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.

Compound 2 (0.2 µ ) was mixed with 150 µ of i-AmOAc and ozonized, 1 mg of powdered Ph3P was added, and the mixture was shaken. When the solution reached room temperature a 0.4-µ1 aliquot was analyzed under the same glc conditions as above except that the final temperature control was set at 165°instead of 150°. The products formed, EtCHO and 6-hydroxyhexanal, emerged in 2.9 and 29.5 min, respectively. Synthesis of 1. (£>6-Nonenoic acid,11 bp 95-102°(0.4 mm), zt35D 1.4462, was converted to 1 by refluxing for 4 hr a solution of 30 g of the acid and 4 drops of concentrated HC1 in 100 ml of CH3OH, removing the latter under reduced pressure, dissolving the residue in EtaO, and washing with cold 10% NaHC03 solution followed by cold HaO. Distillation of the dried solution gave 29.2 g (89%) of colorless liquid, bp 105-107°(10 mm), n,sD 1.4345.

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.

A series of (substituted amino)-1,2,4-benzothiadiazine 1-oxides has been synthesized and most members of the series have been shown to have blood pressure lowering effects in normotensive rabbits and in spontaneously hypertensive rats. The most active member of the series was 3-[4-(2-furoyl)-1-piperazinyl]-6,7-dimethoxy-1-methyl-1H-1,2,4-benzothiadiazine 1-oxide hydrochloride. This compound in animal tests was equipotent to the known antihypertensive Prazosin.