IDENTIFICATION AND QUANTITATIVE-DETERMINATION OF GLUTATHIONE-RELATED URINARY METABOLITES OF FOTEMUSTINE, A NEW ANTICANCER AGENT

1. Potential sulphur-containing metabolites of the anticancer agent, f otemustine, were synthesized, namely thiodiacetic acid (TDA), S-2-hydr oxyethyl N-acetyl-L-cysteine (2-HE-NAC), N-acetyl-L-cysteine (NAC), S- methyl N-acetyl-L-cysteine (M-NAC), S-carboxymethyl-L-cysteine (CM-Cys ), S-carboxymethyl N-acetyl-L-cysteine (CM-NAC), their corresponding s ulphoxides and sulphones. Their chemical structures and stabilities we re confirmed and derivatization methods were developed for their analy sis by sulphur-selective g.l.c. (g.l.c.-FPD) and g.l.c.-mass spectrome try. 2. Four methods for isolation of potential metabolites of fotemus tine were developed. Quantification of metabolites, derived in various ways was carried out by g.l.c.-atomic emission detection (AED) or g.l .c.-mass spectrometry. 3. Male Wistar rats (n=4) were given a single i .p. dose of 40 mg/kg fotemustine. Urine excretion of TDA (18.4+/-1.9% in 24 h) and TDA sulphoxide (12.0+/-1.6% in 24 h) was significant; 32. 7+/-4.6% of the fotemustine dose was excreted as TDA, and TDA sulphoxi de in 48 h. NAC was excreted in rat urine at 1% of the dose. No other potential glutathione-derived metabolites of fotemustine were excreted . 4. Male Wistar rats (n=4) were also treated i.p. with fotemustine at 5, 20 and 40 mg/kg, to investigate dose dependency and the time cours e of excretion of TDA. Excretion of TDA in 48 h urine decreased from 3 2+/-2 to 17+/-2% dose (mean+/-SD) with increasing dose of fotemustine.