HP1 Heps-s Human Primary Hepatocytes-Single Donor

Comparison of Initial Uptake Clearance, C/M Ratio, and Tissue Unbound Fraction (fT) of the Six Anionic Compounds between PHH and SHH.

Among the various in vitro hepatocyte models currently established, suspended human hepatocytes (SHH) are utilized for assessing drug uptake and metabolism, while primary human hepatocytes (PHH) are used for the evaluation of drug uptake, basolateral efflux, and metabolism. These models exhibit different advantages and limitations under various experimental conditions. Robust clinical evidence indicates that organic anion transporting polypeptides (OATP) 1B1 and OATP1B3 play pivotal roles in the hepatic uptake of numerous anionic drugs. Yoshikado, et al. aims to compare the differences between PHH and SHH in determining hepatic clearance for several OATP1B substrate drugs.

They determined and compared the kinetic parameters of different batches of PHH amd SHH. Substrates including DHP and SC-62807 for OATP1B were also analyzed for rat and human liver distribution by positron-emission tomography. The PS_inf (influx intrinsic clearance through the sinusoidal membrane) values for CRV, PTV, and RSV were similar between PHH and SHH, but PRV, DHP, and SC-62807 showed 5- to 10-fold lower values in PHH compared to SHH (Fig. 1A). The concentration-to-medium (C/M) ratios at 37°C for the high uptake compounds (CRV, PTV, RSV) were 3-5 times higher in PHH than SHH (Fig. 1B), whereas the low uptake compounds (PRV, DHP) exhibited roughly half the values in PHH compared to SHH. The f_T (unbound fraction in hepatocytes) values were mostly comparable between both cell types (Fig. 1C). The K_p,uu (cell-to-medium unbound concentration ratio) values were higher in PHH than SHH, with fold differences as follows: 1.9 for DHP, 2.7 to 4.4 for PRV, PTV, SC-62807, and CRV, and 13 for RSV (Fig. 1D). The interlot differences assessed by the coefficient of variation (CV) were modest for hepatic uptake clearance of PTV and RSV regardless of the use of PHH and SHH. Hydrophilic compounds like SC-62807, PRV, and DHP showed low initial uptake in PHH with higher CV values than in SHH, possibly due to drug wash-off effects. Conversely, the hydrophobic CRV displayed higher CV values in SHH than PHH, likely reflecting variable non-specific adsorption to the cell surface.

Fig. 1. Comparison of kinetic parameters for six compounds obtained using PHHs and SHHs (Yoshikado, T., Lee, W., et al., 2020).

A Novel Unified Approach to Predict Human Hepatic Clearance for Both Enzyme- and Transporter-Mediated Mechanisms Using Suspended Human Hepatocytes

Riccardi, et al. introduce a novel method using suspended human hepatocytes to predict human hepatic clearance for compounds, which may be substrates of drug-metabolizing enzymes and/or transporters.

Riccardi, et al. examine 32 structurally diverse compounds, covering five ECCS classes (1a, 1b, 2, 3b, 4). It summarizes the physicochemical and in vitro data for compounds unlikely to have biliary excretion (ECCS 1a, 1b, and 2) and those with potential significant biliary excretion (ECCS 3b and 4). For compounds without significant biliary excretion (19 compounds), the novel extended clearance method (Method I) showed good IVIVE results, with most compounds (16 out of 19) having predicted values within threefold of observed values. Outliers included pitavastatin, telmisartan, and theophylline. Conversely, the traditional method (Method II), which considers only metabolic clearance, systematically underpredicted hepatic clearance, with only 26% of predictions within threefold of observed values, indicating that transporter-mediated clearance is also important. Similar trends were observed in predicting hepatic intrinsic clearance. The AFE for hepatic clearance using Method I and II were 1.9 and 4.1, respectively, and the bias values were 0.84 and 0.30, indicating Method I's higher accuracy (Fig. 2). For compounds with potential significant biliary excretion (13 compounds), 38% of predictions using Method I were within threefold, compared to 23% using Method II. Intrinsic clearance was also underpredicted (Fig. 3). AFE and bias values confirmed that Method I is more reliable for these compounds.

Fig. 2. Observed and predicted clearance for compounds without the potential for biliary excretion as a major clearance pathway (Riccardi, K. A., Tess, D. A., et al., 2019).

Fig. 3. Observed and predicted clearances for compounds with the potential for biliary excretion as a major clearance pathway (Riccardi, K. A., Tess, D. A., et al., 2019).