To elucidate whether ACKR3 antagonism is efficacious on established neuroinflammatory demyelinating diseases in a mouse strain that expresses both ligands for ACKR3, ACT-1004-1239 was first evaluated, in a therapeutic setting, in the proteolipid protein (PLP)-induced EAE model in SJL mice. Here, ACKR3 is linked to demyelinating disease.