In support of this, a retrospective single-centre cohort study by Pascual-Oliver et al. involving IBD patients who received anti-TNF therapy as their first biologic treatment documented HLA-DQA1*05 status and found that carrying the HLA-DQA1*05 variant did not predict either primary or secondary response failure to anti-TNF treatment. This evidence concerns the gene HLA-DQA1 and inflammatory bowel disease.