Validation study of a method for assaying DE-310, a macromolecular carrier conjugate containing an anti-tumor camptothecin derivative, and the free drug in tumor tissue by high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry

Abstract

DE-310 is a macromolecular carrier conjugate containing an anti-tumor camptothecin derivative, DX-8951, which is conjugated to a water-soluble polymer via a peptide spacer. Assay methods have been developed for the determination of a polymer-bonded DX-8951 conjugate, DX-8951, and Glycyl-DX-8951 concentrations in murine Meth A tumor tissue. Free DX-8951 and Glycyl-DX-8951 were extracted from tumor tissue homogenates by protein precipitation and analyzed by LC/MS/MS (method I). Conjugated DX-8951 was isolated by solid-phase extraction after digestion with a thermolysin. The productive phenylalanyl-glycyl-DX-8951 was analyzed by LC/MS/MS (method II). The lower limits of quantitation of DX-8951, Glycyl-DX-8951, and conjugated DX-8951 were 1.36, 1.34 and 73.7 ng/g (as DX-8951 equivalent). These two methods showed satisfactory sensitivity, precision and accuracy. To study the pharmacokinetics of DE-310, it would be of great help to assay the polymer-bonded DX-8951 and its released drugs in tumor tissue.