Discovery of BAF312 (Siponimod), a potent and selective S1P receptor modulator

Article abstract of DOI:10.1021/ml300396r

A novel series of alkoxyimino derivatives as S1P₁ agonists were discovered through de novo design using FTY720 as the chemical starting point. Extensive structure-activity relationship studies led to the discovery of (E)-1-(4-(1-(((4-cyclohexyl-3-(trifluoromethyl)benzyl)oxy)imino)ethyl) -2-ethylbenzyl)azetidine-3-carboxylic acid (32, BAF312, Siponimod), which has recently completed phase 2 clinical trials in patients with relapsing-remitting multiple sclerosis.

Full text of DOI:10.1021/ml300396r

Letter
pubs.acs.org/acsmedchemlett
Discovery of BAF312 (Siponimod), a Potent and Selective S1P
Receptor Modulator
Shifeng Pan,*,† Nathanael S. Gray,† Wenqi Gao,† Yuan Mi,† Yi Fan,† Xing Wang,† Tove Tuntland,†
Jianwei Che,† Sophie Lefebvre,† Yu Chen,† Alan Chu,† Klaus Hinterding,‡ Anne Gardin,‡ Peter End,‡
Peter Heining,‡ Christian Bruns,‡ Nigel G. Cooke,‡ and Barbara Nuesslein-Hildesheim‡
†Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
‡Novartis Institute for Biomedical Research, Novartis Campus, CH-4056 Basel, Switzerland
S
* Supporting Information
ABSTRACT: A novel series of alkoxyimino derivatives as S1P1 agonists were discovered
through de novo design using FTY720 as the chemical starting point. Extensive structure−
activity relationship studies led to the discovery of (E)-1-(4-(1-(((4-cyclohexyl-3-
(trifluoromethyl)benzyl)oxy)imino)ethyl)-2-ethylbenzyl)azetidine-3-carboxylic acid (32,
BAF312, Siponimod), which has recently completed phase 2 clinical trials in patients
with relapsing−remitting multiple sclerosis.
KEYWORDS: S1P receptor, S1P1 agonist, lymphocytes
phingosine-1-phosphate (S1P) is a bioactive sphingolipid
myocytes and bradycardia in healthy volunteers.20 In the same
Sthat regulates a diverse range of physiological processes report, we presented the in vitro profile of BAF312, including
its effects on S1P1 receptor internalization as well as its
preclinical efficacy in a rat experimental autoimmune
encephalomyelitis (EAE) model. Herein, we report our
medicinal chemistry efforts that culminated in the discovery
of (E)-1-(4-(1-(((4-cyclohexyl-3-(trifluoromethyl)benzyl)oxy)-
imino)ethyl)-2-ethylbenzyl)azetidine-3-carboxylic acid 32
(BAF312, Siponimod), a potent S1P3-sparing S1P1 agonist
currently undergoing clinical trials in patients with multiple
sclerosis.
One focus of our initial efforts was to develop FTY720
analogues that could (1) achieve selectivity against S1P3 and
(2) reduce in vivo elimination half-life. We envisioned that
modifications providing increased rigidity in the lipophilic alkyl
chain of FTY720 may lead to S1P receptor subtype selectivity.
One of the approaches led to the discovery of analogues
containing substituted benzyloxy oximes that replace the n-
octyl moiety, as exemplified in compound 1 (Figure 1). When
dosed orally to mice, compound 1 was equally efficacious as
FTY720 in inducing lymphocyte redistribution. However, the
in vivo elimination half-life of the corresponding phosphate
remained very long (t1/2 > 30 h), and the volume of distribution
was large (Vss = 36.9 L/kg). One possible explanation for this
pharmacokinetic behavior is that the charged phosphate moiety,
which is generated in vivo, contributes to high nonspecific
binding to lipoproteins in tissues. We decided to explore
replacing the phosphate moiety with a carboxylic acid, which
might reduce nonspecific binding and thereby reduce the
volume of distribution and elimination half-life. An additional
such as lymphocyte trafficking, cardiac function, vascular
development, and inflammation.1−4 S1P mediates these
functions primarily through its interaction with five G-
5,6
protein-coupled receptors known as S1P1−5
.
The S1P-
mediated signaling has become the focus of intense research
during the past decade, partly inspired by the therapeutic
development of FTY720 (fingolimod) (Figure 1), which was
recently approved as the first oral drug for relapsing−remitting
multiple sclerosis.7 FTY720 effectively inhibits the lymphocyte
egress from the thymus and lymph nodes and thereby leads to
redistribution of lymphocytes away from peripheral inflamma-
tory tissues.7 FTY720 is phosphorylated in vivo by sphingosine
kinase to the active metabolite FTY720-phosphate (Figure
1).8,9 The latter binds with nanomolar affinity as an agonist at
four of the five S1P receptors, namely, S1P1, S1P3, S1P4, and
S1P5.8,9 Interestingly, FTY720-phosphate was shown to elicit its
immunosuppressive effect through functionally antagonizing
S1P1 signaling pathway.10,11 It induces rapid and persistent
internalization of the S1P1 receptor that is required for
lymphocyte egress from the secondary lymphoid organs.
A transient, dose-dependent decrease of heart rate was
observed with FTY720 in clinical studies.12 The S1P3 receptor
is thought to be responsible for the bradycardia, based on the
lack of S1P-induced heart rate reduction in S1P3 knockout
mice.13,14 S1P3 agonism is also known to be associated with
vaso- and bronchoconstriction and pulmonary epithelial
leakage.15 Numerous research groups have been working
toward discovering S1P3-sparing S1P1 agonists.16−19 However,
our recent report suggested species-dependent bradycardia and
a dominant role of S1P1 in mediating heart rate in humans, as
the treatment with BAF312, a dual S1P1,5 agonist sparing S1P3
activity, caused GIRK channel activation in human atrial
Received: November 15, 2012
Accepted: January 4, 2013
© XXXX American Chemical Society
A
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ACS Medicinal Chemistry Letters
Letter
Figure 1. Structures of FTY720, FTY720-phosphate, and their analogues.
Figure 2. Amino carboxylate to mimic amino phosphate.
advantage of pursuing a nonpro-drug strategy is that we
eliminated the complication of understanding two overlapping
structure−activity relationships (SAR), namely, the SAR of the
sphingosine kinase, whose action is required to generate the
bioactive aminophosphate, and the SAR of the resulting
aminophosphate for the S1P-receptor family. To efficiently
identify an optimal amino carboxylate group, we utilized a
reductive amination strategy whereby an aldehyde fragment
corresponding to the “hydrophobic tail” of compound 1 could
be efficiently derivatized with a collection of amino carboxylic
acids (Figure 2). From this effort, compound 2 was identified as
one of the most potent compounds with an EC50 value of 300
nM at the S1P1 receptor subtype in a GTPγS binding assay.21
This compound was then used as a new lead for further
optimization.
We first turned our attention to the substitutions on the
phenyl rings A and B (see Figure 2). The key SAR results for
select analogues within this series are summarized in Table 1.
On ring A, substitution at the 2-position is well tolerated. Both
2-fluoro 4 and 2-trifluoromethyl 6 show increased agonism in
comparison to compound 2. Especially the latter reaches single
digit nanomolar potency. In contrast, the 1-position is less
preferred for substitution. 1-Fluoro 3 is 2-fold less potent than
its corresponding 2-fluoro analogue 4, while 1-trifluoromethyl 5
shows very low activity at 10 μM. Substitutions on ring B
(compounds 7−12) are in general less tolerated than those on
ring A. Additional substitutions of ring B (compounds 13−16)
fail to further increase the potency of compound 6.
Table 1. S1P1 Potencies with Different Biphenyl Substituents
a
compd
R1
R2
S1P1 EC50 (μM)
2
3
H
H
H
H
H
H
0.3
0.12
0.061
10
1-F
4
2-F
5
1-CF3
2-CF3
H
6
0.009
0.21
0.64
1.5
7
3′-F
8
H
3′-Me
3′-OMe
1′-OMe
3′-CF3
1′-CF3
1′-F
3′-F
3′-Me
2′-F-3′-F
9
H
10
11
12
13
14
15
16
H
1.4
H
10
H
1.7
2-CF3
2-CF3
2-CF3
2-CF3
0.008
0.011
0.094
0.016
a
GTPγS binding assay (see ref 21 for detailed assay descriptions).
molecular modeling based upon the recently solved S1P1
crystal structure (PDB code: 3V2Y).22 The predicted binding
mode of compound 2 is illustrated in Figure 3. The ligand
Although these chemistry efforts were not informed by
molecular modeling, they can now be rationalized using
B
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ACS Medicinal Chemistry Letters
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Table 2. Structure−Activity Relationship of the Terminal
Hydrophobic Groups
a
EC50 (μM)
compd
R
S1P1
S1P3
17
18
19
20
2-furanyl
0.015
3.0
5.9
1.6
1.5
2-thienyl
0.018
cyclopentyl
cyclohexyl
0.0006
0.0003
a
GTPγS binding assay (see ref 21 for detailed assay descriptions).
After successfully optimizing the hydrophobic tail to reach
subnanomolar potency, we then turned our attention to the
phenyl ring C and the hydrophilic head groups. The SAR of
select compounds is summarized in Table 3. Replacing phenyl
Table 3. Structure−Activity Relationship of the Head
Groups
Figure 3. Binding mode of compound 2 in S1P1. The electrostatic
surface is color coded: blue is positively charged, red is negatively
charged, and green is hydrophobic.
binding pocket of S1P1 consists of a charged entrance and a
large enclosed hydrophobic cavity. The carboxylic acid
headgroup forms salt bridges with Lys34 and Arg120 and a
hydrogen bond with Tyr29. In addition, the charged amine
group forms a salt bridge with Glu121. Therefore, the polar
headgroup involves multiple strong electrostatic interactions
that anchor the ligand molecule in the binding site. The
hydrophobic tail (i.e., biphenyl moiety) is predicted to fit nicely
into the large hydrophobic cavity. On the basis of the binding
mode, 2-F substitution (compound 4) adds additional
hydrophobic interaction relative to compound 2 and leads to
an increase in potency. In contrast, the fluorine at the 1-
position in compound 3 does not interact with the protein
residue as tightly as at the 2-position, and this is consistent with
the observed SAR. A bulkier trifluoromethyl group at the 1-
position in compound 5 introduces a potential steric clash with
the receptor that leads to much reduced activity. The same
group substituted at the 2-position in compound 6, however,
engages improved nonpolar interactions with Leu276 and
Leu272. In addition, it forces the terminal phenyl ring into near
perpendicular position, which results into better van der Waals
interactions at this orientation. As the terminal phenyl group is
at the bottom of the hydrophobic pocket, substitutions at this
ring are much less tolerated (compounds 7−12).
To further optimize the interaction with the hydrophobic
pocket that is tightly occupied by phenyl ring B, we explored
several phenyl replacements as summarized in Table 2.
Compounds containing five-membered heterocycles such as
2-furanyl 17 or 2-thienyl 18 showed comparable activity to the
corresponding phenyl analogue 6. To our delight, the
replacement of the phenyl moiety by either a cyclopentyl 19
or a cyclohexyl 20 group resulted into a greater than 10-fold
increase in potency, while it had only marginal impact on the
S1P3 activity.
a
EC50 (μM)
compd
R1
R2
XY
S1P1
S1P3
21
22
23
24
25
26
27
28
29
30
31
32
A
A
A
A
A
A
A
A
A
A
B
B
H
H
H
H
F
NCH
CHN
S
0.0026 (86)
0.0014 (92)
0.0022 (104)
0.017 (100)
0.0003 (105)
0.0006 (106)
0.0004 (85)
0.002 (94)
4.3 (44)
2.6 (53)
4.0 (79)
2.5 (62)
2.2 (61)
1.9 (50)
1.1 (65)
5.9 (159)
7.2 (43)
1.3 (63)
3.2 (127)
5.0 (55)
O
CHCH
CHCH
CHCH
CHCH
CHCH
CHCH
CHCH
CHCH
Cl
Br
Me
Et
0.0007 (92)
0.0004 (98)
0.0016 (80)
0.0004 (91)
cyclo-Pr
Me
Et
a
GTPγS binding assay (see ref 21 for detailed assay descriptions);
values in parentheses represent the Emax, % of agonism at 10 μM as
compared to S1P.
ring C by heterocyles, such as pyridines 21 and 22 or a
thiophene 23, only led to marginal decreases in S1P1 activity
while maintaining good selectivity against S1P3. However, the
furanyl analogue 24 showed significant loss of activity (>20-
fold) presumably due to the smaller ring size that leads to an
increased dihedral angle between the head and the tail groups.
Because there was no clear improvement in potency or
selectivity achieved by these modifications, we next examined
the effects of substitutions on the phenyl ring. Substitutions at
the R2 position with halogens (compounds 25−27) or small
alkyl groups (compounds 28−30) are very well tolerated with
comparable activity to the phenyl analogue 20. Interestingly, a
methyl group (28) or an ethyl group (29) leads to weaker
activity on S1P3. As the azetidine carboxylic acid group showed
C
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ACS Medicinal Chemistry Letters
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comparable activity to the β-alanine analogue in our survey
summarized in Figure 2, we re-evaluated this headgroup with
the optimized lipophilic moieties with compounds 31 and 32.
Both compounds showed comparable activity and selectivity.
On the basis of favorable potency, selectivity, and other
druglike properties, compound 32 was chosen for further in
vitro and in vivo testing. Compound 32 is extensively bound to
rat, dog, monkey, and human plasma proteins (>99.9%). It
shows high and passive permeability in a Caco-2 human cell
permeability assay with no transporter-mediated efflux observed
at the test concentrations of 0.5−50 μM. In vitro metabolism
studies with liver microsomes indicate that the metabolic
clearance of compound 32 is low in mouse and dog
microsomes, low to moderate in monkey and human, but
high in rat. In the rat, the fraction of the dose absorbed is 58%,
which is calculated from the total amount of metabolites
detected in feces and urine. The absolute bioavailability is 50
and 71% in the rat and monkey, respectively, indicating no
major presystemic first pass metabolism. Consistent with the
low metabolic clearance in vitro, the systemic clearance (CL) is
low in both rat and monkey relative to respective hepatic blood
flow (Table 4). The terminal half-life is approximately 6 and 19
For S1P1 agonists, the reduction of peripheral lymphocyte
count has been used as a pharmacodynamic biomarker for
efficacy in autoimmune diseases. On the basis of the favorable
PK profile, compound 32 was evaluated in an in vivo PK/PD
model in Lewis rats, where lymphocyte count is measured in
blood at different time points. At a dose of 1 mg/kg per oral,
the rapid increase in the systemic compound concentration
coincides with a marked decrease in peripheral lymphocyte
counts as illustrated in Figure 4. At the Tmax of 8 h
postadministration, the lymphocyte counts were decreased by
88%. In contrast to FTY720, after 48 h, the peripheral
lymphocyte counts returned to normal levels in animals treated
with compound 32 accompanying compound elimination from
the systemic circulation, suggesting it has a shorter duration of
action than FTY720. As determined in a separate experiment,
the effective dose for achieving 50% reduction of peripheral
lymphocyte counts at the 6 h time point postdose was 0.14 mg/
kg.
In cardiac repolarization assays (hERG patch clamp),
compound 32 showed minimal inhibition of less than 10% at
25 μM. It did not exhibit genotoxic potential in the standard
battery of in vitro and in vivo tests. Its selectivity was evaluated
by screening against a large panel of receptors, ion channels,
transporters, and kinases. No appreciable activities at
concentrations below 1 μM were identified, suggesting a low
potential for off-target effects. This was also confirmed by the
absence of unexpected adverse findings in the toxicology
studies performed.
Table 4. In Vivo Pharmacokinetics in Preclinical Species
mean SD
CL (L/h/kg)
Vss (L/kg)
T1/2 (h)
1.3
19 0.5
F (%)
rat
0.36 0.023
0.098 0.9
2.15 0.311
2.12 0.12
6
50
71
monkey
h in rat and monkey, respectively, and therefore is considerably
shorter than those of FTY720 and FTY720-phosphate.
Compound 32 is moderately distributed to tissues as compared
to total body water following intravenous administration to rat
(Vss = 2.15 0.31 L/kg) and monkey (Vss = 2.12 0.12 L/
kg). On the basis of the ratio of metabolites versus parent
compound detected in feces and urine, oxidative metabolism is
determined as the predominant mechanism of elimination for
compound 32 in rat after intravenous and oral administration.
Direct renal excretion of compound 32 is not observed in the
rat.
In summary, a novel chemical series was developed using
FTY720 as an initial lead structure. Compounds were
optimized for potency at S1P1, selectivity against S1P3, safety,
and pharmacokinetics. This led to the discovery of the clinical
candidate 32 (BAF312, Siponimod). Treatment with com-
pound 32 in Lewis rats led to a dose-dependent reduction of
peripheral lymphocyte counts that rapidly returned to normal
levels upon compound clearance from systemic circulation.
This compound is now in late-stage clinical trials in patients
with multiple sclerosis.
Figure 4. PK/PD relationship of compound 32 after oral administration of 1 mg/kg to Lewis rats (n = 3).
D
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respectively, regulate lymphocyte recirculation and heart rate. J. Biol.
Chem. 2004, 279, 13839−13848.
ASSOCIATED CONTENT
■
S
* Supporting Information
(15) Murakami, A.; Takasugi, H.; Ohnuma, S.; Koide, Y.; Sakurai, A.;
Takeda, S.; Hasegawa, T.; Sasamori, J.; Konno, T.; Kayashi, K.;
Watanabe, Y.; Mori, K.; Sato, Y.; Takahashi, A.; Mochizuki, N.;
Takakura, N. Sphingosine 1-phosphate (S1P) regulates vascular
contraction via S1P3 receptor: investigation based on a new S1P3
receptor antagonist. Mol. Pharmacol. 2010, 77, 704−713.
General scheme and analytical data of compounds 2−31;
synthetic scheme, procedure, and analytical data for compound
32; and experimental procedure for PK/PD studies of 32. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(16) For recent examples: Harrington, P. E.; Croghan, M. D.; Fotsch,
C.; Frohn, M.; Lanman, B. A.; Penninton, L. D.; Pickrell, A. J.; Reed,
A. B.; Sham, K. K. C.; Tasker, A.; Arnett, H. A.; Fiorino, M.; Lee, M.
R.; McElvain, M.; Morrison, H. G.; Xu, H.; Xu, Y.; Zhang, X.; Wong,
M.; Cee, V. J. Optimization of a potent, orally active S1P1 agonist
containing a quinolinone core. ACS Med. Chem. Lett. 2012, 3, 74−78.
(17) Ren, F.; Deng, G.; Wang, H.; Luan, L.; Meng, Q.; Xu, Q.; Xu,
H.; Xu, X.; Zhang, H.; Zhao, B.; Li, C.; Guo, T. B.; Yang, J.; Zhang,
W.; Zhao, Y.; Jia, Q.; Lu, H.; Xiang, J.-N.; Elliott, J. D.; Lin, X.
Discovery of novel 1,2,4-thiadiazole derivatives as potent, orally active
agonists of sphingosine 1-phosphate receptor subtype 1 (S1P1). J. Med.
Chem. 2012, 55, 4286−4296.
(18) Buzard, D. J.; Han, S.; Lopez, L.; Kawasaki, A.; Moody, J.;
Thoresen, L.; Ullman, B.; Lehmann, J.; Calderon, I.; Zhu, X.;
Gharbaoui, T.; Sengupta, D.; Krishnan, A.; Gao, Y.; Edwards, J.;
Barden, J.; Morgan, M.; Usmani, K.; Chen, C.; Sadeque, A.; Thatte, J.;
Solomon, M.; Fu, L.; Whelan, K.; Liu, L.; Al-Shamma, H.; Gatlin, J.;
Le, M.; Xing, C.; Espinola, S.; Jones, B. M. Fused tricyclic indoles as
S1P1 agonists with robust efficacy in animal models of autoimmune
disease. Bioorg. Med. Chem. Lett. 2012, 22, 4404−4409.
AUTHOR INFORMATION
■
Corresponding Author
*Tel: 858-812-1621. E-mail: span@gnf.org.
Notes
The authors declare no competing financial interest.
REFERENCES
■
(1) Spiegel, S.; Milstien, S. The outs and the ins of sphingosine-1-
phosphate in immunity. Nat. Rev. Immunol. 2011, 11, 403−415.
(2) Cyster, J. G. Chemokines, sphingosine-1-phosphate, and cell
migration in secondary lymphoid organs. Annu. Rev. Immunol. 2005,
23, 127−159.
(3) Mutoh, T.; Rivera, R.; Chun, J. Insights into the pharmacological
relevance of lysophospholipid receptors. Br. J. Pharmacol. 2012, 165,
829−844.
(4) Chi, H. Sphingosine-1-phosphate and immune regulation
trafficking and beyond. Trends Pharmacol. Sci. 2011, 32, 16−24.
(5) Brinkmann, V. Sphingosine 1-phosphate receptors in health and
disease: Mechanistic insights from gene deletion studies and reverse
pharmacology. Pharmacol. Ther. 2007, 115, 84−105.
(6) Rosen, H.; Gonzalez-Cabrera, P. J.; Sanna, M. G.; Brown, S.
Sphingosine-1-phosphate receptor signaling. Annu. Rev. Biochem. 2009,
78, 743−768.
(19) For a recent review: Bolli, M. H.; Lescop, C.; Nayler, O.
Synthetic sphingosine 1-phosphate receptor modulatorsOpportu-
nities and potential pitfalls. Curr. Top. Med. Chem. 2011, 11, 726−757.
(20) Gergely, P.; Nuesslein-Hildesheim, B.; Guerini, D.; Brinkmann,
V.; Traebert, M.; Bruns, C.; Pan, S.; Gray, N. S.; Hinterding, K.;
Cooke, N. G.; Groenewegen, A.; Vitality, A.; Sing, T.; Luttringer, O.;
Yang, J.; Gardin, A.; Wang, N.; Crumb, W. J., Jr; Saltzman, M.;
(7) Brinkmann, V.; Billich, A.; Baumruker, T.; Heining, P.;
Schmouder, R.; Francis, G.; Aradhye, S.; Burtin, P. Fingolimod
(FTY720): Discovery and development of an oral drug to treat
multiple sclerosis. Nat. Rev. Drug Discovery 2010, 9, 883−897.
(8) Mandala, S.; Hajdu, R.; Bergstrom, J.; Quackenbush, E.; Xie, J.;
Milligan, J.; Thornton, R.; Shei, G.; Card, D.; Keohane, C.; Rosenbach,
M.; Hale, J.; Lynch, C. L.; Rupprecht, K.; Parsons, W.; Rosen, H.
Alteration of lymphocyte trafficking by sphingosine-1-phosphate
receptor agonists. Science 2002, 296, 346−349.
(9) Brinkmann, V.; Davis, M. D.; Heise, C. E.; Albert, R.; Cottens, S.;
Hof, R.; Bruns, C.; Prieschl, E.; Baumruker, T.; Hiestand, P.; Foster, C.
A.; Zollinger, M.; Lynch, K. R. The immune modulator FTY720
targets sphingosine-1-phosphate receptors. J. Biol. Chem. 2002, 277,
21453−21457.
Rosenderg, M.; Wallstrom, E. The selective S1P receptor modulator
̈
BAF312 redirects lymphocyte distribution and has species-specific
effects on heart rate: translation from preclinical to clinical studies. Br.
J. Pharmacol. 2012, 167, 1035−1047.
(21) Pan, S.; Mi, Y.; Pally, C.; Beerli, C.; Chen, A.; Guerini, D.;
Hinterding, K.; Nuesslein-Hildesheim, B.; Tuntland, T.; Lefebvre, S.;
Liu, Y.; Gao, W.; Chu, A.; Brinkmann, V.; Bruns, C.; Streiff, M.;
Cannet, C.; Cooke, N.; Gray, N. Chem. Biol. 2006, 13, 1227−1234.
(22) Hanson, M. A.; Roth, C. B.; Jo, E.; Griffith, M. T.; Scott, F. L.;
Reinhart, G.; Desale, H.; Clemons, B.; Cahalan, S. M.; Schuerer, S. C.;
Sanna, M. G.; Han, G. W.; Kuhn, P.; Rosen, H.; Stevens, R. C. Crystal
structure of a lipid G-protein-coupled receptor. Science 2012, 335,
851−855.
(10) Matloubian, M.; Lo, C. G.; Cinamon, G.; Lesneski, M. J.; Xu, Y.;
Brinkmann, V.; Allende, M. L.; Proia, R. L.; Cyster, J. G. Lymphocyte
dgress from thymus and peripheral lymphoid organs is dependent on
S1P receptor 1. Nature 2004, 427, 355−360.
(11) Cyster, J. G. Chemokines, sphingosine-1-phosphate, and cell
migration in secondary lymphoid organs. Annu. Rev. Immunol. 2005,
23, 127−159.
(12) Schmouder, R.; Serra, D.; Wang, Y.; Kovarik, J. M.; DiMarco, J.;
Hunt, T. L.; Bastien, M.-C. FTY720: Placebo-controlled study of the
effect on cardiac rate and rhythm in healthy subjects. J. Clin.
Pharmacol. 2006, 46, 895−904.
(13) Forrest, M.; Sun, S.-Y.; Hajdu, R.; Bergstrom, J.; Card, D.;
Doherty, G.; Hale, J.; Keohane, C.; Meyers, C.; Milligan, J.; Mills, S.;
Nomura, N.; Rosen, H.; Rosenbach, M.; Shei, G.-J.; Singer, I. I.; Tian,
M.; West, S.; White, V.; Xie, J.; Proia, R. L.; Mandala, S. Immune cell
regulation and cardiovascular effects of sphingosine-1-phosphate
receptor agonists in rodents are mediated via distinct receptor
subtypes. J. Pharmacol. Exp. Ther. 2004, 309, 758−768.
(14) Sanna, M. G.; Liao, J.; Jo, E.; Alfonso, C.; Ahn, M.-Y.; Peterson,
M. S.; Webb, B.; Lefebvre, S.; Chun, J.; Gray, N.; Rosen, H.
Sphingosine-1-phosphate (S1P) receptor subtypes S1P1 and S1P3,
E
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