IMM-H004, a derivative of
coumarin, is a promising candidate for the treatment of
cerebral ischemia. The pharmacodynamic mechanisms of
IMM-H004 are still under exploration. The present study was conducted to explore the pharmacoactive substances of
IMM-H004 from the perspective of
drug metabolism. Four metabolites of
IMM-H004 including demethylated metabolites M1 and M2,
glucuronide conjugate IMM-H004G (M3), and sulfated conjugate M4 were found in rats in vivo. IMM-H004G was the major metabolite in rats and cultured human hepatocytes, and
uridine diphosphate-
glucuronosyltransferase (UGT) was found to catalyze the metabolism of
IMM-H004 in human liver microsomes (HLMs) and rat liver microsomes (RLMs) with high capacity (V max at 3.25 and 5.04 nmol/min/mg
protein). Among 13 recombinant human UGT
isoforms, UGT1A7, 1A9, 1A8, and 1A1 appeared to be primarily responsible for IMM-H004G formation. The exposure and duration of IMM-H004G (28,948 h × ng/ml of area under the plasma concentration-time curve (AUC), 6.61 h of t 1/2β) was much higher than that of the parent
drug (1,638 h × ng/ml of AUC, 0.42 h of t 1/2β) in transient
middle cerebral artery occlusion/reperfusion (MCAO/R) rats, consistent with the
malondialdehyde (MDA) inhibition effect for at least 10 h. Further pharmacological study revealed that IMM-H004G exhibited a similar neuroprotective activity to that of the parent
drug on both
oxygen-
glucose deprivation injured PC12 cells and transient MCAO/R injured rats. These results demonstrate that both prototype and IMM-H004G are the active
pharmaceutical substances, and IMM-H004G, at least in part, contributes to the maintenance of anti-
cerebral ischemia efficacy of
IMM-H004.