Purity >90%. GW 4869 is a cell-permeable, non-competitive inhibitor of neutral sphingomyelinases (IC50 = 1 MM), but does not affect acid sphingomyelinase activity. It inhibits TNF-a-mediated sphingomyelin hydrolysis (100% inhibition at 20 MM) and TNF-a-induced cell death in MCF7 cells without interfering with activation of NF- Kappa B or glutathione depletion in response to TNF.