Infliximab therapy intensification upon loss of response: Is there an optimal trough level?

Loss of response (LOR) to infliximab occurs in ∼30% of IBD patients. At time of LOR, lower infliximab-trough-levels (TL), in the absence of anti-drug-antibodies (ATI), have been associated with the need for therapy escalation. Nevertheless, few studies have examined the outcome of infliximab-therapy intensification, based on different TL.

To evaluate the impact of infliximab-TL on efficacy of therapy intensification (dose-elevation/interval-shortening).

This was a retrospective observational study performed at two tertiary-centers between 2013-2017. Study population included IBD patients who underwent infliximab therapy escalation (dose elevation/interval shortening) due to clinical LOR. Patients with TL < 3 μg/ml or positive ATI were excluded. TL and clinical scores before intensification and after 6, 12 months were obtained prospectively.

Forty-eight IBD patients were included; 23(49%), and 29(60%) reached clinical remission by 6, 12 months before intensification. TL among patients in clinical remission were significantly lower than among those clinically active, both at 6 (p = 0.001, median TL 4.7,8.7 μg/ml, IQR 3.6-8.1, 5.9-16 μg/ml) and 12 months (p = 0.005, median TL 4.6,8.7 μg/ml, IQR 3.6-8, 5.3-16 μg/ml), respectively.

In IBD patients experiencing clinical LOR to infliximab in the absence of ATI, success of doubling the dose was inversely associated with baseline TL. Patients with baseline TL above 9 mcg/ml were very unlikely to reach clinical remission.