Related Experiment Video
Updated: May 29, 2026
Human Liver Microphysiological System for Assessing Drug-Induced Liver Toxicity In Vitro
Published on: January 31, 2022
Metabolic activation in drug-induced liver injury
Louis Leung1, Amit S Kalgutkar, R Scott Obach
1Pharmacokinetics, Dynamics, and Metabolism Department, Pfizer Global Research and Development, Groton, Connecticut 06340-5196, USA. louis.leung@pfizer.com
Abstract:
It is generally believed that metabolic bioactivation of drug molecules to form reactive metabolites, followed by their covalent binding to endogenous macromolecules, is one of the mechanisms that can lead to hepatotoxicity or idiosyncratic adverse drug reactions (IADRs). Although the role of bioactivation in drug-induced liver injury has been reasonably well established and accepted, and methodologies (e.g., structural alerts, reactive metabolite trapping, and covalent binding) continue to emerge in an attempt to detect the occurrence of bioactivation, the challenge remains to accurately predict the likelihood for idiosyncratic liver toxicity. Recent advances in risk-assessment methodologies, such as by the estimate of total body burden of covalent binding or by zone classification, taking the clinical dose into consideration, are positive steps toward improving risk assessment. The ability to better predict the potential of a drug candidate to cause IADRs will further be dependent upon a better understanding of the pathophysiological mechanisms of such reactions. Until a thorough understanding of the relationship between liver toxicity and the formation of reactive metabolites is achieved, it appears, at present, that the most practical strategy in drug discovery and development to reduce the likelihood of idiosyncratic liver toxicity via metabolic activation is to minimize or eliminate the occurrence of bioactivation and, at the same time, to maximize the pharmacological potency (to minimze the clinical dose) of the drug of interest.
Insights
Drug bioactivation can cause liver damage. Minimizing reactive metabolites and maximizing drug potency are key strategies to reduce the risk of idiosyncratic liver toxicity during drug development.
Area of Science:
- Drug metabolism and toxicology
- Pharmacology
- Medicinal chemistry
Background:
- Metabolic bioactivation of drugs to reactive metabolites, followed by covalent binding to macromolecules, is a known cause of drug-induced liver injury and idiosyncratic adverse drug reactions (IADRs).
- While the role of bioactivation in liver toxicity is accepted, accurately predicting the likelihood of idiosyncratic liver toxicity remains a challenge.
- Emerging methodologies like structural alerts, reactive metabolite trapping, and covalent binding assays aim to detect bioactivation events.
Purpose of the Study:
- To review the current understanding of metabolic bioactivation in drug-induced liver toxicity.
- To discuss the challenges and recent advances in predicting idiosyncratic liver toxicity.
- To propose practical strategies for mitigating liver toxicity risks in drug discovery and development.
Main Methods:
- Literature review of metabolic bioactivation pathways and their link to hepatotoxicity.
- Analysis of current methodologies for detecting reactive metabolites and covalent binding.
- Evaluation of recent risk-assessment strategies, including total body burden and zone classification, considering clinical dose.
Main Results:
- Advances in risk assessment, such as estimating covalent binding burden and zone classification with dose consideration, represent progress.
- A deeper understanding of the pathophysiological mechanisms of IADRs is crucial for improved prediction.
- Minimizing bioactivation and maximizing pharmacological potency to reduce clinical dose are currently the most practical approaches.
Conclusions:
- Reducing the occurrence of bioactivation and increasing drug potency are essential strategies to minimize idiosyncratic liver toxicity.
- Further research into the relationship between liver toxicity and reactive metabolite formation is needed.
- Accurate prediction of IADRs requires a comprehensive understanding of underlying mechanisms and improved risk assessment tools.
Related Concept Videos
01:14Effect of Hepatic Disease on Pharmacokinetics: Active Drug, Metabolite and Fraction of Metabolized Drug
01:22Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test
01:25Bioactivation and Tissue Toxicity
01:26Effect of Hepatic Disease on Pharmacokinetics: Drug Dosing and Hepatic Blood Flow
01:17Drug Metabolism: Phase I Reactions
01:16Drug Biotransformation: Overview