RP101988, the major active metabolite of Ozanimod, is a selective, potent S1PR1 (sphingosine-1-phosphate receptor 1) agonist, with EC50s of 0.19 nM and 32.8 nM for S1PR1 and S1PR5, respectivlely.In Vitro: RP101988 is a substrate of P-gp and breast cancer resistance protein (BCRP) drug transporters[2].