P325 Evaluation Of Uptake Transporters In Human Adult And Pediatric Hepatocytes

Michael Hayashi , Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, CA
Andrew Hui , Pkdm, Amgen Inc., Thousand Oaks, CA
Josh DeKeyser , Pkdm, Amgen Inc., Thousand Oaks, CA
Steven Louie , Pkdm, Amgen Inc., Thousand Oaks, CA
Magang Shou , Pkdm, Amgen Inc., Thousand Oaks, CA
Lilly Xu , Pkdm, Amgen Inc., Thousand Oaks, CA

Evaluation of Uptake Transporters in Human Adult and Pediatric Hepatocytes

Mike Hayashi, Andy Hui, Josh Dekeyser, Steve Louie, Magang Shou, and Lilly Xu

Department of Pharmacokinetics and Drug Metabolism, Amgen Inc., Thousand Oaks, CA, USA 91320

The expression and induction of ADME genes in hepatocytes can alter the pharmacokinetic properties of many xenobiotics. An ontogenic switch in expression of CYP3A isoforms from CYP3A7 in pediatrics to CYP3A4 in adults has been observed in humans. Differential expression of ADME genes in adult and pediatric patients could result in differential dosing paradigms in these two patient populations; therefore, the aim of this study was to evaluate the ADME gene expression profiles in adult (AH) and pediatric hepatocytes (PH) treated with and without known CYP inducers. Human hepatocytes from pediatric and adult donors were evaluated in both suspension and plated format for ADME gene expression and transporter uptake activities (OATP1B1/3, OCT1, and OAT2). For the gene expression study, plated cells were treated with omeprazole (OME), Phenobarbital (PB), rifampicin (RIF) or vehicle control (VC) for 48 hours. The relative expression of 22 ADME genes was determined using RT-qPCR. For transporter activity, cells untreated and treated with the inducers (24 and 48 hrs post dosing) were exposed to transporter-specific radiolabelled substrates for 10 min at either 37ēC or 4ēC followed by aspiration and washing 4X with ice-cold hanks balanced salt solution.  Cells were lysed and the uptake of substrates was determined by liquid scintillation and normalized to uptake activity (amount per unit of protein). Our results indicated that the gene expression level of OATP1B1/3, OAT2 and OCT1 in PH has no significant difference compared to AH. The uptake activity of OATP1B1 and OCT1 is significantly lower in PH relative to AH; however at 24 h and 96 h post plating, the uptake in PH is significantly higher than AH.  OATP1B3 uptake in PH is significantly higher than in AH at all time points.  OAT2 uptake is similar in both populations except for that at 24 h post-plating in which uptake in PH is higher. Relative to VC, RIF treatments inhibited uptake for OATP1B3 and OCT1 while OATP1B1 and OAT2 uptake were unchanged.  PB inhibited all transporters relative to VC and there was no difference in uptake between adults and pediatrics.  After 48 h of OME treatment, uptake of OAT1B3 and OCT1 in both AH and PH, OATP1B1 in PH, and OAT2 in AH was shown to be inhibited compared to VC. Differences in ADME gene expression and uptake between the two populations was determined using a Student's t-Test. Modest differences in induced and un-induced ADME gene expression profiles were observed between adult and pediatric hepatocytes; however, there is a significant uptake transporter difference in these two populations.