Fingolimod: A Review of Its Use in Relapsing-Remitting Multiple Sclerosis

Sphingosine 1-phosphate (S1P), a lysophospholipid, has gained relevance to multiple sclerosis through the discovery of FTY720 (fingolimod), recently approved as an oral treatment for relapsing forms of multiple sclerosis. Its mechanism of action is thought to be immunological through an active phosphorylated metabolite, FTY720-P, that resembles S1P and alters lymphocyte trafficking through receptor subtype S1P(1). However, previously reported expression and in vitro studies of S1P receptors suggested that direct CNS effects of FTY720 might theoretically occur through receptor modulation on neurons and glia. To identify CNS cells functionally contributing to FTY720 activity, genetic approaches were combined with cellular and molecular analyses. These studies relied on the functional assessment, based on clinical score, of conditional null mouse mutants lacking S1P(1) in CNS cell lineages and challenged by experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. All conditional null mutants displayed WT lymphocyte trafficking that responded normally to FTY720. In marked contrast, EAE was attenuated and FTY720 efficacy was lost in CNS mutants lacking S1P(1) on GFAP-expressing astrocytes but not on neurons. In situ hybridization studies confirmed that astrocyte loss of S1P(1) was the key alteration in functionally affected mutants. Reductions in EAE clinical scores were paralleled by reductions in demyelination, axonal loss, and astrogliosis. Receptor rescue and pharmacological experiments supported the loss of S1P(1) on astrocytes through functional antagonism by FTY720-P as a primary FTY720 mechanism. These data identify nonimmunological CNS mechanisms of FTY720 efficacy and implicate S1P signaling pathways within the CNS as targets for multiple sclerosis therapies.

This article represents a planned regular updating of the previous British Association of Dermatologists guidelines for the management of basal cell carcinoma. These guidelines present evidence-based guidance for treatment, with identification of the strength of evidence available at the time of preparation of the guidelines, and a brief overview of epidemiological aspects, diagnosis and investigation.

The oral immunomodulator FTY720 has shown efficacy in patients with relapsing multiple sclerosis (MS). FTY720 functionally antagonizes sphingosine 1-phosphate receptor-1 (S1P1) on T cells and consequently inhibits S1P/S1P1-dependent lymphocyte egress from secondary lymphoid organs. Little is known about the phenotype and function of T cells remaining in peripheral blood during long-term FTY720 treatment. T cells from FTY720-treated, interferon-beta (IFNbeta)-treated and untreated patients with MS, and healthy donors (HD) were analyzed with respect to T cell subpopulation composition, proliferation, and cytokine production. In FTY720-treated patients (n = 16), peripheral blood CD4+ and CD8+ T cell counts were reduced by approximately 80% and 60% when compared to the other groups (IFN beta: n = 7; untreated: n = 5; HD: n = 10). This related to selective reduction of naive (CCR7+CD45RA+) and central memory (CCR7+CD45RA-) T cells (TCM), and resulted in a relative increase of peripheral effector memory (CCR7-CD45RA- [TEM] and CCR7-CD45RA+ [TEMRA]) T cells. The remaining blood T cell populations displayed a reduced potential to secrete IL-2 and to proliferate in vitro, but rapidly produced interferon-gamma upon reactivation, confirming a functional TEM/TEMRA phenotype. Neither FTY720 nor FTY720-P directly suppressed proliferation or cytokine production by T cells. Therapeutic dosing of FTY720 reduces naïve T cells and TCM, but not TEM, in blood, without affecting T cell function. This is presumably because naive T cells and TCM express the homing receptor CCR7, allowing recirculation to secondary lymphoid tissues on a regular basis and, thus, trapping of the cells by FTY720 in lymph nodes.