Selective Attenuation of the Extrinsic Limb of the Tissue Factor-Driven Coagulation Protease Cascade by Occupancy of a Novel Peptidyl Docking Site on Tissue Factor

Tissue factor (TF), the receptor and cofactor for factor VIIa (VIIa) for cellular initiation of the coagulation protease cascade, drives thrombogenesis, inflammation, tumor cell metastasis, and the lethality of severe sepsis. To identify TF surface loci that can selectively inhibit substrate zymogen association and activation, TF1 - 218, the extracellular domain, was used as the target for the phage display search. This resulted in selection of 59 clones from a phage gpVIII surface protein-expressed library of constrained combinatorial peptides. Of these, one encoding the peptide Glu-Cys-Leu-Arg-Ser-Val-Val-Thr-Cys on gpVIII most avidly bound TF1 - 218, as did the synthetic peptide. Inhibition of binding was selective with an IC50 of 30 nM for proteolytic activation of factor X by the TF1 - 218−VIIa complex. In contrast, there was no inhibition of factor IX activation. The selective inhibition of only factor X association with TF1 - 218 will spare the intrinsic hemostatic pathway while attenuating the extrinsic thrombogenic pathway. This and related peptidyl structures provide the potential for the more precise identification of TF surface loci that mediate selective functional properties of the protein as well as a structural basis for the design of novel molecules for selectively attenuating initiation of the extrinsic limb of the coagulation protease cascade and other functions of TF.