Ca 2+ -independent phospholipase A 2 (GVIA iPLA 2 ) has gained increasing interest recently as it has been recognized as a participant in biological processes underlying diabetes development and autoimmune-based neurological disorders. The development of potent GVIA iPLA 2 inhibitors is of great importance because only a few have been reported so far. We present a novel class of GVIA iPLA 2 inhibitors based on the β-lactone ring. This functionality in combination with a four-carbon chain carrying a phenyl group at position-3 and a linear propyl group at position-4 of the lactone ring confers excellent potency. trans-3-(4-Phenylbutyl)-4-propyloxetan-2-one (GK563) was identified as being the most potent GVIA iPLA 2 inhibitor ever reported (X I (50) 0.0000021, IC 50 1 nM) and also one that is 22 000 times more active against GVIA iPLA 2 than GIVA cPLA 2 . It was found to reduce β-cell apoptosis induced by proinflammatory cytokines, raising the possibility that it can be beneficial in countering autoimmune diseases, such as type 1 diabetes.