How useful are clinical liver function tests in in vitro human hepatotoxicity assays?

In preclinical hepatotoxicity testing cell based assays are frequently employed. However, prediction of clinical drug induced liver injury (DILI) remains a major challenge. Here we examined the usefulness of frequently employed markers of hepatocellular injury in cultures of primary human hepatocytes (PHH) in response to treatment with either paracetamol, rifampicin, petadolex and/or amiodarone. The changes in the metabolic competency (urea and albumin) and cellular injury (AST, ALT, ALP, LDH, γGT and succinate dehydrogenase) were determined at therapeutic and above drug concentrations as to evaluate the utility of these markers in in vitro systems. Initially, treatment of PHH with any of the drugs caused a statistically significant reduction in enzyme activities to suggest a switch from basic amino acid metabolism towards induced detoxification. However, treatment for prolonged periods of time caused cytolysis, as evidenced by the significant rise in extracellular LDH and the concomitant increase in ALT and AST activity. Notably, amongst the various endpoints studied, urea was best to demonstrate dose dependent metabolic stress, while other markers of hepatocellular injury were highly variable. Taken collectively, urea measurement proofed to be robust in predicting hepatocellular stress; therefore it should be included in preclinical testing strategies for an improved prediction of DILI.