A Readily Available, Highly Potent E-Selectin Antagonist

摘要

Excessive infiltration of leukocytes from blood vessels into surrounding tissues can cause acute or chronic inflammatory disorders such as reperfusion injuries, stroke, psoriasis, rheumatoid srthritis, or respiratory diseases. An early step in the cascade of events which finally lads to leukocyte extravasation-their rolling on activated endothelial cells-is mediated by selectin-carbohydrate interactions. The adverse effects could thus be prevented by selectin blockade. The tetrasaccharide sialyl Lewis~x (1, Scheme 1) is a weak ligand for E-, P- and L-selectin and became a lead to discover more potent inhibitors. To assess our E-selectin antagonists we used a static, cell-free ligand-binding assay which measures inhibition under equilibrium conditions. Sialyl Lewis~x (IC_(50)=1000-2000 #mu#M) was tested on each plate to allow direct comparison of data from different test plates. Thus, we obtained relative IC_(50) values (see Table 1). To further profile our compounds we developed a dynamic in vitro assay which allows to monitor E-selectin-dependent rolling of neutrophils on activated endothelial cells under shear stress and, hence, mimics the ninequilibrium in vivo conditions (see Table 1). Recently we described the promising E-selectin inhibitor 2 (Scheme 1), which showed good activities in both the static (rel. IC_(50)=0.030) and the dynamic (IC_(50)=10 #mu#M) assay. Here we report on our search for simplified analogues of 2 which led to the discovery of 3 (Scheme 1) being the most potent small-molecule E-selectin antagonist to date (IC_(50)=1-2 #mu#M in the dynamic flow assay).