New cathepsin d inhibitors with hydroxyethylamine isosteres: preparation and characterization.

The lysosomal aspartyl protease, cathepsin D, has been suggested to play a role in the metastatic potential of several types of cancer. Cathepsin D is secreted by malignant cells, and is believed to be involved in the breakdown of the extracellular matrix. High levels of active cathepsin D have been found in colon cancer, prostate cancer, uterine cancer and ovarian cancer. Also cathepsin D has recently been associated with the development of Alzheimer's disease. Hydroxyethyl isosteres with cyclic tertiary amine have proven to be clinically useful as inhibitors of aspartyl proteases similar to cathepsin D in activity, such as the HIV-1 aspartyl protease. In the present study twenty-eight compounds containing (hydroxyethyl)amine isosteres with cyclic tertiary amines have been synthesized. These compounds show significant activity as cathepsin D inhibitors, many with IC(50) values in the nanomolar range. For example, the compounds that contain hydroxyethylamines where the amine is formed from N-piperazine-2-carboxylic acid methyl ester, 4y-bb, show IC(50) values ranging from 2.5 to 15 nM.

Inhibition studies of some serine and thiol proteinases by new leupeptin analogues.

Fifteen tripeptide analogues of leupeptin containing either a C-terminal argininal or lysinal were synthesized. The synthetic analogues were tested, using spectrophotometric assay techniques, as inhibitors of trypsin, kallikrein, thrombin, plasmin, and cathepsin B. The lysinal analogues were fairly selective as inhibitors of cathepsin B activity. Acetyl-L-leucyl-L-valyl-L-lysinal (21) showed a stronger inhibition of cathepsin B (IC50 = 4 nanomolar) than leupeptin. Acetyl-L-phenylalanyl-L-valyl-L-argininal (2i) was found to be a good inhibitor of cathepsin B (IC50 = 0.039 microM), thrombin (IC50 = 1.8 microM), and plasmin (IC50 = 2.2 microM).

New leupeptin analogues: synthesis and inhibition data.

Syntheses of several tripeptide analogues of leupeptin containing C-terminal argininal, lysinal, or ornithinal units are presented. The synthetic analogues were tested as inhibitors of trypsin, plasmin, and kallikrein. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) was significantly less effective as an inhibitor of trypsin and plasmin activity than leupeptin. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) and (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) display different inhibition characteristics than (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a). While (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) showed moderate inhibition of all three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) was less effective as an inhibitor of trypsin and plasmin activity. Of the three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) showed significant inhibition of kallikrein activity only. Modifications made in the composition and sequence of the P2 and P3 amino acids also resulted in variations in the inhibitory activity of the analogues. In general, plasmin showed a strong preference for inhibitors which contain an L-phenylalanyl-L-leucyl or an L-leucyl-L-valyl unit in the P2 and P3 positions.