Cytotoxic Reactive Metabolite Assay with Permeabilized Cryopreserved Human Hepatocytes for the Identification of Drug Candidates With Potential to Cause Idiosyncratic Drug-induced Liver Injuries
By: Hong (Ivy) Wei and Albert P. Li, Discovery Life Sciences, Columbia, MD and Malden, MA
- Drug induced liver injuries (DILI) resulting in deaths or a need for liver transplantation of marketed drugs is a major challenge in drug development.
- A large majority of DILI drugs are known to be metabolized to highly reactive metabolites which, because of covalent binding to key biological molecules, may lead to a cascade of events ultimately resulting in severe liver toxicity.
- Current experimental approaches in drug development for the identification drug candidates with potential to form reactive metabolite involve the incubation of the drug candidates with human liver microsomes in the presence of a trapping agent such as glutathione, followed by LCMS/ MS identification of the reactive metabolite-GSH conjugates as well as quantification of covalent binding to human liver microsomal proteins.
- While it is generally believed that early identification of chemical structures prone to reactive metabolite formation for the selection of chemical structures and direction of structural modification may minimize toxic liability in drug discovery, there are concerns with the possibility of inadvertent removal of drug candidates without toxicological consequences with this approach.
- We present here a novel experimental assay, the Metabolism- Dependent Cytotoxicity Assay (MDCA) to identify reactive metabolites with toxicological consequences, therefore allowing a more accurate identification of structures with toxic liability.