Inhibition of regorafenib against UDP-glucuronosyltransferases / 药学学报

ABSTRACT

This study was designed to investigate the inhibitory effects of regorafenib (REG) on the catalytic activities of 12 kinds of human UGT isoforms and human liver microsomes (HLM) in vitro. The broader potential of REG to perpetrate drug-drug interactions (DDI) arising from UGT enzyme inhibition is predicted by in vitro-vivo extrapolation (IV-IVE). Fifty mixed HLM and 12 kinds of recombinant UGTs were utilized as enzyme sources to evaluation the inhibitory effects of REG against UGTs. 4-Methylumbelliferone (4-MU) as a nonselective substrate of UGTs except for UGT1A4, N-(3-carboxypropyl)-4-hydroxy-1,8-napht-halimide (NCHN) and N-butyl-4-(4-hydroxyphenyl)-1,8-naphthalimide (NPHN) as the specific fluorescent substrate of UGT1A1, and trifluoperazine (TFP) as the specific substrate of UGT1A4. The half maximal inhibitory concentration (IC50) was calculated via the nonlinear regression analysis using Graphpad Prism 6.0, the inhibition kinetic types were selected and evaluated based on the intersection location of Lineweaver-Burk plot and Dixon plot, and Ki values were determined by the second plot of slopes. The potential DDI risk based on UGT1A1 inhibition was also evaluated through the in vitro parameters. The results demonstrated that REG displayed strong inhibitory effects against UGT1A1, 1A7, 1A9, and 2B7. The IC50 values were from 0.15 to 6.6 μmol·L-1 and Ki values from 0.027 to 14 μmol·L-1. The REG exerted competitive inhibition against UGT1A1-mediated 4-MU-O-glucuronidation and UGT1A1-mediated NPHN-O-glucuronidation, while the inhibition of NCHN-4-O-glucuronide by REG was suited to noncompetitive inhibition in both HLM and recombinant UGT1A1. Likewise, REG exhibited a mixed efficacy in inhibition of UGT1A7-, UGT1A9-, and UGT2B7-catalyzed 4-MU-O-glucuronidation. The AUC ratio of UGT1A1 specific substrates NPHN and NCHN can be increased by 101% to 302% and 13% to 109%, respectively. These results suggest that much caution should be exercised when REG is co-administered with UGT1A1 substrates.