The in vitro metabolism of GMDTC in liver microsomes of human, monkey, dog, rat and mouse: Metabolic stability assessment, metabolite identification and interspecies comparison

Sodium (S)− 2-(dithiocarboxylato((2 S,3 R,4 R,5 R)− 2,3,4,5,6-pentahydroxyhexyl)amino)− 4(methylthio)butanoate (GMDTC) is a compound that removes cadmium from kidney cells. This study aims to investigate the metabolic stability and metabolite identification of GMDTC in various liver microsomes, including those from human, monkey, dog, rat and mouse. The results show that the T_1/2 values of GMDTC in human, monkey, dog, rat and mouse liver microsomes were 16.54, 18.14, 16.58, 15.16 and 16.00 min, respectively. While the hepatic extraction ratios (ER_h) of GMDTC measured after 60 min incubation in these liver microsomes were 0.82, 0.70, 0.80, 0.75 and 0.79, respectively, indicating that GMDTC exhibits rapid hepatic metabolism and high hepatic clearance with no significant interspecies differences. Subsequent metabolite identification by high-resolution mass spectrometry revealed the presence of three metabolites, designated M1∼M3. The major metabolite products of GMDTC were found to be M1 and M2. The relative abundances of the hydrolysis products (M1 and M2) in human, monkey, dog, rat and mouse liver microsomes were found to be 97.18%, 97.99%, 95.94%, 96.31% and 93.43%, respectively, indicating that hydrolysis is the primary metabolic pathway of GMDTC in liver microsomes in vitro, and with no significant interspecies differences.