Potent inhibitors of lipoprotein-associated phospholipase A2: Benzaldehyde O-heterocycle-4-carbonyloxime

A series of multi-substituted oximes were prepared and their potencies for inhibiting lipoprotein-associated phospholipase A2 (Lp-PLA2) activity were evaluated in vitro. Among them, compounds 3a, 3b, and 3m were identified to display a micromolar potency for inhibiting Lp-PLA2 in whole human plasma and isolated human LDL. Based on these results, structure–activity relationship was studied on modification of three parts of R1, R2, and R3 to identify a potent pharmacophore for Lp-PLA2. In an attempt to introduce various functional groups at R2 and R3, we discovered that replacement of less lipophilic groups led to an increase of inhibitory activity. Among the tested oxime derivatives, cyano- and morpholino-substituted analogue 4f at R2 and R3 had the highest potency with an IC50 value of 0.05 μM in whole human plasma.