Design and synthesis of a novel and potent series of inhibitors of cytosolic phospholipase A2 based on a 1,3-disubstituted propan-2-one skeleton

Using knowledge of the substrate specificity of cPLA(2) (phospliolipases A(2)), a novel series of inhibitors of this enzyme were designed based upon a three point model of inhibitor binding to the enzyme active site comprising a lipophilic anchor, an electrophilic serine "trap", and an acidic binding moiety. The resulting 1,3-diheteroatom-substituted propan-2-ones were evaluated as inhibitors of cPLA2 in both aggregated bilayer and soluble substrate assays. Systematic variation of the lipophilic, electrophilic, and acidic groups revealed a well-defined structure-activity relationship against the enzyme. Optimization of each group led to compound 22 (ARC70484XX), which contains a decyloxy lipophilic side chain, a 1,3-diaryloxypropan-2-one moiety as a unique serine trap, and a benzoic acid as the acidic binding group. AR-C70484XX was found to be among the most potent in vitro inhibitors of cPLA2, described to date being more than 20-fold more active against the isolated enzyme (IC50 = 0.03 muM) than the standard CPLA(2) inhibitor, arachidonyl trifluoromethyl ketone (AACOCF(3)), and also greater than 10-fold more active than AACOCF3 against the cellular production of arachidonic acid by HL60 cells (IC50 = 2.8 muM).