RT Journal Article SR Electronic T1 FORMATION AND PROTEIN BINDING OF THE ACYL GLUCURONIDE OF A LEUKOTRIENE B4 ANTAGONIST (SB-209247): RELATION TO SPECIES DIFFERENCES IN HEPATOTOXICITY JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 271 OP 281 DO 10.1124/dmd.104.001677 VO 33 IS 2 A1 Jane R. Kenny A1 James L. Maggs A1 Justice N. A. Tettey A1 Andrew W. Harrell A1 Steven G. Parker A1 Stephen E. Clarke A1 B. Kevin Park YR 2005 UL http://dmd.aspetjournals.org/content/33/2/271.abstract AB SB-209247 [(E)-3-[6-[[(2,6-dichlorophenyl)-thio]methyl]-3-(2-phenylethoxy)-2-pyridinyl]-2-propenoic acid], an anti-inflammatory leukotriene B4 receptor antagonist, was associated in beagle dogs but not male rats with an inflammatory hepatopathy. It also produced a concentration-dependent (10-1000 μM) but equal leakage of enzymes from dog and rat precision-cut liver slices. The hepatic metabolism of SB-209247 was investigated with reference to the formation of reactive acyl glucuronides. [14C]SB-209247 (100 μmol/kg) administered i.v. to anesthetized male rats was eliminated by biliary excretion of the acyl glucuronides of the drug and its sulfoxide. After 5 h, 1.03 ± 0.14% (mean ± S.E.M., n = 4) of the dose was bound irreversibly to liver tissue. The sulfoxide glucuronide underwent pH-dependent rearrangement in bile more rapidly than did the SB-209247 conjugate. [14C]SB-209247 was metabolized by sulfoxidation and glucuronidation in rat and dog hepatocytes, and approximately 1 to 2% of [14C]SB-209247 (100 μM) became irreversibly bound to cellular material. [14C]SB-209247 sulfoxide and glucuronide were the only metabolites produced by dog, rat, and human liver microsomes in the presence of NADPH and UDP-glucuronic acid (UDPGA), respectively. Vmax values for [14C]SB-209247 glucuronidation by dog, rat, and human microsomes were 2.6 ± 0.1, 1.2 ± 0.1, and 0.4 ± 0.0 nmol/min/mg protein, respectively. Hepatic microsomes from all three species catalyzed UDPGA-dependent but not NADPH-dependent irreversible binding of [14C]SB-209247 (100-250 μM) to microsomal protein. Although a reactive acyl glucuronide was formed by microsomes from every species, the binding did not differ between species. Therefore, neither the acute cellular injury nor glucuronidation-driven irreversible protein binding in vitro is predictive of the drug-induced hepatopathy. The American Society for Pharmacology and Experimental Therapeutics