Investigations into the liver effects of ximelagatran using high content screening of primary human hepatocyte cultures

Background: Ximelagatran, the first oral agent in the new class of direct Thrombin inhibitors, was withdrawn from the market due to increased rates of liver enzyme elevations in long-term treatments. Despite intensive pre clinical investigations the cellular mechanisms behind the observed hepatic effects remain unknown.

Objective: The aim of this study was to assess drug-induced cytotoxicity in primary human hepatocyte cultures by ximelagatran and Other reference pharmaceutical agents with known in vivo hepatotoxic profiles.

Methods: Drugs cause liver injury by many distinct mechanisms that result in abnormal cellular functioning and different patterns of injury. To address many potential toxic mechanisms in a human-relevant model, freshly isolated human hepatocytes were used in automated imaging assays. Ximelagatran was used as a test compound to study biochemical and morphological changes in human hepatocytes. In addition, 11 control, reference and comparator compounds with known liver-toxic potential in humans were used. The response to these compounds was assessed across five different hepatocyte donor preparations.

Results: Cytotoxicity induced by a number of compounds was quantitatively monitored using an automated imaging technique. A variety of morphological changes in hepatocyte Cytoskeleton and mitochondrial function could be identified at sublethal doses of test compounds. Doses of ximelagatran up to 500 microM did not cause a cytotoxic response in the majority of preparations and no subcytotoxic response was observed at doses below 125 microM.

Conclusions: The experiments described here demonstrate that primary human hepatocytes may be used in a medium-throughput format for screening using imaging-based assays for the identification of cellular responses. Overall, it is concluded that ximelagatran did not cause a significant decrease in cell viability when incubated for 24 h at considerably higher concentrations than are found in plasma following therapeutic dosing.