Validation study of assay method for DE-310, a novel polymer-bound camptothecin derivative, and the free drug in mouse plasma by liquid chromatography with fluorimetric detection

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 (G-DX-8951) in mouse plasma. Free DX-8951 and Glycyl-DX-8951 were extracted from plasma by protein precipitation and analyzed by HPLC (Method I). Conjugated DX-8951 was extracted by protein precipitation and digested by using a thermolysin. The productive compound was analyzed by HPLC (Method II). The lower limits of quantitation of DX-8951, Glycyl-DX-8951, and Conjugated DX-8951 were 0.60, and 0.77 ng/ml and 3.45 μg/ml (as DX-8951 equivalent). These two methods showed satisfactory sensitivity, precision, accuracy, recovery, and selectivity.