The FTY720 story.

The chemical 2-amino-2[2-(4-octylphenyl)ethyl]-1,3,propane diol is one of a class of small-molecule immunosuppressive agents. Better known as FTY720, this compound was chemically synthesized in an effort to minimize the toxic in vivo properties of a structurally related and highly potent immunosuppressive agent, myriocin. FTY720's mechanism of action, although not fully characterized, appears to be unique among immunosuppressants. Whereas the most well known biochemical characteristic of myriocin is its ability to inhibit serine palmitoyl transferase, the enzyme that initiates the biosynthetic pathway that leads to sphingosine, FTY720 is ineffective in this regard. In vivo, FTY720 induces a significant reduction in the number of circulating lymphocytes. It is thought to act by altering lymphocyte trafficking/homing patterns through modulation of cell surface adhesion receptors and ligands in a manner that has yet to be elucidated. Although much research has yet to be done to unravel the nature of the mechanism of action of FTY720, its efficacy has been sufficiently proven in numerous animal models, especially when administered in combination with cyclosporine. The agent is now progressing through human clinical trials, with the results of phase 1 clinical trials showing safety and tolerability in adult recipients of renal transplants. It is hoped that FTY720 will eventually prove to be an efficacious new weapon in the immunosuppressive armamentarium.