Enhanced HepaRG Cells Improve Drug Metabolism & Toxicity Testing | PLOS ONE

Researchers have engineered a human liver cell model with significantly improved capacity to process certain medications, a development that could lead to more accurate prediction of drug-induced liver toxicity. The advance, detailed in a study published in PLOS ONE on December 29, 2025, centers on enhancing the activity of CYP2D6, a crucial enzyme involved in metabolizing a wide range of pharmaceuticals.

Understanding Drug Metabolism and the Role of CYP2D6

The liver is the body’s primary detoxification organ, and a key part of that process involves enzymes that break down drugs into forms that can be eliminated. These enzymes, particularly the cytochrome P450 (CYP) family, are responsible for metabolizing over 80% of clinically used drugs. Variations in CYP enzyme activity can significantly impact how individuals respond to medications – some people metabolize drugs quickly, requiring higher doses, while others metabolize them slowly, increasing the risk of side effects. Genetic variations, age, diet, and other medications can all influence CYP activity.

CYP2D6, specifically, is involved in the metabolism of approximately 25% of all drugs, including antidepressants, antipsychotics, and pain medications. Predicting how a drug will be metabolized by CYP2D6 is critical during drug development, but current methods often rely on animal models or liver samples from deceased donors, both of which have limitations. Animal models don’t always accurately reflect human metabolism, and human samples can be scarce and variable.

A Latest Human Hepatocyte Model

The research, led by Associate Professor Shinpei Yamaguchi and the late Professor Masako Tada of Toho University in Japan, along with colleagues from the Faculty of Pharmaceutical Sciences at Toho University, focused on improving the HepaRG cell line. HepaRG cells are a commonly used human liver cell model, but their CYP2D6 activity is often lower than that found in actual human livers. The team successfully developed a modified HepaRG cell line with markedly enhanced CYP2D6 activity. Toho University’s research brief details the development.

This engineered model offers a more human-relevant system for evaluating potential drug-induced liver toxicity specifically related to CYP2D6 metabolism. Drug-induced liver injury (DILI) is a significant concern in drug development and a leading cause of drug withdrawal from the market. Identifying potential liver toxicity early in the development process can save time, money, and, most importantly, protect patients.

How the Study Was Conducted and What It Shows

The researchers developed the CYP2D6-enhanced HepaRG cell line and then assessed its metabolic capacity by measuring its ability to process various drugs known to be metabolized by CYP2D6. The modified cells demonstrated significantly higher CYP2D6 activity compared to standard HepaRG cells. The study, published in PLOS ONE, details the methods used to enhance CYP2D6 expression and the subsequent functional assays performed to validate the improved metabolic capacity. Chizuka Obara, Yohei Iizaka, Akari Mine, Yojiro Anzai, Masako Tada, and Shinpei Yamaguchi are listed as authors on the PLOS ONE publication.

It’s significant to note that this model focuses specifically on CYP2D6. Liver toxicity can be caused by many factors, and other CYP enzymes and metabolic pathways are also involved. The model doesn’t replicate the full complexity of the human liver, which includes a variety of cell types and interactions.

Broader Research Interests of Shinpei Yamaguchi

Associate Professor Shinpei Yamaguchi’s research extends beyond drug metabolism. His work, as detailed on his Google Scholar profile, encompasses epigenetics, developmental biology, germ cells, and genomic imprinting. He has also published research on parthenogenote-derived brain development and the role of paternal genomes in neural development. His research group at Toho University focuses on reprogramming and stem cell biology, with a particular interest in understanding the epigenetic mechanisms that regulate gene expression.

Implications for Drug Development and Patient Safety

This new hepatocyte model represents a step forward in improving the accuracy of drug safety testing. By providing a more human-relevant system for evaluating CYP2D6-mediated drug metabolism, it could support identify potential liver toxicity risks earlier in the drug development process. This could lead to the development of safer medications and more personalized drug therapies, taking into account individual differences in CYP2D6 activity.

What Comes Next: Refining the Model and Expanding Applications

The researchers are continuing to refine the HepaRG cell line and explore its potential applications in drug development. Future studies will likely focus on incorporating other relevant liver cell types and metabolic pathways to create a more comprehensive model of human liver function. Further research will also be needed to validate the model’s predictive power by comparing its results to clinical data from patients. The team is also investigating the potential of using this model to study drug-drug interactions and to identify biomarkers for drug-induced liver injury.