P607 HLA-DQA1*05 Allele Carriage and Anti-TNF Therapy Persistence in Inflammatory Bowel Disease

Abstract Background Carriage of HLA-DQA1*05 allele is associated with development of antidrug antibodies (ADA) in patients with Crohn’s Disease (CD) receiving anti-TNF therapy. The presence of ADA is not uniformly associated with anti-TNF therapy failure as patients with adequate trough drug concentrations, even where ADA are present, can maintain therapy response. We aimed to determine the impact of carriage of HLA-DQA1*05 allele on outcome of anti-TNF therapy evaluated by drug persistence in routine clinical practice. Methods A multi-centre retrospective study of IBD patients treated with anti-TNF therapy was performed. HLA-DQA1*05 genotypes were generated for each included patient by imputation from whole genome sequence using HIBAG. Only outcome of first anti-TNF therapy received by patients was evaluated in this study. Study primary endpoint was anti-TNF therapy persistence, expressed as time to discontinuation of anti-TNF therapy, segregated by HLA-DQA1*05 allele genotype. Patients discontinuing anti-TNF therapy due to primary or secondary loss of response or due to side-effects were considered therapy failures. Statistical analysis was performed using survival analysis and multivariate cox logistic regression with effect of covariates on outcome expressed as odds ratios (OR). Results 921 IBD patients were identified with 877 included in the study population. Baseline demographics for the entire cohort and segregated by HLA-DQA1*05 allele status are summarised in Figure 1. In the study population, 543 (62%) had no copy, 281 (32%) one copy and 53 (6%) two copies of HLA-DQA1*05 allele. Median time to anti-TNF therapy discontinuation in patients with 2 copies of HLA-DQA1*05 allele was significantly shorter compared to patients with 1 or no copy at 700-days follow-up: 418 versus 513 versus 541 days respectively, p=0.007 (Figure 2) with similar results observed at 2000-days follow-up (p=0.04). In a multivariate regression, factors independently associated with time to anti-TNF therapy discontinuation included: carriage of HLA-DQA1*05 allele OR 1.2, p=0.02; male gender OR 1.6, p=4.2 x 10-5; CD phenotype OR 0.7, p=0.009; and anti-TNF therapy type (infliximab) OR 1.5, p=0.002. Concomitant immunomodulator use was not associated with time to anti-TNF therapy discontinuation in this model, OR 0.97, p=0.84. Conclusion Carriage of two HLA-DQA1*05 alleles is associated with a less favorable outcome of anti-TNF therapy with shorter time to therapy discontinuation. Carriage of one HLA-DQA1*05 allele is not associated with outcome of anti-TNF therapy. Assessing HLA-DQA1*05 genotype has value in routine clinical practice as HLA-DQA1*05 homozygotes are at increased risk of anti-TNF failure which should be a consideration in IBD therapy selection.