The invention relates to peptide mimetics comprising the residues P4-P3-P2-P1, which were cyclized between the side chains of P3 and P2 amino acid and are, as inhibitors of the serine protease plasmin, suitable to be used to inhibit fibrinolysis and thus to reduce blood loss in hyperfibrinolytic conditions, for example during surgery.
The invention relates to peptide mimetics comprising the residues P4-P3-P2-P1, which were cyclized between the side chains of P3 and P2 amino acid and are, as inhibitors of the serine protease plasmin, suitable to be used to inhibit fibrinolysis and thus to reduce blood loss in hyperfibrinolytic conditions, for example during surgery.
New macrocyclic plasmin inhibitors based on our previously optimized P2-P3 core segment have been developed. In the first series, the P4 residue was modified, whereas the 4-amidinobenzylamide in P1 position was maintained. The originally used P4 benzylsulfonyl residue could be replaced by various sulfonyl- or urethane-like protecting groups. In the second series, the P1 benzamidine was modified and a strong potency and excellent selectivity was retained by incorporation of p-xylenediamine. Several analogues inhibit plasmin in the subnanomolar range, and their potency against related trypsin-like serine proteases including trypsin itself could be further reduced. Selected derivatives have been tested in a plasma fibrinolysis assay and are more effective than the reference inhibitor aprotinin. The crystal structure of one inhibitor was determined in complex with trypsin. The binding mode reveals a sterical clash of the inhibitor's linker segment with the 99-hairpin loop of trypsin, which is absent in plasmin.