This observational study aims to identify genes that may affect how patients with inflammatory bowel disease respond to anti-TNF treatment and why some patients lose response to treatment over time. The study will examine whether genetic markers can help predict which patients are more likely to respond to anti-TNF therapy.

Participants who have not previously received anti-TNF treatment and are about to start advanced therapy will provide a blood sample to test for the genetic markers. Participants will also undergo regular assessments of current treatment, disease activity, and inflammatory markers during follow-up.

The introduction of anti-TNF therapy was a pivotal milestone in the treatment of inflammatory bowel diseases (IBD). Since then, additional advanced therapies with novel mechanisms of action have been introduced. The plethora of biologics and small molecule drugs increases the ability of IBD patients to achieve therapeutic goals, such as clinical, endoscopic and mucosal healing. However, primary non-response and loss of response remain a challenge and are linked to increase risks related to ongoing inflammation and disease progression.

Predicting the response rates of individual patients to therapy is the goal of a large body of research, linked to clinical characteristics, genetics, microbiome composition and pharmacokinetics. Two promising research topics are Triggering Receptor Expressed in Myeloid cells 1 (TREM1) and HLA-DQA1*05.

TREM1 is a receptor expressed on innate immune cells, known to amplify inflammatory signals triggered by Toll-like receptors, thus contributing to the pathophysiology of acute and chronic inflammatory conditions. Increased protein and mRNA levels of TREM1 in whole blood and colonic biopsies are associated with clinical and endoscopic non-response to anti-TNF. The suggested best cut-off point is 3.346 folds increase in mRNA expression in whole blood samples, with a specificity of 91.3% and sensitivity of 58.1%.

HLA class II gene HLA-DQA1 is expressed by antigen presenting cells and encodes the α-chain of the HLA-DQ heterodimer that forms part of the antigen-binding site where epitopes are presented to T-helper cells. Carriage of HLA-DQA1*05 allele confers a 2-fold risk of immunogenicity to anti-TNF therapy. This risk was mitigated using a concomitant immunomodulator.

Our goal is to evaluate the predictive power of these tests separately in a prospective observational study, and assess whether combining the tests' outcomes prior to initiation of anti-TNF therapy improve therapy outcomes, including efficacy and durability.

The aims of this study are to assess the effectiveness of each test, and the combined tests for TREM1 and HLA-DQA1*05 to improve clinical and endoscopic response and remission rates, in patients with IBD starting anti-TNF therapy. The study will also assess the effectiveness of each test, and the combined tests for TREM1 and HLA-DQA1*05 in improving anti-TNF treatment durability and immunogenicity.

Participants will provide blood samples prior to treatment initiation for the assessment of HLA-DQA1*05 using quantitative real-time polymerase chain reaction (qRT-PCR) and TREM1 levels using an enzyme-linked immunosorbent assay (ELISA).

Drug and antibody levels will be measured at weeks 8, 24, and 52. Participants will also undergo periodic evaluations of their medical therapy and clinical disease activity throughout the study period.

Endoscopic disease activity (endoscopic MAYO score [eMAYO] for UC, and simple endoscopic score [SES-CD] for CD) will be evaluated with endoscopy 6-12 months after starting therapy, if performed as standard of care by the treating physician's discretion.

Statistical analysis Continuous variables will be presented as mean ± standard deviation for normal distribution and median with interquartile range for non-normal distribution. Nominal variables will be presented as proportions. Pearson correlation coefficient will be calculated to find association between HLA-DQA1*05 and anti-TNF immunogenicity, and between TREM1 expression and anti-TNF response rates. ROC curve with Youden index will be used to calculated area under the curve and optimal tests results predicting immunogenicity and response to therapy. Chi-Square test will be used to test the association between nominal variables. Comparison of continued variables groups will be performed by the independent samples t-test for variables which distribute normally, and by the Mann-Whitney test for variables which did not distribute normally. Normality will be tested graphically and using the Shapiro Wilk's test. Comparison of immunogenicity and response to therapy between study visits, and evaluation of the overtime trends in these parameters, in accordance with HLA-DQA1*05 and TREM1 tests results, will be performed by using the linear mixed model analysis (three or more visits) and by the paired sample T test (two visits). Statistical significance was set at P ≤ 0.05. All statistical analyses will be performed using R-4.3.2 for Windows.

Inclusion Criteria:

• Established IBD: Crohn's disease (CD) or ulcerative colitis (UC)
• Anti-TNF naïve
• Clinically active disease (HBI>5 for CD, p-MS≥ 3 for UC)
• Elevated inflammatory indices CRP>10 or fecal calprotectin>250

Exclusion Criteria:

• Unable to provide informed consent
• Anti-TNF experienced
• Unable to complete the study protocol

Patients followed in the IBD unit in TLVMC starting or switching biologic therapy

At this time, there are no plans for data sharing or external collaborations. If data sharing is pursued in the future; only de-identified participant data will be shared, including demographic information, clinical indices and response to treatment.