Inhibition of human leukocyte elastase by N-substituted peptides containing alpha,alpha-difluorostatone residues at P1.
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.
Skiles
J W
JW
Department of Medicinal Chemistry, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877.
Miao
C
C
Sorcek
R
R
Jacober
S
S
Mui
P W
PW
Chow
G
G
Weldon
S M
SM
Possanza
G
G
Skoog
M
M
Keirns
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D006224:Cricetinae; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D019272:Leukocyte Elastase; D008297:Male; D008647:Mesocricetus; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship; D014422:Turkeys
D006845:Hydrocarbons, Fluorinated; D009842:Oligopeptides; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase