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O-003 YI Drug Level Versus Clinically Based Dosing of Infliximab Maintenance Therapy In IBD: Final Results of the Randomized Controlled Taxit Trial

BACKGROUND: Treat-to-target dosing based on infliximab (IFX) trough levels (TLI) has been suggested to increase efficacy, safety and cost-effectiveness of IFX treatment, although prospective data are lacking. In the optimization phase of the TAXIT study we showed that dose intensification of IFX in CD patients with TLI <3 µg/mL resulted in a better disease control, whereas dose reduction in CD and UC patients with TLI >7 µg/mL resulted in lower drug exposure and lower IFX cost whilst maintaining disease control (Vande Casteele N, et al. Gastroenterology 2012;142(5):S211–S212). METHODS: Here we report on the subsequent long-term randomized part of this study. Two hundred fifty-one patients entered the maintenance phase (MP) of which 123 patients (82 CD/41 UC) were randomized to the clinically based (CB) arm and 128 patients (91 CD/37 UC) to the trough level based (LB) arm. Primary end point of the MP was the rate of both clinical (Harvey-Bradshaw/partial MAYO score) and biological (CRP ⩽5 mg/l) remission 1 year after randomization in each group. Secondary end points included number of patients with TLI between 3–7 µg/mL and antibody to IFX (ATI) rate. RESULTS: After optimization, median TLI and CRP were equal in the CB and LB arm (respectively 4.9 µg/mL [3.8–5.9] versus 5.0 µg/mL [4.0–5.7] and 1.3 mg/l [0.6–4.5] versus 1.5 mg/l [0.7–4.1]). 226/251 patients (90%) completed the MP of whom 69% of the CB versus 72% of the LB arm achieved the primary end point (P = 0.7). During MP, 11 patients (4.4%) (5 CB versus 6 LB) were failures and 14 patients (5.6%) (7 CB versus 7 LB) were excluded (e.g. due to pregnancy or lost to follow-up). After 1 year, 56% in the CB versus 78% in the LB arm had TLI between 3–7 µg/mL (P < 0.001). During MP, undetectable TLI were more frequently observed in the CB than in the LB arm (RR 3.7; 95% CI 1.7–8.0; P < 0.001) which may have influenced the higher frequency rate of ATI observed in the CB versus the LB arm (RR 3.3; 95% CI 1.4–7.7; P < 0.01). At the end of MP, 3 patients were ATI positive in the CB versus none in the LB arm (P = 0.1). All 3 patients were ATI negative at screening and developed ATI during MP. CONCLUSIONS: Dose-to-target optimization of IFX allowed to achieve TLI within the interval of 3–7 µg/mL which resulted in a more efficient use of drug. The maintenance phase did not show superiority for continued level based drug adjustment over clinically based adjustment. Treatment guided by levels resulted in less ATI formation but the proportion of patients in clinical and biological remission was similar for both groups.