Determination of the glucuronide metabolites of the topoisomerase I inhibitors, 7-ethyl-10-hydroxy-camptothecin (SN-38) and NU-ICRF 505 by high performance liquid chromatography

HPLC methods are presented for the determination of the topoisomerase I inhibitors 7-ethyl 10-hydroxycamptothecin (SN-38) and NU/ICRF 505, their chemical/enzymatic hydrolysis products and glucuronide metabolites in both aqueous media and biological specimens. Chromatographic conditions were optimised for baseline resolution of the water-soluble metabolites from their non-water soluble parent compounds while eetaining compatibility with both atmospheric pressure electrospray ionisation and electron impact ionisation mass spectrometric detection. Solid phase extraction sample preparation utilising a C2-bonded silica sorbent enabled simultaneous recovery of parent compounds and metabolites. The methodology was applied to determine the stability of SN-38 in aqueous media and identify the glucuronide metabolites of both compounds in incubations with the drug-metabolising enzyme UDP-glucuronosyltransferase, the de-conjugating enzyme β-glucuronidase and human colon cancer cells.