Liver safety evaluation of endothelin receptor antagonists using HepatoPac®: A single model impact assessment on hepatocellular health, function and bile acid disposition

• Published in: Journal of applied toxicology Vol. 39; no. 8; pp. 1192 - 1207
• Main Authors: Aleo, Michael D., Ukairo, Okechukwu, Moore, Amanda, Irrechukwu, Onyi, Potter, David M., Schneider, Richard P.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.08.2019
• Subjects: Adenosine triphosphate; ambrisentan; Amiodarone; ATP; Bile; Biocompatibility; bosentan; Cell culture; Cellular manufacture; CI‐1034 (fandosentan); Clinical trials; Dogs; Drug metabolism; Drugs; drug‐induced liver injury (DILI); endothelin receptor antagonists (ETRAs); Endothelins; Excretion; Glutathione; Health risks; hepatocyte micropatterned co‐cultures (MPCCs); hepatopac; Human populations; In vivo methods and tests; Injuries; Liver; Medical research; Pharmaceuticals; Populations; Predictions; Safety; Secretion; sitaxsentan; Taurocholic acid; Toxicants; Toxicity; Transaminase; Transport; Urea; endothelin receptor antagonists (ETRAs); hepatopac; hepatocyte micropatterned co-cultures (MPCCs); CI-1034 (fandosentan); bosentan; ambrisentan; sitaxsentan; drug-induced liver injury (DILI)
• ISSN: 0260-437X; 1099-1263
• DOI: 10.1002/jat.3805

Marketed (bosentan, ambrisentan) and discontinued (sitaxsentan, CI‐1034) endothelin receptor antagonists were examined in the human micropatterned hepatocyte co‐culture (MPCC) model HepatoPac®. Differences across hepatocellular health (cellular adenosine triphosphate/glutathione content), function (urea production/albumin secretion) and taurocholic acid transport (biliary clearance/excretion index) were compared using amiodarone and ciclosporin A as positive controls. Ambrisentan had the weakest potency in all six endpoints, while sitaxsentan, bosentan and CI‐1034 had more potent effects on hepatobiliary transport than health/function endpoints. Normalization to clinical Cmax gave the following relative rank order of safety based on margins for each endpoint: ambrisentan ≥ CI‐1034 ~ bosentan > sitaxsentan. These data suggested impaired hepatobiliary disposition might contribute to a more prominent role in liver injury associated within sensitive human populations exposed to these compounds than direct hepatocellular toxicity. Rat, dog and monkey MPCCs also showed greater sensitivity potential to disrupted hepatobiliary disposition compared with hepatocellular health/functional endpoints. Drug metabolism competency was exhibited across all species. In vivo, rats and dogs appear more resistant to transaminase elevations and/or histological evidence of liver injury caused by these mechanisms even at exceedingly high systemic exposures relative to sensitive humans. Rats and dogs are resistant to hepatobiliary toxicants due to physiological differences in bile composition/handling. Although traditional animal testing provides adequate safety coverage for advancement of novel pharmaceuticals into clinical trials, supplemental assays employing human MPCCs may strengthen weight‐of‐evidence predictions for sensitive human populations. Proving the predictive value of this single impact assessment model in advance of clinical trial information for human liver injury risk is needed across more pharmaceuticals. Endothelin receptor antagonists were examined in the human micropatterned hepatocyte co‐culture model HepatoPac®. Rank order of safety was ambrisentan ≥ CI‐1034 ~ bosentan > sitaxsentan using a weight‐of‐evidence approach based on endpoint normalization to clinical Cmax. Hepatocellular transport effects were sensitive endpoints compared with function/viability. Rat, dog and monkey hepatocytes displayed similar effects. Animal toxicology studies demonstrated evidence of impaired biliary transport, but only at high exposures. Hepatobiliary transport dysfunction may play a role in liver injury with these compounds more than overt hepatocellular toxicity.