Pediatric and adolescent Crohn’s disease patients who switch to infliximab after losing responsiveness to adalimumab display lower drug concentrations in their blood than those receiving infliximab as their first biologic. However, a real-world study reveals that both groups achieve nearly identical rates of endoscopic remission after one year, demonstrating that lower blood drug levels do not necessarily translate to reduced therapeutic efficacy.
Samsung Medical Center announced that a pediatric research team led by Professors Kwon Yi-young and Kim Mi-jin analyzed 469 pediatric and adolescent Crohn’s disease patients treated with infliximab. Their findings, published in the August 2026 issue of the international medical journal Inflammatory Bowel Diseases, suggest that clinicians must interpret therapeutic drug monitoring results within the broader context of a patient's prior treatment history.
Comparable Intestinal Healing Despite Varied Drug Concentrations
Crohn’s disease is a chronic inflammatory condition that can affect any part of the gastrointestinal tract, causing abdominal pain, persistent diarrhea, weight loss, and impaired physical growth in children and teens. Both infliximab and adalimumab are biologic therapies that target tumor necrosis factor (TNF), a key mediator of inflammation. While both drugs target the same inflammatory pathway, infliximab is administered as an intravenous infusion in a clinical setting, whereas adalimumab is delivered as a subcutaneous injection.
The research team evaluated 372 patients who received infliximab as their initial biologic therapy alongside 97 patients who switched to infliximab after treatment with adalimumab.
After approximately one year of therapy, endoscopic remission—defined as the subsidence of visible mucosal inflammation—was achieved by 61.3% of the biologic-naive group and 58.8% of the switcher group, a difference that was not statistically significant.
Conversely, infliximab trough concentrations—measured immediately prior to the next scheduled dose—averaged 6.19 µg/mL in the first-time group compared to 4.73 µg/mL in the group previously treated with adalimumab. Despite these significantly lower blood drug levels among switchers, overall clinical and endoscopic outcomes remained comparable between the two cohorts.
Treatment Strategy Requires Holistic, Individualized Assessment
The research team emphasized that these findings should not be interpreted as a justification for intentionally targeting lower infliximab blood concentrations in patients with prior adalimumab exposure.
Because the study was a retrospective real-world analysis, baseline differences existed between the two patient groups, including age, body mass index (BMI), and total disease duration prior to initiating infliximab. Consequently, researchers highlighted that drug efficacy should not be judged by blood concentration in isolation.
"Because pediatric Crohn’s disease requires long-term management, clinicians must evaluate a patient’s overall treatment course rather than focusing solely on the response to a single drug," said Professor Kim Mi-jin. "A tailored management strategy is essential—one that interprets therapeutic drug concentrations alongside inflammatory markers, body mass index, and prior biologic history."
