Discovery and Biological Activity of Orally Active Peptidyl Trifluoromethyl Ketone Inhibitors of Human Neutrophil Elastase

Abstract

Previously we had shown that tripeptidyl trifluoromethyl ketones (TFMKs) possessing an N-terminal diarylacylsulfonamide, such as ICI 200,880 and ICI 200,355, displayed unparalleled protection against the lung damage induced by human neutrophil elastase (HNE) when the inhibitors were administered intratracheally. Since the diarylacylsulfonamides were designed specifically to afford a long residence time in the lung, it was not unexpected that inhibitors from this class of TFMKs were not active when administered orally. Upon evaluating a large number of peptidyl TFMKs possessing a variety of N-terminal groups, several compounds were identified which demonstrated oral activity. Compounds were evaluated for their oral activity by measuring their ability to inhibit the increase in lung weight relative to body weight (Lw/Bw), the increase in red blood cells, and the increase in white blood cells induced by intratracheally administered HNE (100 micrograms/hamster). A number of tripeptidyl trifluoromethyl ketones containing neutral N-terminal groups displayed good oral activity, while those containing basic, acidic, or polar groups did not. Compound 50, possessing an N-terminal 4-(CH3O)C6H4CO group, was particularly effective, reducing Lw/Bw by 77%, red cells by 89%, and white cells by 91% when dosed at 37.5 mg/kg orally. Thus, by modifying the N-terminal group of tripeptidyl TFMKs, inhibitors can be designed which are effective in vivo when administered either orally or intratracheally.

Structure-Activity Relationships for Inhibition of Cysteine Protease Activity and Development of Plasmodium falciparum by Peptidyl Vinyl Sulfones

“…Related phenyl vinyl sulfones also inhibit cruzain, a cysteine protease of Trypanosoma cruzi (31,32,35), and one of these compounds is currently undergoing preclinical studies for the treatment of Chagas' disease (34). While the clinical use of peptidyl protease inhibitors is potentially problematic due to limited bioavailability or poor pharmacokinetics, there are numerous recent reports of peptidyl inhibitors of renin (17), thrombin (11), leukocyte elastase (42), neutrophil elastase (8), and human immunodeficiency virus type 1 protease (2,16,40) that are biologically active after oral administration. Considering these data, the reported in vivo efficacy of an orally administered vinyl sulfone against murine malaria (22), and our demonstration here of marked antimalarial potency, additional evaluation of vinyl sulfonyl derivatives as potential antimalarial cysteine protease inhibitors seems appropriate.…”

Elastase and matrix metalloproteinase inhibitors induce regression, and tenascin-C antisense prevents progression, of vascular disease

“…GM-6001, an N-[2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl]-Ltryptophan methylamide, is a noncytotoxic, synthetic inhibitor that functionally and specifically inhibits MMP activity, by complexing with the zinc atom found in the active site of MMPs, and prevents substrate interaction, as described (18). 1K (ZD0892) is a peptidyl trifluoromethyl ketone with an N-terminal 4-(CH 3 O)C 6 H 4 CO group, making it an orally bioavailable serine elastase inhibitor (25). It is highly selective for neutrophil elastase (K i = 6.7 nM), but also inhibits pancreatic elastase (K i = 200 nM) and endogenous vascular elastase (unpublished data), but not other serine proteinases, or cysteine, or metalloproteinases.…”

The Dichotomy Between Understanding and Treating Emphysema

“…To further complicate matters, calpain [65] induces TNF-alpha mediated neutrophil chemotaxis and AAT binds to and inhibits calpain [66] thus preventing lung neutrophil infiltration by yet another mechanism. Even with all of this complexity and its implications that antioxidant therapy may be beneficial, the long established destructive role of unchecked elastase activity makes this enzyme a central target for inhibiting the progression of the alveolar wall destruction characteristic of emphysema as evidenced by the extensive pharmaceutical development that has gone into this endeavor, which includes small molecules from ONO [67], Merck [68], Zeneca [24], and Glaxo [69] (Figure 7). …”

“…Sawyer and colleagues deposited the first high resolution crystal structure of porcine pancreatic elastase [21] into the protein data bank, and in 1982 Hughes and colleagues [22] solved a structure of the enzyme bound to a trifluoroacetyl dipeptide inhibitor (deposited in the PDB in 1986), thus making high resolution structures with and without bound ligand available to the research community. The trifluoroacetyl motif (shown in Figure 1) became a cornerstone of Zeneca's small molecule research program [23][24][25][26][27][28][29][30][31][32], which resulted in the clinical candidate ICI 200,880 [33]that was halted due to lack of efficacy in Phase II clinical trials. Fig.…”