Sphingosine Kinase Inhibitor (SKI-II)

2-(p-Hydroxyanilino)-4-(p-chlorophenyl)thiazole (SK1-II) is a cell permeable, potent, and specific inhibitor of sphingosine kinase (IC₅₀ = 0.5 μM). The compound does not bind to the ATP-binding site and does not affect the kinase activities of hERK2, hPI3K, or hPKCα at concentrations up to 60 μM. SK1-II showed anti-tumor properties, inducing apoptosis in a number of cell lines including those that express Pgp or MRP1 drug-transport proteins.