A cell-permeable pyrazolocarbohydrazide compound that acts as a potent, reversible, sphingosine competitive and ATP-non-competitive inhibitor of sphingosine kinase 1 (SphK1) activity with excellent selectivity over SphK2 (Ki = 1.33 and >> 25uM, respectively). Shown to suppress sphingosine-1-phosphate (S1P) production in A549 cells and efficiently induce apoptosis in several tumor cells (IC50 in the range of 0.1-1.8uM).