Anti-tumor Necrosis Factor Drug Concentration Is Not Associated with Disease Outcomes in Pouchitis: A Retrospective, International Study

Background: Therapeutic drug monitoring is important for optimizing anti-tumor necrosis factor-α (TNF-α) therapy in inflammatory bowel disease. However, the exposure–response relationship has never been assessed in pouchitis. Aims: To explore associations between anti-TNF-α drug concentration and pouchitis disease activity in patients with a background of ulcerative colitis. Methods: A retrospective, multicenter, cross-sectional study was conducted in adult patients with pouchitis requiring anti-TNF-α treatment. Rates of clinical and endoscopic remission were calculated, and drug concentrations during maintenance therapy were compared between remission and non-remission cohorts. Results: Sixty-three patients were included: median age, 48 years (IQR 36–59) and median time since pouchitis diagnosis, 7 years (IQR 2–13). Patients received infliximab, n = 27 (43%), adalimumab, n = 29 (46%), or both n = 7 (11%). Thirty-two (51%) patients received concomitant immunomodulation. Median infliximab trough concentrations (mg/ml) were similar between patients in clinical remission (n = 21) vs non-remission (n = 11), 5.3 vs. 4.4, p = 0.73. For adalimumab, median drug concentrations did not significantly differ between remission/non-remission groups based on clinical (n = 18/18), 11.4 vs 7.6, p = 0.32, or endoscopic assessment, (n = 7/29), 9.0 vs. 7.8, p = 0.78. Four patients had positive anti-drug antibodies with undetectable drug concentration. Conclusion: In a cohort of patients with pouchitis, higher anti-TNF-α drug concentrations were not associated with more clinical or endoscopic remission.