Cysteine proteases related to mammalian interleukin-1 beta converting enzyme (ICE) and to its Caenorhabditis elegans homologue, CED-3, play a critical role in the biochemical events that culminate in apoptosis. We have determined the three-dimensional structure of a complex of the human CED-3 homologue CPP32/apopain with a potent tetrapeptide-aldehyde inhibitor. The protein resembles ICE in overall structure, but its S4 subsite is strikingly different in size and chemical composition. These differences account for the variation in specificity between the ICE- and CED-3-related proteases and enable the design of specific inhibitors that can probe the physiological functions of the proteins and disease states with which they are associated.

The results presented in this study establish a positional-scanning library as a powerful tool for rapidly and accurately assessing protease specificity. The preferred sequence for ICE (WEHD) differs significantly from that found in human pro-interleukin-1beta (YVHD), which suggests that this protease may have additional endogenous substrates, consistent with evidence linking it to apoptosis and IL-1alpha production.

Caspases are cysteine proteases that specifically cleave Asp-Xxx bonds. They are key agents in inflammation and apoptosis and are attractive targets for therapy against inflammation, neurodegeneration, ischemia, and cancer. Many caspase structures are known, but most involve either peptide or protein inhibitors, unattractive candidates for drug development. We present seven crystal structures of inhibited caspase-3 that illustrate several approaches to reducing the peptidyl characteristics of the inhibitors while maintaining their potency and selectivity. The inhibitors reduce the peptidyl nature of inhibitors while preserving binding potency by (1). exploiting a hydrophobic binding site C-terminal to the cleavage site, (2). replacing the negatively charged aspartyl residue at P4 with neutral groups, and (3). using a peptidomimetic 5,6,7-tricyclic system or a pyrazinone at P2-P3. In addition, we have found that two nicotinic acid aldehydes induce a significant conformational change in the S2 and S3 subsites of caspase-3, revealing an unexpected binding mode. These results advance the search for caspase-directed drugs by revealing how unacceptable molecular features can be removed without loss of potency.

The above differences account for the variation in substrate specificity among granzyme B, other serine proteases and the caspases, and enable the design of specific inhibitors that can probe the physiological functions of these proteins and the disease states with which they are associated.

In this MTOPS data analysis long-term (more than 4 years) treatment with finasteride, either alone or in combination with doxazosin, led to a consistent, clinically significant reduction in total prostate volume compared to placebo in patients with lower urinary tract symptoms and benign prostatic hyperplasia whose baseline prostate size ranged from relatively small (less than 25 to 30 ml) to enlarged (40 ml or greater).