Sphingosine kinase (SphK) inhibitor. Isoenzyme-selective for SphK1; displays no activity at SphK2. Also displays no inhibitory activity against a range of protein kinases including PKC, PKA, ERK1, EGFR and CDK2. Exhibits potent antileukemic activity in vivo; inhibits the growth of both U937 and Jurkat T cells. Also suppresses proliferation and induces apoptosis in several human glioblastoma cell lines.