Determination of combretastatin A-4 and its phosphate ester pro-drug in plasma by high-performance liquid chromatography.

High-performance liquid chromatography with both absorbance and fluorescence detection has been applied to the determination of the potential anti-tumour agent combretastatin A-4 and its phosphate ester in murine and human plasma. The presence of different interfering peaks in the two species makes absorbance detection at 295 nm the method of choice for the mouse, and fluorescence detection (295 nm/390 nm) for human plasma. The calibration was linear over the range studied (0.01-50 microM for combretastatin A-4, 0.02-200 microM for combretastatin A-4 phosphate), with quantitation limits of 0.05 microM for both drugs in the mouse, and 0.05 microM and 0.0125 microM for the phosphate ester and free drug, respectively, in human plasma. The method should be useful for pharmacokinetic studies in the forthcoming Phase I clinical trial of combretastatin A-4 phosphate.