2-Benzoylpyridine-4-ethyl-3-thiosemicarbazone (Bp4eT) is one of lead compounds from the group of novel antitumor agents derived from thiosemicarbazone. The complex character of their anti-cancer activity mediated by 1) the inhibition of ribonucleotide reductase, 2) the redox activity of its Fe and Cu complexes and 3) the effect on various genes and transcription factors might help to overcome the resistance to standard chemotherapy and improve the survival rate of oncologic patients. However, further progress in development of these novel compounds is strongly dependent on availability of relevant pharmacokinetic data.
The aim of this study was 1) to develop and validate a first LC-MS/MS method for simultaneous determination of Bp4eT and its major metabolites (semicarbazone - M1, amidrazone - M2) in rat plasma and 2) to utilize it in a pilot pharmacokinetic study.
The plasma samples were treated by solid-phase extraction on 96 well plates. The analysis was performed on Discovery HS C18 column (75×4.6 mm, 3 μm, Supelco) using 2 mM ammonium formate and acetonitrile (40:60, v/v) as a mobile phase. Ion-trap MS equipped with ESI was utilized as a detection technique. The method was validated according to FDA guidelines over the concentration range of 0.18-2.80 µM for Bp4eT, 0.02-0.37 µM for M1 and 0.10-1.60 µM for M2. Bp4eT was administered i.v. to rats (dose 3 mg/kg, n=4), plasma was collected and analyzed. The concentration-time profile for Bp4eT and metabolite M2 was obtained and the basic pharmacokinetic parameters for the parent compound were calculated. Current study suggests that following the i.v. administration to rats, Bp4eT is metabolized particularly into amidrazone derivative and its AUC(0-t) is about 20% of that for the parent drug, while the amount of semicarbazone metabolite is negligible (AUC(0-t)<1.5% as compared with Bp4eT).

The study is co-financed by the European Social Fund and the state budget of the Czech Republic. Project no. CZ.1.07/2.3.00/30.0061.