Inhibition of human leukocyte elastase by N-substituted peptides containing .alpha.,.alpha.-difluorostatone residues at P1

• Published in: Journal of medicinal chemistry 1992-12, Vol.35 (26), p.4795-4808
• Main Authors: Skiles, Jerry W, Miao, Clara, Sorcek, Ronald, Jacober, Stephen, Mui, Philip W, Chow, Grace, Weldon, Steve M, Possanza, Genus, Skoog, Mark
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Binding Sites - drug effects; Biological and medical sciences; Cricetinae; Humans; Hydrocarbons, Fluorinated - chemical synthesis; Hydrocarbons, Fluorinated - chemistry; Hydrocarbons, Fluorinated - pharmacology; Immunomodulators; Leukocyte Elastase; Male; Medical sciences; Mesocricetus; Models, Molecular; Molecular Sequence Data; Oligopeptides - chemical synthesis; Oligopeptides - chemistry; Oligopeptides - pharmacology; Pancreatic Elastase - antagonists & inhibitors; Pharmacology. Drug treatments; Structure-Activity Relationship; Turkeys
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm00104a004

A series of tripeptides which contain alpha,alpha-difluorostatone residues at P1-P1' and span the S3-S1' subsites have been shown to be potent inhibitors of human leukocyte elastase (HLE). The tripeptides described contain the nonproteinogenic achiral residue N-(2,3-dihydro-1H-inden-2-yl)glycine at the P2-position. This redidue has previously been shown in the case of HLE to be a good bioisosteric replacement for L-proline. Of the peptides prepared, those which contain the alpha,alpha-difluoromethylene keton derivative of L-valine (difluorostatone) are the preferred residue at the P1-primary specificity position. Substitution at P1 by the corresponding alpha,alpha-difluoromethylene ketones of L-leucine and L-phenylalanine gives inactive compounds. Of the tripeptides described the most potent in vitro compound is ethyl N-[N-CBZ-L-valyl-N-(2,3-dihydro-1H-inden-2-yl)glycyl]- 4(S)-amino-2,2-difluoro-3-oxo-5-methylhexanoate (17B) (IC50 = 0.635 microM). It is presumed that the inhibitor 17b interacts with the S3-S1' binding regions of HLE. Additionally extended binding inhibitors were prepared which interact with the S3-S3' binding subsites of HLE. In order to effect interaction with the S1'-S3' subsites of HLE, the leaving group side of cleaved peptides, spacers based upon Gly-Gly, and those linked via the N epsilon of L-lysine were utilized. One of the most potent extended compounds (P3-P3') in vitro is methyl N6-[4(S)-[[N-[N-CBZ-L-valyl-N- (2,3-dihydro-1H-inden-2-yl)glycyl]amino]-2,2-difluoro-3-oxo-5- methylhexanoyl]-2(S)-(acetylamino)-6-aminohexanoate (24b) (IC50 = 0.057 microM). The described in vitro active inhibitors were also evaluated in hamsters in an elastase-induced pulmonary hemorrhage (EPH) model. In this model, intratracheal (it.) administration of 22c, 5 min prior to HLE challenge (10 micrograms, it.) effectively inhibited hemorrhage (94.6%) in a dose-dependent manner. The described alpha,alpha-difluoromethylene ketone inhibitors are assumed to act as transition-state analogs. The inhibition process presumably acts via hemiketal formation with the active site Ser195 of HLE, and is facilitated by the strongly electron withdrawing effect of the alpha,alpha-difluoromethylene functionality.