Janus compounds: dual inhibitors of proteinases

Nonpeptide inhibitors of cathepsin G: optimization of a novel beta-ketophosphonic acid lead by structure-based drug design

The serine protease cathepsin G (EC 3.4.21.20; Cat G), which is stored in the azurophilic granules of neutrophils (polymorphonuclear leukocytes) and released on degranulation, has been implicated in various pathological conditions associated with inflammation. By employing high-throughput screening, we identified beta-ketophosphonic acid 1 as a moderate inhibitor of Cat G (IC(50) = 4.1 microM). We were fortunate to obtain a cocrystal of 1 with Cat G and solve its structure by X-ray crystallography (3.5 A). Structural details from the X-ray analysis of 1.Cat G served as a platform for optimization of this lead compound by structure-based drug design. With the aid of molecular modeling, substituents were attached to the 3-position of the 2-naphthyl ring of 1, which occupies the S1 pocket of Cat G, to provide an extension into the hydrophobic S3 region. Thus, we arrived at analogue 7 with an 80-fold potency improvement over 1 (IC(50) = 53 nM). From these results, it is evident that the beta-ketophosphonic acid unit can form the basis for a novel class of serine protease inhibitors.

Inhibition of cathepsin G by 4H-3,1-benzoxazin-4-ones

A series of 4H-3,1-benzoxazin-4-ones is reported that inhibit the serine proteases human cathepsin G and bovine chymotrypsin. The synthesis and kinetic parameters of the alkaline hydrolysis is described. These compounds act as acyl-enzyme inhibitors of both enzymes. The reaction of cathepsin G with 2-benzylamino-4H-3,1-benzoxazin-4-one (20) was studied in detail. A partition in deacylation of the initially formed acyl-enzyme was observed, leading to the formation of 2-(3-benzylureido)benzoic acid (26) and 3-benzylquinazoline-2,4-(1H,3H)-dione (27). A 6-methyl substitution strongly increased the acylation rate of both proteases. Introduction of an aryl moiety into the 2-substituent led to compounds with Ki values towards cathepsin G in the nanomolar range. Their inhibitory potency is stronger than that of other synthetic inhibitors of cathepsin G.

Inhibition of human neutrophil elastase and cathepsin G by a biphenyl disulfonic acid copolymer

The sulfated polymer MDL 101,028 was found to be a potent-inhibitor of both human neutrophil elastase (HNE) and human neutrophil cathepsin G (CatG). Cleavage of synthetic substrate by HNE was inhibited by MDL 101,028 with an IC50 of 40 nM, while CatG was inhibited with an IC50 of 80 nM. Degradation of a macromolecular connective tissue substrate (cartilage proteoglycan) by HNE or CatG was inhibited by MDL 101,028 with an IC50 of approximately 10 microM. MDL 101,028 at concentrations of 4, 10 and 25 microM inhibited degradation of cartilage proteoglycan by human neutrophil lysate or stimulated human neutrophils by 54%, 70% and 79%, and 31%, 47% and 73%, respectively. Acute pulmonary injury resulting from the intratracheal (i.t.) instillation of HNE in rats was inhibited by 48%, 90% and 90% at concentrations of MDL 101,028 of 1.1 mg/kg, 2.8 mg/kg and 11 mg/kg. The duration of action of the compound after i.t. instillation was between 2 and 4 h. These results suggest that sulfated polymers such as MDL 101,146 may be useful as inhibitors of HNE-mediated lung injury.