Urinary metabolic profiles in human and rat of 1,2-dimethyl- and 1,2-diethyl-substituted 3-hydroxypyridin-4-ones.

The urinary metabolic profiles of two novel orally active iron chelators, 1,2-dimethyl-3-hydroxypyridin-4-one (CP20 or L1) and 1,2-diethyl-3-hydroxypyridin-4-one (CP94), have been studied in rats. The metabolism of CP20 was also studied in humans. Four novel metabolites of CP20, and a further three metabolites of CP94 were characterized. CP20 was found to undergo extensive phase II metabolism at the 3-hydroxy position, forming predominantly the O-glucuronide, which accounted for 44% of the dose administered in rat and greater than 85% of the dose administered in man. The 3-O-methylated CP20 metabolite (metabolite I) accounted for 1% of the administered dose in both species, whereas the unmetabolized CP20 amounted to 10.5% and 4% of the dose administered in the rats and man, respectively. In contrast, CP94 was extensively hydroxylated at the 2-ethyl position to give its 2-(1-hydroxyethyl) metabolite in the rat, which accounted for 40% of the administered dose. The O-glucuronide metabolite of CP94 accounted for 13.8% of the administered dose, whereas the unmetabolized CP94 amounted to 6.9% of the administered dose. At 72 hr, urinary levels of CP20 and CP94 and their metabolites in the rat accounted for about 55-60% of the administered dose. A large portion of the dose is therefore probably eliminated via the bile. The identity of the above metabolites was established using a combination of two or more of the following techniques: fast atom bombardment-mass spectroscopy, LC-MS, UV-VIS spectroscopy, NMR spectroscopy, specific enzyme hydrolysis assays, and chemical synthesis of compounds.