A New Strategy for the Development of Highly Potent and Selective Plasmin Inhibitors

Department of Pharmacy, Institute of Pharmaceutical Chemistry, Philipps University Marburg, Marbacher Weg 6, D-35032 Marburg, Germany.
Journal of Medicinal Chemistry (Impact Factor: 5.45). 02/2012; 55(3):1171-80. DOI: 10.1021/jm2011996
Source: PubMed


A new structure-based strategy for the design of potent and selective plasmin inhibitors was developed. These compounds could be prepared by cyclizations between the P3 and P2 amino acid residues of substrate-analogue inhibitors using metathesis or a copper-catalyzed azide alkyne cycloaddition in combination with standard peptide couplings. The most potent bis-triazole derivative 10 inhibits plasmin and plasma kallikrein with K(i) of 0.77 and 2.4 nM, respectively, whereas it has poor activity against the related trypsin-like serine proteases thrombin, factor Xa, or activated protein C. Modeling experiments revealed that inhibitor 10 adopts a compact and rigid structure that fits well into the relatively open active site of plasmin and plasma kallikrein, while it is rejected from sterically demanding residues present in loops of the other enzymes. These results from modeling confirm the selectivity profile found for inhibitor 10 in enzyme kinetic studies. Such compounds might be useful lead structures for the development of new antifibrinolytic drugs for use in cardiac surgery with cardiopulmonary bypass or organ transplantations to reduce bleeding complications.

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    ABSTRACT: The benzamidine moiety, a well-known arginine mimetic, has been introduced in a variety of ligands, including peptidomimetic inhibitors of trypsin-like serine proteases. According to their primary substrate specificity, the benzamidine residue interacts with the negatively charged aspartate at the bottom of the S1 pocket of such enzymes. Six series of benzamidine derivatives (1-73) were synthesized and evaluated as inhibitors of two prototype serine proteases, that is, bovine trypsin and human thrombin. As a further target, human matriptase-2, a recently discovered type II transmembrane serine protease, was investigated. Matriptase-2 represents an important regulatory protease in iron homeostasis by down-regulation of the hepcidin expression. Compounds 1-73 were designed to contain a fixed sulfamoyl benzamidine moiety as arginine mimetic and a linker-connected additional substructure, such as a tert-butyl ester, carboxylate or second benzamidine functionality. A systematic mapping approach was performed with these inhibitors to scan the active site of the three target proteases. In particular, bisbenzamidines, able to interact with both the S1 and S3/S4 binding sites, showed notable affinity. In branched bisbenzamidines 66-73 containing a third hydrophobic residue, opposite effects of the stereochemistry on trypsin and thrombin inhibition were observed.
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    No preview · Article · Oct 2012 · Journal of Peptide Science
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    ABSTRACT: The trypsin-like serine protease plasmin is a target for the development of antifibrinolytic drugs for use in cardiac surgery with cardiopulmonary bypass or organ transplantations to reduce excessive blood loss. The optimization of our recently described substrate-analogue plasmin inhibitors, which were cyclized between their P3 and P2 side chains, provided a new series with improved efficacy and excellent selectivity. The most potent inhibitor 8 binds to plasmin with an inhibition constant of 0.2 nM, whereas Ki values > 1 µM were determined for nearly all other tested trypsin-like serine proteases, with the exception of trypsin, which is also inhibited in the nanomolar range. Docking studies revealed a potential binding mode in the widely open active site of plasmin that explains the strong potency and selectivity profile of these inhibitors. The dialkylated piperazine-linker segment contributes to an excellent solubility of all analogues. Based on their overall profile the presented inhibitors are well suited for further development as injectable antifibrinolytic drugs.
    No preview · Article · Jan 2013 · Journal of Medicinal Chemistry
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