Success and safety of high infliximab trough levels in inflammatory bowel disease

Objective: A prospective trial suggests target infliximab trough levels of 3-7g/mL, yet data on additional therapeutic benefits and safety of higher trough levels are scarce.Aim: To explore whether high infliximab trough levels (7g/mL) are more effective and still safe.Material and methods: In this cohort study of 183 patients (109 Crohn's disease and 74 ulcerative colitis) on infliximab maintenance treatment at a tertiary referral center we correlated fecal calprotectin and C-reactive protein to trough levels (426 samples) at different time points during treatment. Rates of infections were compared in quadrimesters (four-month periods) with high trough levels to quadrimesters with trough levels <7g/mL during 420 patient-years.Results: Fecal calprotectin and C-reactive protein (median [interquartile range]) were lower in patients with high trough levels (fecal calprotectin 66mg/kg [30-257]; C-reactive protein 3mg/L [3-3]) compared to trough levels below 7g/mL (fecal calprotectin 155mg/kg [72-474]; C-reactive protein 3mg/L [3-14.5]) (p<.001). High trough levels were superior also after excluding samples with trough levels <3g/mL from analysis. No differences in rates of infections were observed in quadrimesters with high trough levels (16/129 [12.4%]) compared to quadrimesters with trough levels <7g/mL (32/344 [9.3%]) (p=.32). Maintaining high trough levels resulted in 32% (interquartile range: 2-54%) increase of infliximab consumption.Conclusion: High infliximab trough levels provide better control of inflammation in inflammatory bowel disease without increasing the risk of infection.