Introduction:
One of the major causes of failure in the drug development process is related to safety concerns arising in clinical trials or drugs withdrawn during the postmarketing phase. Most frequently, hepatotoxicity represents the cause of such failure. Therefore providing a valuable tool that could predict liver toxicity in early stages of drug discovery could prevent failure in clinical trials avoiding waste of investment and time.
Goals:
In this study, we developed and validate an in vitro approach for hepatotoxicity prediction for its applicability in the initial phase of the drug discovery process. This approach is based on testing hepatocytes viability after acute and chronic exposure to commercial drugs.
Methods:
The cytotoxic effect induced by each compound was assessed by comparing the viability percentage of treated cells to the viability percentage of untreated cells. Cells viability was established detecting the level of ATP released by the cells, as a measure of metabolically active, thus alive cells. In every test, results were expressed as lethal concentration 50 (LC50). We tested the compounds to the human hepatocytes HepaRG, rat and pig primary hepatocytes, as rodent and non-rodent animal models, respectively. Cells were cultured in 2D configurations (monolayer and sandwich) and 3D (spheroids).
Results:
We exposed a set of commercial compounds, with different known liver toxicity profile, in three different in vitro models: monolayer, sandwich culture and 3D spheroids of human HepaRG, rat and pig primary hepatocytes. We found that spheroids were the most sensitive and responsive model to drug-induced liver injury, while monolayer and sandwich culture showed lower sensitivity. Furthermore, we observed significant differences in the hepatotoxic responses of different species, indicating that neither rodent nor non-rodent models can accurately predict human liver toxicity. Our results suggest that spheroids of human HepaRG hepatocytes are the most suitable in vitro model for screening new compounds for hepatotoxicity in the initial phase of drug discovery.