LAUSR

The purpose of this work was to develop and validate a rapid, sensitive and robust liquid chromatography tandem mass spectrometric method for the quantification of β-lapachone in human plasma and to use that method to analyze human clinical samples. Sample preparation for the developed method involved liquid-liquid extraction using ethyl acetate for extraction of β-lapachone and cryptotanshinone (internal standard) from human plasma. Chromatographic resolution was achieved on a Kinetex C18 column using a gradient elution and a chromatographic flow rate of 0.5 mL/min. The retention times of β-lapachone and cryptotanshinone were 1.98 and 2.28 min, respectively, and the method had a total run time of 4 min. Bioanalytical method validation was conducted in accordance with the United States Food and Drug Administration regulatory guidelines. The method was validated over 2 calibration ranges in order to support high- and low-dose clinical studies. Calibration curve-1 covered the range of 0.25-50 ng/mL and calibration curve-2 covered the range of 50-2000 ng/mL. The method was determined to be accurate (percent relative errors between -1.07 to 5.36 %), precise (percent relative standard deviations less than 7.4), and sensitive (LLOQ 0.25 ng/mL). β-lapachone was determined to be stable (% change from time = 0 between -11.6 and 12.6 %) across the autosampler, benchtop, freeze/thaw and long-term (63 days) stability studies. The validated bioanalytical method was employed to determine β-lapachone concentrations in human plasma samples from a clinical study.