Metabolism and pharmacokinetics of p-(3,3-dimethyl-1-triazeno) benzoic acid in M5076 sarcoma-bearing mice

Summary The pharmacokinetics of the anticancer agent p-(3,3-dimethyl-1-triazeno) benzoic acid (pCOOH-DMT), a drug now in phase I clinical trial in Europe, was investigated in C57 Bl female mice with M5076 reticulum-cell sarcoma that were treated i.v. with 200 mg/kg pCOOH-DMT. The drug disappeared from plasma with a terminal half-life of about 2.5 h. Plasma clearance was approximately 6 ml/min per kg. Distribution studies showed some differences in drug levels in different tissues. The highest levels were found in the tumor, liver, kidney and lung; lower levels were found in the spleen and gut, and the lowest, in the brain. The N-desmethyl derivative of pCOOH-DMT was not detectable in plasma or tissues of mice treated with the drug. Therefore, the previous evidence of low N-demethylation of pCOOH-DMT was confirmed. pCOOH-DMT glucuronide was identified by mass spectrometry and quantified by high-performance liquid chromatography (HPLC) in plasma, tissues and urine samples. pCOOH-DMT glucuronide appears to be the major urinary metabolite of pCOOH-DMT in mice. Another metabolite identified by mass spectrometry and quantified by HPLC in some tissues and urine was pCOOH-DMT glycinate.Abbreviations DTIlC 5-(3,3-dimethyl-l-triazeno)imidazole-4-carboxamide - pCOOH-DMT p-(3,3-dimethyl-l-triazeno)benzoic acid - pCOOH-MMT p-(3-methyl-l-triazeno)benzoic acid - pCONH₂-DMT p-(3,3-dimethyl-l-triazeno)carboxamide - BSTFA N,O-bis(trimethylsilyl)trifluoroacetamide - TMCS trimethylchlorosilane - TLC thin-layer chromatography - FAB fast atom bombardment - EI electron impact - M5 M5076 reticulum-cell sarcoma - t_1/2 beta-half-life - C₀ concentration time 0 - AUC area under the concentration vs time curve - Cl total clearance - V volume of distribution