**5.1.3 Depletion of extracellular S1P with S1P antibody**

Specific antibodies against S1P have been developed and are currently being tested in clinical studies for the treatment of cancer, fibrosis, inflammation, macular degeneration, diabetic retinopathy, glaucoma, and other diseases (Graler and Goetzl, 2004). The antibodies are thought to bind S1P and reduce the extracellular pool of bioactive S1P (Sabbadini, 2006). Indeed, a preclinical study using blocking S1P antibodies to prevent tumor progression was recently reported (Visentin et al., 2006). In this hallmark study, a specific monoclonal antibody recognizing S1P was administered to mice harboring human cancer xenografts. The intervention reduced, and in some cases completely eliminated, tumour formation and accompanying tumour angiogenesis. The results suggest that antibody-mediated inhibition of S1P signalling may be developed as a strategy for inhibiting pannus formation and angiogenesis in RA.
