Synthesis and biological evaluation of a potent E-selectin antagonist

An early step of the inflammatory response-the rolling of leukocytes on activated endothelial cells-is mediated by selectin/carbohydrate interactions. The tetrasaccharide sialyl Lewis(x) (sLe(x)) 1 is a ligand for E-, P-, and L-selectin and, therefore, serves as a lead structure to develop analogues which allow the control of acute and chronic inflammation. Here we describe the efficient synthesis (10 linear steps) of the potent sLe(x) mimetic 2. Compared to sLe(x), compound 2 showed a 30-fold improved affinity in a static, cell-free E-selectin-ligand binding assay (IC(50) = 36 microM). These data were confirmed by a marked inhibition in an in vitro cell-cell rolling assay which simulates in vivo conditions (IC(50) approximately 40 microM). The assays are predictive for the in vivo efficacy of test compounds as indicated by a marked inhibitory effect of 2 in a thioglycollate induced peritonitis model of acute inflammation in mice (ED(50) approximately 15 mg/kg).