TY - JOUR T1 - In Vitro Hepatic Uptake in Human and Monkey Hepatocytes in the Presence and Absence of Serum Protein and Its In vitro to In vivo Extrapolation JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.120.000163 SP - DMD-AR-2020-000163 AU - Xiaomin Liang AU - Yeojin Park AU - Natalie DeForest AU - Jia Hao AU - Xiaofeng Zhao AU - Congrong Niu AU - Kelly Wang AU - Bill J Smith AU - Yurong Lai Y1 - 2020/01/01 UR - http://dmd.aspetjournals.org/content/early/2020/10/09/dmd.120.000163.abstract N2 - It is well documented that human hepatic clearance based on in vitro metabolism or transporter assays systematically resulted in underprediction; therefore, large empirical scalars are often needed in either static or physiologically based pharmacokinetic (PBPK) models to accurately predict human pharmacokinetics (PK). In our current investigation, we assessed hepatic uptake (CLint,uptake) in hepatocyte suspension in Krebs-Henseleit buffer (KHB) in the presence and absence of serum. The results showed that the unbound intrinsic active CL (CLu,int,active) values obtained by normalizing the unbound fraction in the buffer containing 10% serum were generally higher than the CLu,int,active obtained directly from protein free buffer, suggesting "protein-facilitated" uptake. The differences of CLu,int,active in the buffer with and without protein ranged from 1 to 925 folds and negatively correlated to the unbound serum binding of OATP substrates. When using the uptake values obtained from buffer containing serum versus serum-free buffer, the median of scaling factors (SFs) for CLu,int,active reduced from 24.2 to 4.6 and 22.7 to 7.1 for human and monkey respectively, demonstrating the improvement of in-vitro-to-in-vivo extrapolation (IVIVE) in a PBPK model. Furthermore, CLu,int,active were significantly higher in monkey hepatocytes than that in human, and the species differences appeared to be compound-dependent. Scaling-up in vitro uptake values derived in assays containing species-specific serum can compensate the species-specific variabilities when using cynomolgus monkey as a probe animal model. Incorporating SFs calibrated in monkey and together with scaled in vitro data can be a reliable approach for the prospective human PK prediction in early drug discovery. Significance Statement We investigated the protein effect on hepatic uptake in human and monkey hepatocytes and improved the IVIVE using parameters obtained from the incubation in the present of serum protein. In addition, significantly higher active uptake clearances were observed in monkey hepatocytes than in human, and the species differences appeared to be compound-dependent. The PBPK model that incorporates SFs calibrated in monkey and together with scaled in vitro human data can be a reliable approach for the prospective human PK prediction. ER -