Summary Cytokine storm during viral infection is a prospective predictor of morbidity and mortality, yet the cellular sources remain undefined. Here, using genetic and chemical tools to probe functions of the S1P1 receptor, we elucidate cellular and signaling mechanisms important in initiating cytokine storm. While S1P1 receptor is expressed on endothelial cells and lymphocytes within lung tissue, S1P1 agonism suppresses cytokines and innate immune cell recruitment in wild-type and lymphocyte deficient mice, identifying endothelial cells as central regulators of cytokine storm. Furthermore, our data reveal immune cell infiltration and cytokine production as distinct events both orchestrated by endothelial cells. Moreover, we demonstrate that suppression of early innate immune responses through S1P1 signaling results in reduced mortality during infection with a human pathogenic strain of influenza virus. Modulation of endothelium with a specific agonist suggests that diseases where amplification of cytokine storm is a significant pathological component could be chemically tractable.

BACKGROUND AND PURPOSESphingosine1-phosphate (S1P) receptors mediate multiple events including lymphocyte trafficking, cardiac function, and endothelial barrier integrity. Stimulation of S1P 1 receptors sequesters lymphocyte subsets in peripheral lymphoid organs, preventing their trafficking to inflamed tissue sites, modulating immunity. Targeting S1P receptors for treating autoimmune disease has been established in clinical studies with the non-selective S1P modulator, FTY720 (fingolimod, Gilenya ™ ). The purpose of this study was to assess RPC1063 for its therapeutic utility in autoimmune diseases. EXPERIMENTAL APPROACHThe specificity and potency of RPC1063 (ozanimod) was evaluated for all five S1P receptors, and its effect on cell surface S1P 1 receptor expression, was characterized in vitro. The oral pharmacokinetic (PK) parameters and pharmacodynamic effects were established in rodents, and its activity in three models of autoimmune disease (experimental autoimmune encephalitis, 2,4,6-trinitrobenzenesulfonic acid colitis and CD4 + CD45RB hi T cell adoptive transfer colitis) was assessed. KEY RESULTSRPC1063 was specific for S1P 1 and S1P 5 receptors, induced S1P 1 receptor internalization and induced a reversible reduction in circulating B and CCR7 + T lymphocytes in vivo. RPC1063 showed high oral bioavailability and volume of distribution, and a circulatory half-life that supports once daily dosing. Oral RPC1063 reduced inflammation and disease parameters in all three autoimmune disease models. CONCLUSIONS AND IMPLICATIONSS1P receptor selectivity, favourable PK properties and efficacy in three distinct disease models supports the clinical development of RPC1063 for the treatment of relapsing multiple sclerosis and inflammatory bowel disease, differentiates RPC1063 from other S1P receptor agonists, and could result in improved safety outcomes in the clinic.

The total syntheses of the potent glycosidase inhibitors castanospermine ((+)-1), 6-epicastanospermine ((+)-2), australine ((+)-3), and 3-epiaustraline ((+)-4) are described. The syntheses of indolizidine alkaloids (+)-1 and (+)-2 were accomplished in eight steps and in 18% and 24% overall yields from 2,5-dihydrofuran while the pyrrolizidine alkaloids (+)-3 and (+)-4 were obtained in a nine-step sequence in 17% and 22% overall yields from the same starting material. These four natural products are derived from a single common intermediate, nitroso acetal (−)-31, which is created in the key step by the asymmetric tandem [4 + 2]/[3 + 2] cycloaddition between silaketal nitro olefin 18 and chiral vinyl ether (+)-23. The ability to access both 5,5- and 5,6-fused bicyclic systems was a result of a successful in situ N-alkylation strategy during the hydrogenolysis of four highly functionalized nitroso acetals. A novel silaketal tether provided exceptional levels of diastereocontrol and the ideal combination of protection and functional-group placement for the tandem nitroalkene cycloaddition process.

A series of optically active 1,1Ј-binaphthalene-derived receptors with N-(pyridine-2,6-diyl)acetamide [CONH(py)] H-bonding sites in the 6,6Ј-positions has been prepared for the enantioselective complexation of the N-carbobenzyloxy (Cbz)-protected excitatory amino acids aspartic (Asp) and glutamic (Glu) acid via two COOH ؒ ؒ ؒ CONH(py) H-bonding arrays and additional secondary bonding interactions. The conformational homogeneity of the receptors is enhanced by locking the dihedral angle about the chirality axis through the C(1)᎐C(1Ј) bond of the 1,1Ј-binaphthalene moiety either by bridging the 2,2Јpositions or by attaching bulky substituents to these centres. Computer modelling has shown that bridging is more efficient in locking this dihedral angle than the introduction of bulky substituents, and these predictions have been confirmed by 1 H NMR binding studies in CDCl 3 and in CDCl 3 -CD 3 OD 99.8 : 0.2. Plots of the enantioselectivity ( GЊ) (difference in stability between diastereoisomeric complexes) in the recognition by the bridged receptors as a function of the enforced dihedral angle are peak-shaped, and the highest values have been measured in CDCl 3 (300 K) for the complexation of the enantiomers of N-Cbz-Asp [ ( GЊ) ‫؍‬ 6.9 kJ mol ؊1 ] and N-Cbz-Glu [ ( GЊ) ‫؍‬ 5.2 kJ mol ؊1 ] by (R)-21 ( ‫؍‬ 86 ± 4Њ). The more stable diastereoisomeric complexes are highly structured, and tight host-guest bonding has been confirmed by the observation of up to five intermolecular NOEs. Enforcing the conformational homogeneity by bridging represents a new general principle for improving the chiral recognition potential of 1,1Ј-binaphthalene receptors.

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