Determination of Aplidin (R), a marine-derived anticancer drug, in human plasma, whole blood and urine by liquid chromatography with electrospray ionisation tandem mass spectrometric detection

A sensitive and highly specific liquid chromatographic method with electrospray ionisation tandem mass spectrometric detection (LC-ESI-MS/MS) is reported for the determination in human plasma, whole blood and urine of Aplidin(R) (APL), a novel depsipeptide derived from the tunicate Aplidium albicans with a potent cytotoxic activity under investigation in clinical studies. Didemnin B was used as internal standard and, after protein precipitation with acetonitrile and liquid-liquid extraction with chloroform, APL was separated by liquid chromatography using a reversed-phase C-18 column and a linear gradient of acetonitrile in water (both containing 0.5% formic acid). Detection was performed using a turboionspray source operated in positive ion mode and by multiple reaction monitoring (MRM; m/z 1111--> 295 for APL and m/z 1113 --> 297 for didemnin B). The method was linear (r greater than or equal to 0.9933) over the range 1-250ng/ml, with intra- and inter-batch precision and accuracy below 12.2% (except at LLOQ, less than or equal to 15.4%) for both plasma and urine. Recoveries were moderate, ranging from 54 to 70% in plasma and blood, and from 46 to 60% in urine, for both APL and didemnin B. The LOD was 0.25 ng/ml for both matrices. APL resulted stable in the different matrices at least for 6 h (both at room temperature and 37 degreesC), after freeze and thaw cycles and long term storage at -20degreesC. The method allowed demonstrating that APL is in a dynamic equilibrium between plasma and blood cells. Moreover, the method was successfully applied to the pharmacokinetic study of Aplidino in cancer patients. (C) 2003 Elsevier B.V. All rights reserved.