A labelled derivative of ISP-1 (myriocin), a fungal metabolite of the Chinese herb Iscaria sinclarii as well as a structural analogue of Sphingosine. It is a novel immune modulator that prolongs allograft transplant survival in numberour models by inhibiting lymphocyte emigration from lymphoid organs. Reported to be phosphorylated by sphingosine kinase to FTY720-P, which has been shown to potently stimulate GTPgS binding activity in S1P-transfected CHO cells (EC50 = 210 pM, 4.9 nM, 4.3 nM, and 1 nM for S1P1, S1P3, S1P4 and S1P5, respectively).