FilgotinibisapotentandselectiveJAK1inhibitor.ItisconsideredapromisingagentasitinhibitsJAK1selectively.Filgotinibdisplayedaselectivityof30-foldforChemicalbookJAK1-overJAK2-dependentsignaling.GLPG0634dose-dependentlyinhibitedTh1andTh2differentiationandtoalesserextentthedifferentiationofTh17cellsinvitro.