Comparison of Trough Level-based Spacing and Clinical-based Spacing of Infliximab Infusions in Patients With Inflammatory Bowel Disease in Deep Remission; A Prospective, Multicenter, Open-label, Randomized, Controlled Study

Infliximab (IFX) is common treatment for refractory inflammatory bowel disease (IBD) (5 mg/kg/8 weeks in maintenance). A large majority of IBD patients treated with IFX are currently in long-term clinical remission under maintenance IFX monotherapy or cotherapy with azathioprine or methotrexate. There is no recommendation on optimal duration of anti-TNF therapy once it is started. A key question is to know if the treatment could be stopped/decreased without clinical relapse. Anti-TNF therapy is also a major burden in health care costs in France. Identifying an optimal duration of anti-TNF therapy and criteria for stopping/decreasing could help in lowering these therapies cost without altering disease control. Prospective studies have investigated the withdrawal of IFX in IBD patients showing 50% of clinical relapse at 1 year in patient in clinical remission, 30% in patients in deep remission.

Another alternative to deescalate anti-TNF treatment would be to increase the infusion interval without stopping the drug. Indeed, this infusion interval spacing is strongly requested by patients who seek an improvement in their quality of life. This empirical spacing corresponded to an increase of the infusion interval to 10 weeks then to 12 weeks maximum in patients with persistent clinical remission. In France and in Europe, even if there is no recommendation about infliximab de-escalation and increase of the infusion interval, many physicians have already performed empirically an infliximab infusion interval spacing in IBD patients in longstanding remission while on infliximab maintenance therapy. This empirical infusion interval increase in patients in clinical remission leads to a clinical relapse in 30% of these patients with a median delay of 12.6 months (IQR: 10.4- 18.4) (Dufour et al. UEGW 2017).

Since the last ten years, it was demonstrated that the serum level of infliximab measured just before the last infliximab infusion (defined as a trough level) is correlated to the clinical activity of the disease1. A serum IFX trough level between 3 and 7 ug/ml has been identified as therapeutic with more clinical relapse in patients with IFX < 3 ug/ml and safe dose reduction in patients with IFX trough level > 7 ug/ml.

Thus, we hypothesized that using the determination of serum infliximab trough level could decrease the risk of clinical relapse observed in IBD patients who underwent an empirical infliximab infusion interval spacing (approximatively 30% of the cases). Indeed, in an infliximab trough level-based spacing strategy, only patients with a supratherapeutic (>7ug/ml) infliximab trough level would have a spacing of infliximab infusion.

The aim of our study is to compare an IFX infusion interval spacing strategy based on IFX trough level with an IFX infusion interval spacing strategy based on clinical evaluation for maintaining clinical and biological remission in IBD patients in deep remission.