully applied to a pharmacokinetic study of a docetaxel micelle formulation in rat plasma after intravenous administration at a dose of 10 mg/kg. Docetaxel micelles slowly released their drug payload, and protein-bound, unbound, and micellar drug pools existed simultaneously. These various forms in plasma pools were also measured in the study. We confirmed that most of the docetaxel in plasma was micelle-associated (96.52% at 24 h and 83.14% at 72 h) after micellar docetaxel administration, as a result of sequestration of the drug in long-circulating micelles.

A Sensitive Assay for Unbound Docetaxel Using Ultrafiltration plus HPLC-MS and Its Application to a Clinical Study

“…Validated methods to quantify unbound docetaxel have been reported previously; however, the lowest level of quantification was 0.1-0.4 ng/mL [16,17]. Here, we report the successful development of a slightly more sensitive assay to quantify unbound docetaxel with an LLOQ of 0.084 ng/mL in plasma samples from patients receiving oDox+E.…”

“…Previous assays developed to quantify unbound docetaxel utilised equilibrium dialysis or ultrafiltration to separate the unbound docetaxel followed by HPLC-MS/MS [14][15][16]. These methods report a lower limit of quantification (LLOQ) of 0.1 ng/mL to 0.4 ng/mL [14,16,17]. Given the small starting dose of oDox+E (75 mg/m 2 ), we aimed to develop a more sensitive assay to quantify smaller concentrations of unbound docetaxel.…”

Bispecific antibodies (anti-mPEG/anti-HER2) for active tumor targeting of docetaxel (DTX)-loaded mPEGylated nanocarriers to enhance the chemotherapeutic efficacy of HER2-overexpressing tumors

“…Along with the plasma DTX concentration illustrated by Figure S3 is the binding activity of HER2-L sb MDDs remained in the plasma at each time point. Since it has been confirmed that after administration of DTX-loaded L sb MDDs, most of DTX in the plasma was encapsulated in L sb MDDs (Sheu et al., 2017 ). Therefore, the binding activity of HER2-L sb MDDs that encapsulated DTX was measured at the same DTX concentration (all were diluted to 5 ng/mL DTX) as an indication of the same HER2-L sb MDDs concentration being loaded in the measurement of the binding activity.…”