A series of 2-oxoamides based on dipeptides and pseudodipeptides were synthesized and their activities towards two human intracellular phospholipases A2 (GIVA cPLA2 and GVIA iPLA2) and one human secretory phospholipase A2 (GV sPLA2) were evaluated. Derivatives containing a free carboxyl group are selective GIVA cPLA2 inhibitors. A derivative based on the ethyl ester of an ether pseudodipeptide is the first 2-oxoamide, which preferentially inhibits GVIA iPLA2. The effect of 2-oxoamides on the generation of arachidonic acid from RAW 264.7 macrophages was also studied and it was found that selective GIVA cPLA2 inhibitors preferentially inhibited cellular arachidonic acid release; one pseudodipeptide gave an IC50 value of 2 μM.

The phospholipase A2 (PLA2) superfamily hydrolyzes phospholipids to release free fatty acids and lysophospholipids, some of which can mediate inflammation and demyelination, hallmarks of the CNS autoimmune disease multiple sclerosis. The expression of two of the intracellular PLA2s (cPLA2 GIVA and iPLA2 GVIA) and two of the secreted PLA2s (sPLA2 GIIA and sPLA2 GV) are increased in different stages of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. We show using small molecule inhibitors, that cPLA2 GIVA plays a role in the onset, and iPLA2 GVIA in the onset and progression of EAE. We also show a potential role for sPLA2 in the later remission phase. These studies demonstrate that selective inhibition of iPLA2 can ameliorate disease progression when treatment is started before or after the onset of symptoms. The effects of these inhibitors on lesion burden, chemokine and cytokine expression as well as on the lipid profile provide insights into their potential modes of action. iPLA2 is also expressed by macrophages and other immune cells in multiple sclerosis lesions. Our results therefore suggest that iPLA2 might be an excellent target to block for the treatment of CNS autoimmune diseases, such as multiple sclerosis.