Full Pharmacological Efficacy of a Novel S1P₁ Agonist That Does Not Require S1P-Like Headgroup Interactions

Abstract

Strong evidence exists for interactions of zwitterionic phosphate and amine groups in sphingosine-1 phosphate (S1P) to conserved Arg and Glu residues present at the extracellular face of the third transmembrane domain of S1P receptors. The contribution of Arg 120 and Glu 121 for high-affinity ligand-receptor interactions is essential, because single-point R 120A or E 121 A S1P 1 mutants neither bind S1P nor transduce S1P function. Because S1P receptors are therapeutically interesting, identifying potent selective agonists with different binding modes and in vivo efficacy is of pharmacological importance. Here we describe a modestly water-soluble highly selective S1P 1 agonist [2-(4-(5-(3,4-diethoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl amino) ethanol (CYM-5442)] that does not require Arg 120 or Glu 121 residues for activating S1P 1 -dependent p42/p44 mitogen-activated protein kinase phosphorylation, which defines a new hydrophobic pocket in S1P 1 . CYM-5442 is a full agonist in vitro for S1P 1 internalization, phosphorylation, and ubiquitination. It is noteworthy that CYM-5442 was a full agonist for induction and maintenance of S1P 1 -dependent blood lymphopenia, decreasing B lymphocytes by 65% and T lymphocytes by 85% of vehicle. Induction of CYM-5442 lymphopenia was dose-and time-dependent, requiring serum concentrations in the 50 nM range. In vitro measures of S1P 1 activation by CYM-5442 were noncompetitively inhibited by a specific S1P 1 antagonist [(R)-3-amino-(3-hexylphenylamino)-4-oxobutylphosphonic acid (W146)], competitive for S1P, 2-amino-2-(4-octylphenethyl)propane-1,3-diol (FTY720-P), and 5-[4-phenyl-5-(trifluoromethyl)-2-thienyl]-3-[3-(trifluoromethyl)phenyl]-1,2, 4-oxadiazole (SEW2871). In addition, lymphopenia induced by CYM-5442 was reversed by W146 administration or upon pharmacokinetic agonist clearance. Pharmacokinetics in mice also indicated that CYM-5442 partitions significantly in central nervous tissue. These data show that CYM-5442 activates S1P 1 -dependent pathways in vitro and to levels of full efficacy in vivo through a hydrophobic pocket separate from the orthosteric site of S1P binding that is headgroup-dependent.

Selective Sphingosine-1-Phosphate Receptor 1 Modulation Attenuates Experimental Intracerebral Hemorrhage

“…Of note, the beneficial effect of RP101075 on neurological outcomes and brain edema was blocked by W146, a selective RP101075 antagonist. [38][39][40] Together with the reduced cellular infiltration and inflammatory cytokine expression after RP101075 treatment, these results support the notion that modulation of S1PR1 is sufficient to suppress brain inflammation and provide protection in ICH. The superior pharmacological features along with its efficacy may qualify RP101075 as a promising candidate for future ICH investigations.…”

Host endothelial S1PR1 regulation of vascular permeability modulates tumor growth

“…The efficiency of long-term continuous delivery of the implanted microdialysis pumps in each mouse was validated at the end of each experiment by determining drug serum levels using LC-MS as described previously (19). Mice were excluded from the study when LC-MS drug plasma levels were more than 2 SD less than the mean, which was interpreted as pump failure.…”

Engagement of S1P1-degradative mechanisms leads to vascular leak in mice

“…The S1P 1 -specific receptor modulator AUY954, a potent functional antagonist that induces receptor downregulation (31), also caused receptor degradation in the lung tissue and induced potent vascular permeability ( Figure 5, C and D). In addition, W146, a competitive antagonist of S1P 1 (32), induced vascular permeability at early time points, even though it did not induce substantial receptor degradation. These results suggest that S1P 1 antagonism or degradation is responsible for increased vascular permeability in vivo.…”