P851 Therapeutic drug monitoring of infliximab and adalimumab versus clinical control during maintenance therapy in patients with Inflammatory Bowel Disease

Abstract

Abstract Background Although it is known that the levels of infliximab or adalimumab are correlated with clinical response, there is controversy about the best strategy to follow in patients with Inflammatory Bowel Disease (IBD) in remission and undergoing maintenance treatment. Methods We conducted a randomized, prospective, single-blinded, and multicentre trial in patients with Crohn’s Disease (CD) or Ulcerative Colitis (UC) who have remained in clinical remission for at least 12 weeks and are receiving adalimumab (ADA) or infliximab (IFX) as maintenance treatment. Patients were assigned to two groups. In the first group, patient management was done considering therapeutic drug monitoring (TDM). In the second, according to usual clinical practice (CP). The optimal serum range was within 3-7µg/ml and 5-8µg/ml for IFX and ADA respectively, based on the use of Promonitor-IFX, and Promonitor-ADL kits. The primary endpoint was to maintain patients in clinical remission (target >16% between both groups at 12 months) and diminish the frequency of flare-ups. Results In total, 209 patients were randomized, 29 UC (27.6%), 76 CD (72.4%) as the clinical practice group, and 24 UC (23.1%), 80 CD (76.9%) as the drug monitoring therapeutic group. Infliximab was administered in 105 patients and adalimumab in 104. Remission at the end of the study was achieved in 98.1% of the proactive dosing group and 90.5% of the clinical practice group (p=0.02), with a difference between both groups of 7.6%. The number of flare-ups was 1.3/10 patient-years in the TDM group and 2.4/10 patient-years in the CP group. The IRR of flare-up throughout the study was 0.71 (95% CI 0.32 – 1.55). In the group with IFX: IRR = 0.56 (95% CI 0.08 – 3.81) and with ADA: 0.78 (95% CI 0.29-2.16). The changes made in the drug dose are shown in Table 1. Conclusion Differences were found in favour of the TDM group, with increasing remission rates (7.6%) and half number of flare-ups. However, the pre-established effectiveness remission target (16%) was not met. In the subgroup of patients with Infliximab, management through TDM seems to have an advantage over usual clinical control.