PTPA and chronic myelogenous leukemia, BCR-ABL1 positive: FTY720 has been approved by the FDA for treatment of patients with refractory multiple sclerosis (Cohen et al, 2010) and has been shown to exert anti-cancer functions against CML (Neviani et al, 2007) and GISTs via activation of PP2A (Roberts et al, 2010) by an unknown mechanism.