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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., (Copyright © 2024 by The American College of Gastroenterology.)

Background: Higher drug levels and combination therapy with low-dose oral methotrexate (LD-MTX) may reduce anti-tumor necrosis factor (TNF) treatment failure in pediatric Crohn's disease. We sought to (1) evaluate whether combination therapy with LD-MTX was associated with higher anti-TNF levels, (2) evaluate associations between anti-TNF levels and subsequent treatment failure, and (3) explore the effect of combination therapy on maintenance of remission among patients with therapeutic drug levels (>5 µg/mL for infliximab and >7.5 µg/mL for adalimumab)., Methods: We conducted a post hoc analysis of the COMBINE trial, which compared anti-TNF monotherapy to combination therapy with LD-MTX. We included participants who entered maintenance therapy and provided a serum sample approximately 4 months from randomization., Results: Among 112 infliximab and 41 adalimumab initiators, median drug levels were similar between combination therapy and monotherapy (infliximab: 8.8 vs 7.5 μg/mL [P = .49]; adalimumab: 11.1 vs 10.5 μg/mL [P = .11]). Median drug levels were lower in patients experiencing treatment failure (infliximab: 4.2 vs 9.6 μg/mL [P < .01]; adalimumab: 9.1 vs 12.3 μg/mL [P < .01]). Among patients treated with infliximab with therapeutic drug levels, we observed no difference in treatment failure between participants assigned monotherapy or combination therapy. Among patients treated with adalimumab, a trend towards reduced treatment failure in the combination therapy arm was not statistically significant (P = .14)., Conclusions: LD-MTX combination was not associated with higher drug levels, but higher drug levels were associated with reduced risk of treatment failure. Among patients with therapeutic drug levels, we observed no benefit of LD-MTX for patients treated with infliximab. A nonsignificant trend towards reduced treatment failure with the addition of LD-MTX patients treated with adalimumab warrants further investigation., (© The Author(s) 2024. Published by Oxford University Press on behalf of Crohn’s & Colitis Foundation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)