DETECTION AND IDENTIFICATION OF HUMAN URINARY METABOLITES OF BIANTRAZOLE (CL-941)

The anthrapyrazole derivative biantrazole amino]ethyl]amino]-anthra[1, 9-cd]pyrazol-6(2H)-one dihydrochloride, CI-941) is currently under cli nical investigation for the treatment of breast cancer. Up to now, pha rmacokinetic data of the drug were acquired using an HPLC assay lackin g the capability to detect and separate metabolites of CI-941. Therefo re an HPLC separation procedure was developed that is compatible with the ionization methods used most frequently for coupling to mass spect rometry. Application of the HPLC analysis to the urine of a patient tr eated with biantrazole clearly demonstrated the presence of two more p olar metabolites. The molecular masses of the metabolites were determi ned during an HPLC-MS coupling with ionspray ionization after injectio n of an extract of only 15 ml of patient urine. Both metabolites have the same UV-VIS spectra as biantrazole and exhibit collision-induced m ass spectra typical for aminoalkylamino-substituted anthrapyrazoles. T he daughter ion mass spectra acquired during the HPLC separation allow ed the identification of the chemical structures of both metabolites. Metabolite 1 was identified as the oxidation product of CI-941 with bo th side chains oxidized at the hydroxymethylene groups to the correspo nding dicarboxylic acid derivative, whereas metabolite 2 was shown to be the analogous monooxidation product. However, the unsymmetrical mol ecular structure of CI-941 did not allow us to distinguish between two possible isomers of metabolite 2. Quantitation of the drug and its me tabolites in patient urine collected during a time period of 100 hr sh owed that 0.55% of the dose were excreted as metabolite 1, 0.34% of th e dose as metabolite 2, and 7.8% of the dose as unchanged drug.