A lead compound obtained from a high volume human non-pancreatic secretory phospholipase A2 (hnps-PLA2) screen has been developed into a potent inhibitor using detailed structural knowledge of inhibitor binding to the enzyme active site. Four crystal structures of hnps-PLA2 complexed with a series of increasingly potent indole inhibitors were determined and used as the structural basis for both understanding this binding and providing valuable insights for further development. The application of structure-based drug design has made possible improvements in the binding of this screening lead to the enzyme by nearly three orders of magnitude. Furthermore, the optimized structure (LY311727) displayed 1,500-fold selectivity when assayed against porcine pancreatic s-PLA2.

Phospholipases (PLAs) produce rate-limiting precursors in the biosynthesis of various types of biologically active lipids involved in inflammatory processes. Increased levels of human nonpancreatic secretory phospholipase A2 (hnps-PLA2) have been detected in several pathological conditions. An inhibitor of this enzyme could have therapeutic utility. A broad screening program was carried out to identify chemical structures which could inhibit hnps-PLA2. One of the lead compounds generated by the screening program was 5-methoxy-2-methyl-1-(phenylmethyl)-1H-indole-3-acetic acid (13a). We describe the syntheses, structure--activity relationships, and pharmacological activities of a series of indole-3-acetamides and related compounds derived from this lead. This SAR was undertaken with the aid of X-ray crystal structures of complexes between the inhibitors and hnps-PLA2 which were of great value in directing the SAR.

The preceding papers of this series detail the development of functionalized indole-3-acetamides as inhibitors of hnps-PLA2. We describe here the extension of the structure-activity relationship to include a series of indole-3-glyoxamide derivatives. Functionalized indole-3-glyoxamides with an acidic substituent appended to the 4- or 5-position of the indole ring were prepared and tested as inhibitors of hnps-PLA2. It was found that the indole-3-glyoxamides with a 4-oxyacetic acid substituent had optimal inhibitory activity. These inhibitors exhibited an improvement in potency over the best of the indole-3-acetamides, and LY315920 (6m) was selected for evaluation clinically as an hnps-PLA2 inhibitor.

As reported in our previous paper, a series of indole-3-acetamides which possessed potency and selectivity as inhibitors of human nonpancreatic secretory phospholipase A2(hnps-PLA2) was developed. The design of these compounds was based on information derived from x-ray crystal structures determined for complexes between the enzyme and its inhibitors. We describe here the further implementation of this structure-based design strategy and continued SAR development to produce indole-3-acetamides with additional functionalities which provide increased interaction with important residues within the enzyme active site. These efforts led to inhibitors with substantially enhanced potency and selectivity.

The structure-activity relationship among a series of novel pyrazolidinone antibacterial agents is described. Specifically, the effect of modification of the side chain attached to the nitrogen at C-7 was explored in an attempt to improve the potency and spectrum of activity. This approach was successful in identifying several compounds having good in vitro profiles. These top candidates were then evaluated for their activity in vivo, and their pharmacokinetic behavior in various animal models was explored. This information proved critical for the identification of candidates for clinical evaluation.