S1PR1 and myeloid sarcoma: Phosphorylated fingolimod acts as a functional antagonist of S1PR1 expressed on lymphocytes, sequestering these cells in lymph nodes and preventing them from infiltrating the CNS, which is one of the mechanisms of action by which it ameliorates the symptoms of MS (Brinkmann et al., 2010; Ntranos et al., 2014).