HLA DQA1*05 and risk of anti-TNF treatment failure and anti-drug antibody development in children with Crohn's Disease: HLA DQA1*05 and Pediatric Crohn's Disease

Objectives:HLA DQA1*05 has been associated with the development of anti-drug antibodies (ADA) to tumor necrosis factor antagonists (anti-TNF) and treatment failure among adults with Crohn's disease (CD). However, findings from other studies have been inconsistent with limited pediatric data.Methods:We analyzed banked serum from patients with CD < 21 years of age enrolled in COMBINE, a multi-center, prospective randomized trial of anti-TNF monotherapy vs. combination with methotrexate. The primary outcome was a composite of factors indicative of treatment failure. The secondary outcome was ADA development.Results:A trend towards increased treatment failure among HLA DQA1*05 positive participants was not significant (HR 1.58, 95% CI 0.95-2.62; p=0.08). After stratification by HLA DQA1*05 and by methotrexate vs. placebo, patients who were HLA DQA1*05 negative and assigned to methotrexate experienced less treatment failures than HLA DQA1*05 positive patients on placebo (HR 0.31, 95% CI 0.13-0.70; p=0.005).A trend toward increased ADA development among HLA DQA1*05 positive participants was not significant (odds ratio [OR] 1.96, 95% CI 0.90-4.31, p=0.09). After further stratification, HLA DQA1*05 negative participants assigned to methotrexate were less likely to develop ADA relative to HLA DQA1*05 positive patients on placebo (OR 0.12, 95% CI 0.03-0.55; p=0.008).Conclusions:In a randomized trial of children with CD initiating anti-TNF, 40% were HLA DQ-A1*05 positive, which was associated with a trend toward increased risk of both treatment failure and ADA. These risks were mitigated, but not eliminated, by adding oral methotrexate. HLA DQ-A1*05 is an important biomarker for prognosis and risk stratification.