Optimised infliximab monotherapy is as effective as optimised combination therapy, but is associated with higher drug consumption in inflammatory bowel disease.

BACKGROUND: Combination treatment with azathioprine for 6-12 months is the preferred strategy for starting infliximab due to improved pharmacokinetics. However, optimised infliximab monotherapy with proactive dose escalations in case of low trough levels is a safer but under-studied alternative. AIM: To compare the clinical success and infliximab consumption of combination vs optimised monotherapy strategies. METHODS: We studied the clinical success and infliximab consumption of both strategies in 149 patients (94 Crohn's disease; 55 ulcerative colitis) starting infliximab and undergoing intensive drug monitoring assisted treatment optimisation. RESULTS: The drug retention rates were similar for optimised monotherapy and combination treatment after induction (96% vs 97%, P = 0.73), after the first year (90% vs 83%, P = 0.23) and at the end of follow-up (74% vs 75%, P = 0.968). Similarly, no differences were observed for steroid use at year 1 (5% vs 14%, P = 0.08) or mucosal healing at the end of follow-up (64% vs 67%, P = 0.8). Higher infliximab consumption (7.6 mg/kg q8 weeks [interquartile range (IQR): 5.9-10.3] vs 6.4 mg/kg q8 weeks [IQR: 5.2-8.0], P = 0.019) combined with lower trough levels (1.7 µg/mL [IQR: 0.3-6.6] vs 5.0 µg/mL [2.5-8.7], P = 0.012) resulted in almost 3-fold higher drug-to-trough ratio (3.9 vs 1.5) in monotherapy compared to combination strategy at year 1. At the end of follow-up, when azathioprine had been discontinued for a median of 14 [IQR: 3-33] months, these differences disappeared. CONCLUSIONS: In this study, optimised infliximab monotherapy was as clinically effective as combination therapy but was associated with significantly higher infliximab consumption. The infliximab-sparing effect disappeared after azathioprine withdrawal.

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

OBJECTIVE: A prospective trial suggests target infliximab trough levels of 3-7 µg/mL, yet data on additional therapeutic benefits and safety of higher trough levels are scarce. AIM: To explore whether high infliximab trough levels (≥7 µg/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 <7 µg/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 66 mg/kg [30-257]; C-reactive protein 3 mg/L [3-3]) compared to trough levels below 7 µg/mL (fecal calprotectin 155 mg/kg [72-474]; C-reactive protein 3 mg/L [3-14.5]) (p < .001). High trough levels were superior also after excluding samples with trough levels <3 µg/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 <7 µg/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.