Purity >98%. FTY720 is a novel immune modulator that prolongs allograft transplant survival in numerous models by inhibiting lymphocyte emigration from lymphoid organs. FTY720 is phosphorylated by sphingosine kinases in vivo, and then acts as a potent agonist at four of the five sphingosine-1-phosphate (S1P) receptors. FTY720 (R)-phosphate is one of the stereoisomers of FTY720-phosphate, but it is apparently not formed in vivo . FTY720 (S)-phosphate exhibits Ki values of 2.1, 5.9, 23, and 2.2 nM for S1P1,3,4,5, respectively, whereas the R isomer binds with 5 to130-fold lower affinity.