Moderately potent, selective S1P(1) receptor agonists identified from high-throughput screening have been adapted into lipophilic tails for a class of orally bioavailable amino acid-based S1P(1) agonists represented by 7. Many of the new compounds are potent S1P(1) agonists that select against the S1P(2), S1P(3), and S1P(4) (although not S1P(5)) receptor subtypes. Analogues 18 and 24 are highly orally bioavailable and possess excellent pharmacokinetic profiles in the rat, dog, and rhesus monkey.

FTY720 is an immunosuppressive agent that modulates lymphocyte trafficking. It is phosphorylated in vivo to FTY720-phosphate (FTY-P) and binds to a family of G protein-coupled receptors recognizing sphingosine 1-phosphate (S1P) as the natural ligand. It has previously been reported that FTY-P blocks egress of lymphocytes from the thymus and lymph nodes, resulting in peripheral blood lymphopenia. We now report that FTY-P also causes displacement of marginal zone (MZ) B cells to the splenic follicles, an effect that is similar to that observed after in vivo administration of lipopolysaccharide. This effect is specific to B cells in the MZ, as treatment with FTY-P does not cause redistribution of the resident macrophage population. A small but statistically significant decrease in the expression of beta1 integrin on MZ B cells was observed with FTY-P treatment. The redistribution of MZ B cells from the MZ sinuses does not abolish the ability of these cells to respond to the T-independent antigen, trinitrophenol-Ficoll. It has been proposed that the displacement of MZ B cells to the follicles is an indication of cell activation. Consistent with this, FTY-P caused an increase in percentage of MZ B cells expressing activation markers CD9, CD1d, and CD24. These results suggest that S1P receptors on MZ B cells are responsible for their mobilization to follicles.

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