SIMPLE AND VERSATILE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD FOR THE SIMULTANEOUS QUANTITATION OF THE LACTONE AND CARBOXYLATE FORMS OF CAMPTOTHECIN ANTICANCER DRUGS

The well documented hydrolysis of the alpha-hydroxy-delta-lactone ring moiety in camptothecin and related analogues is routinely monitored u sing high-performance liquid chromatography (HPLC). Previous HPLC sepa rations of the lactone and carboxylate forms of camptothecins have oft en required mobile phases containing three to four components; ion-pai ring reagent to provide adequate retention of the carboxylate form of the drug; buffer to control the ionic strength and pH of the mobile ph ase; acetonitrile to control the retention of the lactone form and, in some instances, sodium dodecyl sulfate to reduce peak tailing. Becaus e of the complexity of the mobile phases employed, development of thes e assays can be a laborious process, requiring re-optimization for eac h new analogue. In this study, we have developed a simple HPLC methodo logy for the simultaneous separation of the lactone and carboxylate fo rms of numerous camptothecin analogues. The mobile phase employed incl udes only triethylamine acetate(TEAA) buffer and acetonitrile. In this application, triethylamine serves multiple roles; as the ion-pairing reagent, as a masking agent for underivatized silanols and as the majo r buffer component. By altering only the composition of TEAA buffer wi th respect to acetonitrile, method development becomes a more streamli ned and time efficient process. In this publication, we present the si multaneous separation of the lactone and carboxylate forms of camptoth ecin and four related analogues, namely, topotecan, GI147211, 10-amino camptothecin and the CPT-11-SN-38 drug-metabolite pair. It is proposed that this new mobile phase, consisting of only triethylamine acetate buffer and acetonitrile, can be used for the analysis of the several c amptothecin derivatives presently in clinical trials as well as the nu merous other analogues in preclinical development.