Evaluation of Infliximab Therapy in Children with Crohn's Disease Using Trough Levels Predictors.

BACKGROUND: In adults, infliximab (IFX) levels correlate with disease activity, and antibodies to IFX (ATIs) predict treatment failure. We aimed to determine the association of IFX levels and ATIs with disease activity in a paediatric population. We prospectively collected blood, stool, and clinical data from 65 patients (age 10.5-15.1 years) with Crohn's disease (CD) before IFX administration, and measured IFX trough levels, ATIs, and faecal calprotectin levels (CPT). Samples were collected during maintenance therapy. We used multivariate analysis to identify the predictors of IFX levels. SUMMARY: Lower levels of IFX were associated with ATIs positivity (OR 0.027, 95% CI 0.009-0.077). Higher C-reactive protein (CRP) level, erythrocyte sedimentation rate, and CPT levels were found in patients with lower IFX levels. The optimal combination of sensitivity (0.5) and specificity (0.74) for disease activity was calculated for IFX levels ≥1.1 µg/mL using CRP level <5 mg/L as a marker of laboratory remission. In a model that used CPT ≤100 µg/g as the definition of remission, the optimal IFX trough level was 3.5 µg/mL. No independent association between remission and ATIs was found in our study population. However, we found an independentz association between IFX levels and serum albumin levels (OR 1.364, 95% CI 1.169-1.593), p < 0.001. Key Messages: The paediatric population was similar to adult populations in terms of the association between IFX and ATIs as well as between IFX and disease activity.

Association of Induction Infliximab Levels With Clinical Response in Perianal Crohn's Disease.

BACKGROUND: The association of infliximab [IFX] trough levels with clinical and endoscopic outcomes in inflammatory bowel disease is well established. However, there is scarce data regarding the association of perianal fistula response with IFX. The aim of this study was to establish whether early induction infliximab levels and anti-infliximab antibodies [ATIs] are associated with perianal fistula response. METHODS: Consecutive CD patients with perianal fistulae that were treated with IFX between 2008 and 2016 were included in the study. Response was defined as cessation or significant improvement of fistula drainage. Patients with unavailable IFX level or ATI measurements and/or missing clinical follow-up at Week 14 were excluded. RESULTS: A total of 36 patients with perianal fistulae were included; 25/36 [69.4%] responded to treatment by Week 14. The median induction IFX levels at Weeks 2, 6 and 14 in the responders group at Week 14 were higher compared with those of the non-responders group [20/5.6 µg/mL, P = 0.0001; 13.3/2.55 µg/mL P = 0.0001; 4.1/0.14 µg/mL, P = 0.01]. On multivariate analysis, IFX leve at Weeks 2 and 6 were significantly associated with fistula response at Weeks 14 and 30. IFX drug levels of 9.25 µg/mL at Week 2 and 7.25 µg/mL at Week 6 were the best predictors of fistula response. CONCLUSION: High IFX trough levels during induction are associated with favorable fistula response to anti-TNF treatment. If validated in a larger prospective study, our findings may help guide anti-TNF treatment in patients with perianal CD, and suggest serum level-guided treatment escalation in non-responders or prompt changing of biologic treatment in non-responders.

Therapeutic Drug Monitoring in Children and Young Adults With Inflammatory Bowel Disease: A Practical Approach.

Therapeutic drug monitoring (TDM) is the clinical practice of measuring drug concentrations or metabolites to attain a targeted concentration in a patient's bloodstream, thereby optimizing individual dosage regimens. With the well-established knowledge of the relationship of the genetic variability of thio-purine metabolism driven by the thiopurine S-methyltransferase pathway, and the recent data supporting pharmacokinetic variability and immunogenicity with anti-tumor necrosis factor (anti-TNF) therapies, TDM has emerged as a necessary mechanism to enhance drug efficacy. This article reviews data describing the relationship between drug concentrations and outcomes, including the achievement of a sustained and durable remission. The effect of antidrug antibodies on drug efficacy and toxicity is also examined. Furthermore, we describe different assays that are used for measuring these drug and antibody concentrations, including the advantages and pitfalls of these tools. An algorithm is proposed for clinical practitioners to utilize TDM in patients who are losing clinical response to anti-TNF therapy. A proactive, rather than reactive, approach to TDM of anti-TNF agents is supported by emerging data and will provide practitioners with the tools needed to optimally treat young inflammatory bowel disease patients.