Identification of UDP-glucuronosyltransferases involved in the human hepatic metabolism of GV150526, a novel glycine antagonist.

The major metabolic pathway for elimination of GV150526 is by glucuronidation exerted by glucuronosyl transferases (UGTs). Potential exists for the modification of GV150526 pharmacokinetics by drugs capable of inhibiting the glucuronidation of GV150526. Using human liver microsomes, 44 compounds were screened for inhibition of GV150526 glucuronidation. These compounds were selected because they are extensively glucuronidated themselves or are used as concomitant medication in the treatment of acute stroke. For 11 compounds out of the 44, full inhibition kinetics were performed to determine their Ki-value and mechanism of inhibition. To predict possible in vivo drug-drug interactions, the theoretical percentage of inhibition (i) was determined, based on in vitro determined Ki-values, and the expected Cmax plasma levels of GV150526 and the inhibitor. Of the 11 compounds examined, only propofol had an i-value of 6.6; for all other compounds i-values were lower than 2.1. These results indicate that although in vitro inhibition is observed, the likelihood of in vivo drug-drug metabolic interactions occurring is low. The inhibition results suggest that in addition to UGT1A1, also UGT1A3, UGT1A8/9, and UGT2B4 are involved in the glucuronidation of GV150526. The involvement of UGT1A1 and UGT1A8/9 was confirmed from studies using cDNA expressed human UGT cell lines.