Novel Peptidyl α-Keto Amide Inhibitors of Calpains and Other Cysteine Proteases

• Published in: Journal of medicinal chemistry Vol. 39; no. 20; pp. 4089 - 4098
• Main Authors: Li, Zhaozhao, Ortega-Vilain, Anne-Cécile, Patil, Girish S, Chu, Der-Lun, Foreman, J. E, Eveleth, David D, Powers, James C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 27-09-1996
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Blood Platelets - metabolism; Blood Platelets - ultrastructure; Calpain - antagonists & inhibitors; Cathepsin B - antagonists & inhibitors; Cell Membrane Permeability; Cysteine Proteinase Inhibitors - chemical synthesis; Cysteine Proteinase Inhibitors - metabolism; Cysteine Proteinase Inhibitors - pharmacology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; Medical sciences; Molecular Structure; Neuropharmacology; Neuroprotective agent; Oligopeptides - chemical synthesis; Oligopeptides - metabolism; Oligopeptides - pharmacology; Pharmacology. Drug treatments; Rats; Structure-Activity Relationship; Peptides; Enzyme; Cysteine endopeptidases; Enzyme inhibitor; Calpain; Neuroprotective agent; Leucine; In vitro; Structure activity relation; Cathepsin B; Dipeptides; Hydrolases; Carboxamide; Chemical synthesis; Proteinases
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm950541c

A series of new dipeptidyl α-keto amides of the general structure R1-l-Leu-d,l-AA-CONH-R2 were synthesized and evaluated as inhibitors for the cysteine proteases calpain I, calpain II, and cathepsin B. They combine 10 different N-protecting groups (R1), 3 amino acids residues in P1 (AA), and 44 distinct substituents on the α-keto amide nitrogen (R2). In general, calpain II was more sensitive to these inhibitors than calpain I, with a large number of inhibitors displaying dissociation constants (K i) in the 10−100 nM range. Calpain I was also effectively inhibited, but very low K i values were observed with a smaller number of inhibitors than with calpain II. Cathepsin B was weakly inhibited by most compounds in this study. The best inhibitors for calpain II were Z-Leu-Abu-CONH-CH2-CHOH-C6H5 (K i = 15 nM), Z-Leu-Abu-CONH-CH2-2-pyridyl (K i = 17 nM), and Z-Leu-Abu-CONH-CH2-C6H3(3,5(OMe)2) (K i = 22 nM). The best calpain I inhibitor in this study was Z-Leu-Nva-CONH-CH2-2-pyridyl (K i = 19 nM). The peptide α-keto amide Z-Leu-Abu-CONH-(CH2)2-3-indolyl was the best inhibitor for cathepsin B (K i = 31 nM). Some compounds acted as specific calpain inhibitors, with comparable activity on both calpains I and II and a lack of activity on cathepsin B (e.g., 40, 42, 48, 70). Others were specific inhibitors for calpain I (e.g., 73) or calpain II (e.g., 18, 19, 33, 35, 56). Such inhibitors may be useful in elucidating the physiological and pathological events involving these proteases and may become possible therapeutic agents.