Hirulog peptides with scissile bond replacements resistant to thrombin cleavage

Abstract

Using the natural protein hirudin as a model, a novel class of synthetic peptide inhibitors were recently designed. These inhibitors, ‘hirulogs’, retain the carboxy terminal Hir 53–64 domain that interacts with the anion binding exosite of thrombin, connected via an oligoglycyl spacer unit to a catalytic site-directed moiety modeled on the sequence [D]Phe-Pro-Arg-X. The scissile Arg-X bond bond of substrate-like inhibitors has been modified to the proteolytic-resistant functions as β-homo amino acids Argψ[CH 2CONH] X ( 2) and reduced bond analogues Argψ[CH 2N]X ( 3). Both classes of compounds demonstrate inhibition of thrombin amidolytic activity, and this active-site inhibition is highly sensitive to the P 1′ residue X. Thus these hirulog deriviatives are resistant to thrombin proteolysis while maintaining substrate-like interactions with the active center. Finally, hirulog derivatives with non-cleavable replacements of the scissile bond are found to be effective anticoagulant agents.