Medicine
Genomic Markers of Drug-Induced Liver Injury Susceptibility
Quick fact
Specific variants of the HLA class I and class II genes are strongly associated with DILI from common drugs; for example, HLA-B57:01 is linked to a 7-fold increased risk of flucloxacillin-induced liver injury, yet this variant is present in fewer than 5% of the population.
Why this is interesting
Every year, seemingly safe drugs—like antibiotics or painkillers—cause severe liver failure in a few patients. Why does one person's liver tolerate a drug while another's fails catastrophically?
Read the full explanation
Understanding Genomic Markers of Drug-Induced Liver Injury Susceptibility
Drug-induced liver injury (DILI) is a complex adverse reaction that can occur with many medications. While it appears unpredictable, part of the risk is inherited through our DNA. Our cells need to process foreign compounds (drugs) and then eliminate them. This process involves enzymes (like those in the CYP450 family) that often turn a drug into a reactive intermediate—which can be harmless or toxic. The toxic intermediate can either directly damage liver cells or trigger an immune reaction. The immune system, via molecules called HLA (human leukocyte antigens), displays fragments of the drug or its modified proteins on the surface of liver cells to T cells. If a person carries a particular HLA variant, the drug fragment fits better in the 'grip' of the HLA molecule, causing a misguided immune attack on liver cells. This explains why only a minority develop DILI—they have a 'self-defense' system that misidentifies a drug as a threat. In addition, transporters like the bile salt export pump (BSEP) can be blocked, leading to bile buildup and toxic effects.
A deeper explanation
The mechanistic basis of genomic susceptibility to DILI lies in two main pathways: direct metabolic toxicity and immune-mediated (idiosyncratic) reactions. Genetic variants in enzymes involved in drug metabolism—such as CYP2C9, CYP2D6, and UGTs—can lead to an imbalance between the production and detoxification of reactive metabolites. If detoxification pathways (e.g., glutathione conjugation) are less active, toxic intermediates accumulate and damage mitochondria or cell membranes. On the immune side, HLA genes encode proteins that present peptides to T cells. Drug-modified peptides can be presented in a 'foreign' manner, leading to a T-cell response. Only certain HLA molecules have the exact binding pocket to present these drug adducts effectively. For example, HLA-B57:01 is associated with flucloxacillin-induced cholestatic hepatitis, while HLA-DRB115:01 increases risk for co-amoxiclav injury. Genome-wide association studies have identified these and other loci, such as PTPN22, which modulate T-cell activation. Therefore, a person's genomic profile can be used to estimate their susceptibility to DILI. Understanding these markers is crucial for drug safety, personalized prescribing, and for stratifying patients in clinical trials.