PURPOSE OF REVIEW: We review the most recent developments regarding the 
targeting of molecules involved in the traffic of leukocytes for the treatment 
of inflammatory bowel diseases (IBD).
RECENT FINDINGS: We discuss the most important findings of one published phase 
II trial that targeted the β7 integrin (etrolizumab), two phase II trials that 
targeted the α4β7 integrin ligand: mucosal addressin cell adhesion molecule 1 
(MAdCAM-1, PF-00547659), a phase II trial targeting the chemokine IP-10 (CXCL10) 
in Crohn's, and a phase II trial that targeted the sphingosine-1-phosphate 
receptor-1: ozanimod in patients with ulcerative colitis.
SUMMARY: Targeting molecules involved in leukocyte traffic has recently become 
an effective and well tolerated strategy for the treatment of IBD. Novel 
approaches now not only target the integrins on the lymphocyte surface, but also 
its endothelial ligand: MAdCAM-1. As with vedolizumab, antibodies against 
MAdCAM-1 appear most effective in ulcerative colitis rather than in Crohn's. 
Targeting chemokines or their receptors does not appear to have the same 
efficacy as those that target the most stable integrin: immunoglobulin 
superfamily interactions between the lymphocyte and endothelium. Preliminary 
results also suggest that the sphingosine-1-phosphate pathway might also be 
targeted therapeutically in IBD, no longer with parenterally administered 
antibodies but with orally administered small molecules.