Serum Adalimumab Levels Predict Successful Remission and Safe Deintensification in Inflammatory Bowel Disease Patients in Clinical Practice

Background: Little is known about the association between the pharmacokinetic features of adalimumab (ADL) and disease outcome in patients with inflammatory bowel disease (IBD). Aims: To assess the association between random serum ADL levels and clinical or biochemical remission with clinical decision making in daily practice according to these levels; and to determine the cutoff value for successful dose reduction in patients with IBD treated with ADL. Methods: We conducted a prospective observational study of patients with IBD who received long-term maintenance therapy with ADL. Results: Data were available for 157 serum samples from 87 patients. Serum ADL levels were associated with clinical remission: median 9.2 versus 6.0 mu g/mL for patients with Crohn's disease with active disease (P = 0.009) and 14.4 versus 5.2 mg/mL in patients with ulcerative colitis with active disease (P = 0.002). Serum ADL levels were 9.2 mg/mL for patients with a normal C-reactive protein value (<5 mg/L) and 5.2 mu g/mL for patients with a high C-reactive protein value (P = 0.002). ADL levels were significantly associated with normal fecal calprotectin value (<80 ng/g) (10.8 versus 7.6 mu g/mL, respectively, P = 0.038). Serum ADL levels were significantly associated with successful deintensification, over a 6-month period of clinical follow-up, compared with the group in which doses remained unchanged (area under the curve 0.88; 95% confidence interval, 0.81-0.95; P < 0.001), with a cutoff value for successful deintensification of 12.2 mu g/mL. Conclusions: Higher ADA levels were significantly associated with clinical and biochemical remission. Our results, which were obtained under conditions of daily clinical practice, suggest that an ADL cutoff of 12.2 mu g/mL could be appropriate for successful dose reduction in patients with IBD treated with ADL.