Peptides with 6-Aminohexanoic Acid: Synthesis and Evaluation as Plasmin Inhibitors.

Fifteen new peptide derivatives of ɛ-aminocaproic acid (EACA) containing the known fragment -Ala-Phe-Lys- with an affinity for plasmin were synthesised in the present study. The synthesis was carried out a solid phase. The following compounds were synthesised: H-Phe-Lys-EACA-X, H-d-Ala-Phe-Lys-EACA-X, H-Ala-Phe-Lys-EACA-X, H-d-Ala-Phe-EACA-X and H-Ala-Phe-EACA-X, where X = OH, NH2 and NH-(CH2)5-NH2. All peptides, except for those containing the sequence H-Ala-Phe-EACA-X, displayed higher inhibitory activity against plasmin than EACA. The most active and selective inhibitor of plasmin was the compound H-d-Ala-Phe-Lys-EACA-NH2 which inhibited the amidolytic activity of plasmin (IC50 = 0.02 mM), with the antifibrinolytic activity weaker than EACA. The resulting peptides did not affect the viability of fibroblast cells, colon cancer cell line DLD-1, breast MCF-7 and MDA-MB-231 cell lines.