Mechanistic Modeling with Dilisym® Predicts Species Differences in CKA Via Multiple Hepatotoxicity Mechanisms
Objective: To predict species differences in CKA-mediated hepatotoxicity using DILIsym®, a mechanistic model of druginduced liver injury (DILI)
Methods: Inhibitory effects of CKA on bile acid (BA) and bilirubin transporters were assessed using transporteroverexpressing vesicles and cells. CKA-mediated oxidative stress and mitochondrial dysfunction were determined in HepG2 cells. These in vitro data were used to define hepatotoxicity parameters and combined with PBPK sub-model simulations of hepatic compound exposure to predict DILI in DILIsym. Previously constructed human and rat simulated populations (SimPopsTM) that incorporate variability in the aforementioned toxicity mechanisms were utilized to determine the impact of inter-individual variability upon administration of single CKA doses of 900mg and 500mg/kg, respectively.
Results: CKA induces oxidative stress (oxidative stress production rate constant=7278mL/mol/hr human, 9705 mL/mol/hr rat) and inhibits mitochondrial electron transport chain (ETC) flux (ETC inhibition coefficient=14.2 mM human, 1.42 mM rat). CKA inhibits human BSEP (IC50=129.7 μM), rat
Bsep (IC50=94 μM), human MRP3 (IC50=11.2 μM), human NTCP (IC50=19.5 μM), rat Mrp2 (IC50=68.5 μM), and human OATP (IC50=0.84 μM). CKA was modeled as a noncompetitive inhibitor of BSEP/Bsep and MRP3/Mrp3 and a competitive inhibitor of NTCP/Ntcp. Due to lack of data, IC50 values for NTCP/Ntcp, MRP3/Mrp3, MRP2/Mrp2, and OATP/Oatp were assumed the same across species. Human SimPops predicted modest increases <1.5x upper limit of normal (ULN) in serum ALT, recapitulating the clinical data. Rat SimPops predicted ALT elevations >3xULN in 36.4% of the population, slightly underpredicting the 75% observed in preclinical trials. DILIsym recapitulated preclinical observations in bilirubin increase due to both DILI and bilirubin transporter inhibition. Rat SimPops predicted increases in total bilirubin >2xULN for 100% of the population, mirroring preclinical data. Conversely, no significant increases in bilirubin were observed in human SimPops, consistent with clinical observations.
Conclusion: Using in vitro data to determine toxicity parameters, DILIsym accurately predicted CKA hepatotoxicity in rats and not in humans, consistent with observed preclinical and clinical data.
Seventh American Conference on Pharmacometrics (ACoP), October 22-28, 2016, Bellevue, Washington
By Christina Battista, Kyunghee Yang, Jerome Mettetal, Simone Stahl, Paul Watkins, Brett Howell, Scott Siler