A series of 2-sulfonyl-pyrimidinyl derivatives was developed as apoptosis inhibitors. These represent the first class of apoptosis inhibitors that function through stabilizing mitochondrial respiratory complex II. Starting from a phenotypic screen hit with micromolar activity, we optimized the cellular apoptosis inhibition activity of 2-sulfonyl-pyrimidinyl derivatives to picomolar level (compound 42, also named as TC9-305). The therapeutic potential of these new apoptosis inhibitors was further demonstrated by their neuroprotective effect on an ischemic animal model.