Design, synthesis and biological activity of novel peptidyl benzyl ketone FVIIa inhibitors

Herein is described the synthesis of a novel class of peptidyl FVIIa inhibitors having a C-terminal benzyl ketone group. This class is designed to be potentially suitable as stabilization agents of liquid formulations of rFVIIa, which is a serine protease used for the treatment of hemophilia A and B inhibitor patients. A library of compounds was synthesized with different tripeptide sequences, N-terminals and D-amino acids in the P3 position. Cbz-D-Phe–Phe–Arg–bk (33) was found to be the best candidate with a potency of Ki = 8 lM and no substantial inhibition of related blood coagulation factors (thrombin and FXa). Computational studies revealed that 33 has a very stable binding conformation due to intramolecular hydrogen bonds, which cannot be formed with L-Phe in the P3 position. Nonpolar amino acids were found to be superior, probably due to a minimization of the cost of desolvation upon binding to FVIIa.