Commentary

Increasing insights into the underlying immunopathogenic mechanisms of inflammatory bowel diseases (IBD) have led to the advent of targeted therapies, which selectively inhibit crucial mediators or signalling pathways of the intestinal inflammatory process. Here, the anti-integrin antibody vedolizumab is believed to block the integrin α4β7 on gut homing T cells, leading to diminished trafficking of these cells to the intestinal mucosa thereby ameliorating the inflammatory process.1 However, recent studies have implicated that vedolizumab also binds to a wider range of α4β7-expressing immune cells, like non-classical monocytes, indicating the multilayered immunomodulatory impact of vedolizumab treatment in IBD.2 Furthermore, there are no data regarding the distribution of vedolizumab in the intestinal tissue of patients with IBD to further elucidate its perceived mode of mechanism.

In Gut, Gabriëls et al report a phase 1 feasibility study where in vivo fluorescence molecular imaging (FMI) was applied in conjunction with intravenously applied fluorescent labelled vedolizumab to visualise its intestinal distribution and identify mucosal target cells in patients with IBD.3 In vivo FMI was performed by inserting a fibre bundle coupled to the custom-built endoscope through the working channel of the endoscope. The authors manufactured fluorescent vedolizumab (vedo-800CW) under Good Manufacturing Practice conditions and initially applied it in different doses, 2–4 days prior to endoscopy in five patients with IBD. Interim macroscopic in vivo and microscopic ex vivo analyses demonstrated a dose-dependent increase in vedo-800CW mediated fluorescence in inflamed tissues. Here, the tested 15 mg dose provided …