Fingolimod-d4 (hydrochloride) is the deuterium labeled Fingolimod hydrochloride. Fingolimod hydrochloride (FTY720) is a sphingosine 1-phosphate (S1P) antagonist with an IC50 of 0.033 nM in K562 and NK cells. Fingolimod hydrochloride (FTY720) also is a pak1 activator, a immunosuppressant[1].