FTY720: early clinical experience.

FTY720 is the first in a new class of immunomodulators--sphingosine 1-phosphate receptor (S1P-R) agonists. It is highly effective in prolonging allograft survival in preclinical models of transplantation. Furthermore, FTY720 acts synergistically with calcineurin inhibitors and proliferation inhibitors in these models, suggesting that use of FTY720 in combination with classical immunosuppressants may be a promising new option for transplant patients. Phase I studies conducted in stable renal transplant patients maintained on a cyclosporine (CsA)-based regimen have revealed a tolerable profile of FTY720 for transplant pharmacotherapy. The pharmacokinetics of FTY720 is characterized by linear dose-proportional exposure over a wide range of doses, only moderate interpatient variability, and a prolonged elimination half-life (t(1/2) 89 to 157 hours). These factors suggest that FTY720 can be administered according to a simple once-daily schedule, without the need for blood-level monitoring or dose titration. The pharmacodynamics of FTY720 in humans are characterized by a significant reduction in peripheral blood count by up to 85%. In contrast to the nonspecific myelosuppressive effects of other immunosuppressants, this effect of FTY720 is specific for lymphocytes, with no effect observed on monocytes or granulocytes. In combination with CsA, FTY720 was well tolerated following single or multiple dosing, without any evidence of additional toxicities, indicating that FTY720 may be useful in the future design of more effective and less toxic regimens for prevention of graft rejection.