Human leucocyte antigen class II genotype in susceptibility and resistance to co-amoxiclav-induced liver injury.

Background & Aims: Co-amoxiclav is one of the most common causes of drug-induced liver injury (DILI). Although there are previous reports of genetic associations between HLA class II and co-amoxiclav-related DILI, studies to date have been based on very small numbers from single centres only. In order to address this problem we have investigated the role of HLA class II DRB1 and DQB1 in 61 cases of co-amoxiclav DILI as part of a UK-wide multicentre study.

Methods: HLA alleles and genotypes were compared with those of 40 individuals exposed to co-amoxiclav without toxicity (treated controls) and 191 population controls.

Results: There were two significant findings from the study. First, HLA-DRB1*15 was increased in patients (53%) versus both treated (33%: OR=2.29: 95% CI: 1.00-5.26) and population controls (30%: OR=2.59:95% CI: 1.44-4.68: p=0.002). Second, DRB1*07 was found to be reduced in patients (9.8%) compared to both treated (35%: OR=0.18: 95% CI: 0.06-0.52: p=0.0011, pc=0.0154) and population controls (29%: OR=0.266: 95% CI: 0.11-0.65: p=0.0019, pc=0.0266).

Conclusions: These results confirm the previously reported significant genetic risk for HLA-DRB1*15 and also provide evidence of a protective effect of the HLA-DRB1*07 family of alleles. HLA alleles and haplotypes may be particularly important in susceptibility and resistance to co-amoxiclav-DILI, but it remains to be seen whether this effect is due to the identified alleles or others in close linkage disequilibrium elsewhere on the MHC.