Determination of the heat shock protein 90 inhibitor 17- dimethylaminoethylamino-17-demethoxygeldanamycin in plasma by liquid chromatography-electrospray mass spectrometry

A rapid method was developed for the quantitative determination of the novel heat shock protein 90 inhibitor, 17-dimethylaminoethylamino-17- demethoxygeldanamycin (17-DMAG; NSC707545), in human plasma. Calibration curves were constructed, and were analyzed using a weight factor proportional to the nominal concentration. Sample pretreatment involved a one-step extraction with ethyl acetate of 0.5-ml samples. The analysis was performed in the range of 1-100 ng/ml on a column (75 mm x 2.1 mm internal diameter with 3.5 μm C18 particle size), using 55% methanol in water containing formic acid as the mobile phase. The column effluent was monitored by mass spectrometry with positive electrospray ionization. The values for precision and accuracy were always <8% and <10% relative error, respectively. The method was successfully applied to examine the pharmacokinetics of 17-DMAG in a cancer patient.