It is estimated that 90% of all compounds entering clinical trials fail, largely due to safety issues in clinical phases or drug efficacy issues in patients. This failure is because preclinical approaches that use in vivo animal models and in vitro cell models for discovery and development do not reliably translate to patients. Just as preclinical animal models fail to predict human liver safety accurately, the current in vitro cellular models fail, too. The application of in vitro safety studies has not changed significantly in decades. Using overly simplistic, two-dimensional (2D) in vitro liver cell culture models—from cell lines or primary human hepatocytes (PHH)—as a filter for liver toxicity screening in frontloaded assays has only limited value.

In this webinar, Dr. Wolf will present novel in vitro models and methodologies for studying drug-induced liver injury (DILI). At the foundation of his recommended approach are 3D liver microtissues (also known as spheroids), the smallest functional unit of the liver. Produced from human primary liver cells under scaffold-free aggregation conditions and recapitulate structures and functionality similar to native liver, these microtissues comprise hepatocytes, Kupffer cells, and liver endothelial cells. They can be used for investigating a broad range of experimental conditions by various analytical methods, from liver enzyme markers and histological techniques to the latest omics technologies. One critical feature is the longevity and stability of these human liver co-cultures, which are viable for up to 28 days in culture. This enables multiple daily treatment at therapeutic concentrations similar to those used in the clinic.

Major applications of human 3D microtissues are hazard identification in the early discovery phase and in mechanistic investigative toxicology. If DILI is observed in preclinical animal models, “cross species” animal liver microtissues can be used to recapitulate observed in vivo effects by mechanistic studies in vitro. At the level of 3D microtissues experiments, translation to human patients can be improved.

A novel experimental approach for identifying human DILI mechanisms is the “causality assay” framework. With this method, a specific pathway modulator (either an enhancer/agonist or inhibitor/antagonist) is co-incubated with the DILI compound. Examples of enhancers include BSO (inhibitor of GSH synthesis), LPS (inflammation), bile acids, etc. Inhibitors may include antioxidants (ROS), specific enzymatic inhibitors, gene silencing or knock-outs, amongst others. The choice of modulator can result in shifting the IC50 cytotoxicity curve, indicating a causal link between the pathway modulation and the cellular response.

Dr. Wolf will show examples of successful applications of causality assays for the deconvolution of major DILI mechanisms—and offer a vision for the future of 3D in vitro tools for translational liver toxicology.