Vercirnon (GSK1605786A) sodium is an orally bioavailable, selective, and potent antagonist of CCR9. Vercirnon sodium inhibits CCR9-mediated Ca2+ mobilization and chemotaxis on Molt-4 cells with IC50 values of 5.4 and 3.4 nM, respectively. Vercirnon sodium is selective for CCR9 over CCR1-12 and CX3CR1-7 (IC50s>10 μM for all). Vercirnon sodium is an equipotent inhibitor of CCL25-directed chemotaxis of both splice forms of CCR9 (CCR9A and CCR9B) with IC50 values of 2.8 and 2.6 nM, respectively.