P332 In vitro characterization of transporters mediating hepatic uptake and biliary excretion of AMG009 in rats

Eskouhie H. Tchaparian , Pkdm, Amgen Inc., South San Francisco, CA
Guifen Xu , Pkdm, Amgen Inc., South San Francisco, CA
Yun Ling , Pkdm, Amgen Inc., South San Francisco, CA
Tom Huang , Pkdm, Amgen Inc., South San Francisco, CA
Mark P Grillo , Pkdm, Amgen Inc., South San Francisco, CA
Lixia Jin , Pkdm, Amgen Inc., South San Francisco, CA
AMG009 is a CRTH2 (chemoattractant receptor-homologous molecule expressed on Th2 cells) and DP (prostanoid D receptor) dual-antagonist with a low to moderate clearance and good bioavailability. AMG009 is eliminated primarily as unchanged drug (52%) and acyl glucuronide M1 (39%) via biliary excretion in rats. Hence, it was hypothesized that hepatic uptake and efflux transporters could play an important role in the disposition and metabolism of AMG009. In the present study, interaction of AMG009 with major rat hepatic transporters were evaluated using 1) rat  primary hepatocytes, 2) stably tranfected cell lines overexpressing rat multidrug resistance protein 1 (Mdr1), multidrug resistance-associated protein 2 (Mrp2),or  breast cancer resistant protein (Bcrp), and 3) xenopus laevis oocytes overexpressing rat organic anion-transporting polypeptide (Oatps), organic anion-transporter (Oat2), or organic cation-transporter (Oct1).  Hepatocytes uptake studies indicated that uptake transport of AMG009 was saturable, and time- and concentration-dependent with an apparent Km value of 187 µM.  Inhibition of AMG009 uptake by chemical inhibitors in primary hepatocytes identified AMG009 as a substrate of Oatps, but not Oct1 or Oat2. Xenopus oocytes uptake studies revealed that AMG009 uptake was mediated by Oatp1 and Oatp2 with Km values of 39 μM and 417μM respectively. Efflux studies identified AMG009 as a substrate of hepatic apical transporters Mdr1 and Mrp2, but not Bcrp. Taken together, these data suggest possible contribution of these transporters in the biliary excretion and hepatic uptake of AMG009. In vivo investigations are underway to determine the significance of transporters in the hepatic metabolism and clearance of this compound in rats.