Infliximab trough levels and persistent vs transient antibodies measured early after induction predict long-term clinical remission in patients with inflammatory bowel disease

Background: The use of therapeutic drug monitoring has been proposed as a useful tool in the management of patients with loss of response to biological therapy in patients with inflammatory bowel disease. Aims: To evaluate whether early, post-induction anti-tumor necrosis factor trough levels and the presence of different types of anti-drug antibodies may impact long-term clinical remission in patients with inflammatory bowel disease. Methods: We prospectively assessed anti-tumor necrosis factor trough levels and both persistent and transient anti-drug antibodies. The Harvey-Bradshaw Index and the partial Mayo score were evaluated at each visit or in case of relapse. Results: At week 14, median infliximab trough levels were significantly lower in patients who experienced loss of response at week 48 as compared to patients in stable remission (1.3. mcg/mL [range 0-10.2. mcg/mL] vs. 10.1. mcg/mL[range 0-42.8. mcg/mL], P< 0.0004). ROC curve identified an infliximab trough levels of 6.2. mcg/mL as the cut-off value with the highest accuracy (c-index = 0.864) for loss of response at week 48. At week 14 we observed a correlation between anti-drug antibodies concentration and infliximab trough levels (rs= -0.513, P = 0.04). Conclusions: The results highlight the usefulness of assessing early biological TL in order to predict patients' long-term outcome.