OLIGONUCLEOTIDE INHIBITORS OF P-SELECTIN-DEPENDENT NEUTROPHIL-PLATELET ADHESION

P-selectin, an inducible cell adhesion molecule, mediates rolling of n eutrophils on activated vascular endothelium. Because rolling is an ea rly event of the inflammatory response, therapeutic applications of se lectin antagonists have been of broad interest. There are, however, no truly satisfactory therapeutic candidates among known inhibitors, Con sequently, we have used Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology, a process based on oligonucleotide com binatorial chemistry and in vitro selection, to develop aptamer antago nists of P-selectin, Equilibrium dissociation constants for aptamer/P- selectin binding range from 16 to 710 pM, a 10(5)-10(6)-fold improveme nt compared with the minimal carbohydrate ligand, sialyl Lewis X (sLe( X)). Aptamer binding is divalent cation dependent and, unlike sLeX, is specific for P-selectin, The selectivity for human P-selectin relativ e to human E-selectin or human L-selectin is 10(4)-10(5). In vitro, ap tamers bind with subnanomolar affinities to P-selectin expressed on th rombin-activated platelets, inhibit the binding of P-selectin-IgG chim era to sLeX and to neutrophils, and block the binding activated platel ets to neutrophils in flow cytometry and in hydrodynamic assays. Extra polating from their in vitro characteristics, these novel P-selectin-s pecific antagonists may be suitable candidates for therapeutic develop ment.