Few data are available on the relevance of adalimumab (ADA) trough serum levels and anti-ADA antibodies (AAA) during long-term follow-up of patients with Crohn's Disease (CD), and their association with disease outcome. In this study, our aim was to assess ADA trough serum levels and the presence of AAA according to disease activity and clinical response during long-term follow-up in a series of patients with CD treated with ADA monotherapy.
We prospectively evaluated 23 consecutive, infliximab-naïve CD patients who achieved clinical remission/response after induction and were in maintenance treatment with ADA, and who were followed-up for at least 72 weeks. Blood samples were drawn at standardized time points to assess ADA through levels, AAA.
At week 48, we found significantly (p = 0.027) different ADA trough serum levels in patients in remission (10.1 mcg/mL), mild (7.4 mcg/mL), and moderate/severe disease (4.5 mcg/mL). Median ADA trough levels were significantly lower in patients with AAA (3.7 mcg/mL versus 9.3 mcg/mL, p = 0.006). At the end of follow-up (median 102 weeks, range 73-112 weeks), ADA trough serum concentrations were significantly higher (11.9 mcg/mL) as compared to patients with mild and moderate/severe disease (5.5 mcg/mL, p = 0.0002). Furthermore, median ADA trough concentrations showed a trend towards lower levels in AAA positive patients (5.2 mcg/mL versus 7.2 mcg/mL, p = 0.371).
Our results emphasize the relevance of therapeutic drug monitoring in CD patients on biologic treatment. ADA trough serum levels and the presence of AAA are important features in the management of patients on ADA treatment.