Discovery of a Series of Indole-2 Carboxamides as Selective Secreted Phospholipase A2 Type X (sPLA2-X) Inhibitors

Article abstract of DOI:10.1021/acsmedchemlett.7b00505

In order to assess the potential of sPLA₂-X as a therapeutic target for atherosclerosis, novel sPLA₂ inhibitors with improved type X selectivity are required. To achieve the objective of identifying such compounds, we embarked on a lead generation effort that resulted in the identification of a novel series of indole-2-carboxamides as selective sPLA2-X inhibitors with excellent potential for further optimization.

Full text of DOI:10.1021/acsmedchemlett.7b00505

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Letter
Discovery of a series of indole-2 carboxamides as selective
secreted phospholipase A2 type X (sPLA2-X) inhibitors
Laurent Knerr, Fabrizio Giordanetto, Peter Nordberg, Daniel Pettersen, Nidhal Selmi, Hans-
Georg Beisel, Hannah de la Motte, Thomas Olsson, Tim D.J. Perkins, Margareta Herslöf, Åsa
Månsson, Mikael Dahlstrom, Ingemar Starke, Johan Broddefalk, Gabrielle Saarinen, Fredrik
Klingegård, Eva Hurt-Camejo, Birgitta Rosengren, Johan Brengdahl, Frank Jansen, Mattias
Rohman, Jenny Sandmark, Kenth Hallberg, Tomas Akerud, Robert G. Roth, and Marie Ahlqvist
ACS Med. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acsmedchemlett.7b00505 • Publication Date (Web): 23 Jun 2018
Downloaded from http://pubs.acs.org on June 25, 2018
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ACS Medicinal Chemistry Letters
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Discovery of a series of indoleꢀ2 carboxamides as selective
secreted phospholipase A2 type X (sPLA2ꢀX) inhibitors
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Laurent Knerra*, Fabrizio Giordanettoa*,†, Peter Nordberga, Daniel Pettersena, Nidhal Selmia, HansꢀGeorg Beisela,#, Hannah
de la Mottea,¤, Thomas Olssona,‡, Tim D. J. Perkinsa, Margareta Herslöfa, Åsa Månssona,Ø, Mikael Dahlströma, Ingemar
Starkea, Johan Broddefalka, Gabrielle Saarinena,§, Fredrik Klingegårda,¶, Eva HurtꢀCamejob, Birgitta Rosengrenc, Johan
Brengdahld, Frank Jansene, Mattias Rohmand, Jenny Sandmarkf, Kenth Hallbergf,‡, Tomas Åkerudf, Robert G. Rothf, Marie
Ahlqvistg
aMedicinal Chemistry, bTranslational Sciences, cBioscience and gDrug Metabolism and Pharmacokinetics,
Cardiovascular and Metabolic Diseases, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden.
dReagents and Assay Development, eMechanistic Biology and Profiling, fStructure and Biophysics, Discovery Sciences,
IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden.
KEYWORDS. secreted phospholipase A2 type X; inhibitor; X-ray crystallography; atherosclerosis; coronary artery disease
ABSTRACT: In order to assess the potential of sPLA2ꢀX as a therapeutic target for atherosclerosis novel sPLA2 inhibitors with
improved type X selectivity are required. To achieve the objective of identifying such compounds, we embarked on a lead generaꢀ
tion effort that resulted in the identification of a novel series of indoleꢀ2ꢀcarboxamides as selective sPLA2ꢀX inhibitors with excelꢀ
lent
potential
for
further
optimisation.
Secreted phospholipases A2 (sPLA2s) are structurally conꢀ
served enzymes catalyzing the hydrolysis of glycerophosphoꢀ
lipids at the snꢀ2 position, leading to the production of free
fatty acids and lysophospholipids.1 Accumulating evidence
indicates that several sPLA2 isoforms, namely IIA (sPLA2ꢀ
IIA), sPLA2ꢀIII, sPLA2ꢀV and sPLA2ꢀX play significant, disꢀ
tinct, or overlapping roles in one or several steps of atherogenꢀ
esis.2 This led to the clinical testing of Aꢀ002 (varespladib
methyl) (Figure 1), a nonselective inhibitor of sPLA2ꢀIIA,
sPLA2ꢀV and X isoforms, for the treatment of coronary artery
disease.3 Group X sPLA2 (sPLA2ꢀX) is structurally related to
other sPLA2 isoforms and, among these, it is the most potent at
hydrolyzing phosphatidylcholine, a highly abundant phosphoꢀ
lipid at the cell surface and on lipoproteins.4,5 This enzyme is
expressed in atherosclerotic lesions and peripheral blood
cells.6 In vitro and in vivo studies have reported proꢀ
atherogenic properties of sPLA2ꢀX comprising lipoprotein
modifications leading to foam cell formation, reduced cell
cholesterol efflux, altered immune cells maturation and vascuꢀ
lar cells proliferation.7ꢀ10 These effects indicate that sPLA2ꢀX is
a potential novel therapeutic target for the treatment of cardioꢀ
vascular diseases.2 On the other hand, an in vivo study in a
mouse model of atherosclerosis has shown that expression of
sPLA2ꢀX in bone marrow cells limits the development of
atherosclerosis.11 Additionally, the VISTAꢀ16 (Vascular Inꢀ
flammation Suppression to Treat Acute Coronary Syndrome)
phase III trial, showed that administration of varespladib meꢀ
thyl did not reduce the occurrence of acute coronary synꢀ
drome (ACS) events but significantly increased the risk of
nonfatal myocardial infarction.12 These results could indicate
that a broad spectrum sPLA2 inhibitor may be detrimental in
atherosclerotic cardiovascular disease. Alternatively, novel
sPLA2 inhibitors with improved potency, safety and selectivity
would be required to demonstrate a therapeutic benefit in
atherosclerotic conditions. The availability of isoformꢀ
selective sPLA2 inhibitors could help dissecting the individual
contribution of different sPLA2 enzymes in proꢀ and antiatherꢀ
ogenic mechanisms. We therefore embarked on a discovery
effort aiming at generating sPLA2ꢀX inhibitors13 possessing
30 fold selectivity over other sPLA2 subtypes and suitable for
oral administration. The lead generation part of this project
will be described here.
A combination of NMR screening and high throughput screenꢀ
ing (HTS) of the AstraZeneca compound collection was deꢀ
vised to identify chemical starting points with the potential to
deliver selective inhibitors of sPLA2ꢀX (see supporting inforꢀ
mation for a more detailed description). This resulted in the
identification of indole carboxamide 1 as a low micromolar
inhibitor of sPLA2ꢀX (Figure 1).
Figure 1. sPLA2 inhibitor Varespladib Methyl, its active
metabolite Varespladib and initial hit 1.
A crystal structure of 1 bound to sPLA2ꢀX was solved and
showed that the carboxamide group of 1 established three
hydrogen bonds and one coordination bond with the protein
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ACS Medicinal Chemistry Letters
and the catalytic calcium ion, respectively (Figure 2), similar
Page 2 of 7
that, in a number of sPLA2ꢀX crystal structures available to
our team, a water molecule or component of the crystallisation
buffer were found to coordinate the calcium ion in close proxꢀ
imity to the area occupied by the trifluoromethyl group of 1.
We therefore decided to focus on this position for introducing
structural elements compatible with a second calcium interacꢀ
tion. Introduction of a carboxylic acid group in the meta posiꢀ
tion resulted in measurable inhibition of sPLA2ꢀX (3, Table 1).
Atomic spacers between the aryl and carboxylic acid group
improved the activity three fold for methylene (4) and thirty
fold for the ethylene resulting in the first submicromolar
sPLA2ꢀX inhibitor, endowed with high ligand and ligand
lipophilicity efficiencies (5, Table 1). Based on this result and
to further validate our modelling results modification of the
ethyl spacer by rigidification through unsaturation (6) or variaꢀ
tion of the phenyl anchoring moiety using ether (7) or amide
(8) groups was attempted but turned out to be poorly tolerated
with seven to twentyꢀseven fold loss of sPLA2ꢀX inhibitory
activity. Initial attempt of functionalising the indole core by Nꢀ
benzylation instead of Nꢀarylation proved counterproductive
as well (9, Table 1). Replacement of the carboxylic acid group
by a primary amide (10) yielded a complete loss of inhibition,
while an acylsulfonamide bioisosteric element (11) was tolerꢀ
ated albeit with a five fold reduction in potency, indicating
specific spatial and electronic restraints for the coordination of
the calcium ion. Having identified 5 as a promising sPLA2ꢀX
inhibitor, we assessed the importance of the indole system (see
Table S1 in the supporting information). Truncation of the
indole to a pyrrole ring (12) highlighted the requirement of a
bicyclic system for sPLA2ꢀX inhibition. Introduction of polariꢀ
ty using 7ꢀazaindole (13) or imidazo[1,2ꢀa] pyridine (14)
scaffolds was not tolerated. Conservative changes using
thienopyrrole cores (15, 16) also resulted in total loss of inhibꢀ
itory activity. Partial reduction of the indole core by saturation
of the phenyl ring (17) was tolerated although this reduced
sPLA2ꢀX inhibition sixꢀfold. Based on these results, we resortꢀ
ed to use the indole scaffold of 5 as the basis for further moꢀ
lecular designs to explore the impact of indole substituents on
both potency and selectivity. Systematic introduction of meꢀ
thyl groups (18–21, Table 2) indicated position 6 on the indole
core as the most favourable for further optimization, due to the
four fold sPLA2ꢀX inhibition improvement over 5 and the
structural data available. Here, improvement of potency via
introduction of electron withdrawing and lipophilic substituꢀ
ents such as chloride (23) and trifluoromethyl (24) yielded
encouraging sPLA2ꢀX inhibitory activity when using high
density lipoprotein (HDL) as a more diseaseꢀrelevant sPLA2ꢀX
substrate (Table 2). Further biological screening indicated that
more voluminous substituents of electron donating nature (i.e.,
ethyl (25), cyclopropyl (26) and methoxy (27)) did not offer
any advantages over methyl. Introduction of polarity via hyꢀ
droxymethyl (28) and cyano (29) substituents did not result in
any further potency gains. Based on these emerging structure
activity relationships, we targeted bulkier substituents with
electron withdrawing character. Specifically, trifluoromethoxy
(31) proved superior to difluromethoxy (30) and 2,2,2ꢀ
trifluoroethoxy (32) alternatives (Table 3).
to analogous interactions reported in the literature,14 highlightꢀ
ing the importance of primary amides as warheads for sPLA2
inhibition. The indole core of 1 occupies a hydrophobic pocket
lined by residues Leu5, Val9, Pro17, Tyr20, Cys43, Ile94 and
Leu98. Interestingly, this lipophilic pocket differs across
sPLA2 isoforms. In sPLA2ꢀIIa, the most closely related isoꢀ
form to sPLA2ꢀX, Leu5, Val9 and Leu98 are replaced by Phe,
Ile and Phe, respectively (Figure 2). We hypothesized that
these differences in side chain sizes could effectively result in
difference in pocket sizes thus potentially offering a design
manifold to improve sPLA2 isoform selectivity by modifyꢀ
ing/substituting the phenyl part of the indole core. The metaꢀ
trifluoromethyl phenyl group of 1 is involved in hydrophobic
interactions with Ile2, Leu5, Gly28, Leu29, Tyr50 and Lys61.
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Figure 2. Crystal structure of sPLA2ꢀX in complex with comꢀ
pound 1 (orange). The amide of 1 forms three hydrogen bonds
to the protein (2.7ꢀ3.1 Å) and one coordination bond to the
calcium ion (2.5 Å), all marked by dashed lines.
Based on this structural framework, we set out to improve
both the inhibitory potency and the selectivity versus the most
widely abundant sPLA2 isoforms IIa and V. Ligand efficiency
(LE) and ligandꢀlipophilicity efficiency (LLE) were carefully
monitored during this process to ensure that, despite the lipoꢀ
philic nature of the binding pocket, lipophilicity and molecular
properties would be kept in line with oral bioavailability poꢀ
tential. As a first step, we embarked on derivatizing the termiꢀ
nal Nꢀaryl ring substituting the indole nitrogen atom of 1 with
a view to establishing a second ligand interaction with the
calcium ion. We reasoned this design hypothesis could have
resulted in improved sPLA2 inhibition while affording a more
balanced physical chemical profile compatible with adequate
solubility and metabolic stability by virtue of the envisioned
polar chelating groups. Here, based on available data,14ꢀ18
special emphasis was placed on carboxylic acids/bioisosteres,
as summarized in Table 1. The unsubstituted Nꢀphenylꢀ
containing derivative (2) was essentially inactive. We noticed
2
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Table 1. sPLA2ꢀX potency and ligand efficiencies for comꢀ
pounds 1ꢀ11
X)/2.303.Heavy Atom Count using R=0.001987 kcal.molꢀ1.Kꢀ1
and T=298K. Ligand Lipophilicity efficiency (LLE) calculated
as ꢀpIC50(sPLA2ꢀX) – measured logD7.4.
c Not Determined
1
2
3
4
d Top concentration tested : 30µM
5
6
7
8
The crystal structure of sPLA2ꢀX and 31 confirmed the bidenꢀ
tate calcium interaction by the carboxamide and carboxylic
groups (Figure 3). The carboxylic acid of 31 that also forms an
additional hydrogen bond to the main chain nitrogen of Gly30.
The ethylene linker utilizes a narrow space defined by the side
chains of Asp47, Tyr50 and Lys61. One side of the phenyl
substituent is stacking against the main chains of Gly28 and
Leu29. The trifluoromethoxy substituent is accommodated in a
hydrophobic pocket with extensive van der Waals contacts
(distances 3.6ꢀ4.0 Å) to the side chains of Ile2, Ala6, Pro17,
Ile18 and Met21. The binding mode of the indole core was
unaltered compared to 1 and, as hypothesized, sequence comꢀ
parison between the sPLA2ꢀX, ꢀIIa and ꢀV suggests that resiꢀ
dues in the indole binding pocket are likely to be determinants
for isoform selectivity (Figure 3A) by preventing the indole
core from adopting the same binding mode, as reflected by the
lower affinity of 31 for these isoforms (11 and 85 fold reduced
potency to sPLA2ꢀX, respectively, Table 3).
sPLA2ꢀX
IC50 (ꢁM)a,d
0.041
R1
LE/LLEb
9
varespladib
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
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42
43
44
45
46
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6.9
0.32/1
<0.34/NDc
0.29/4.5
0. 30/4.8
0.35/5.6
2
3
4
5
>30
29.1
10.3
0.99
Table 2. sPLA2ꢀX potency and ligand efficiencies for comꢀ
pound 18 – 32.
6
7
23.6
26.9
0.27/4.2
0.27/4.5
R
sPLA2ꢀ sPL sPLA2ꢀV LE/LLEb
X
A2ꢀ
IIa
IC50
IC50
(HDL)
IC50
(ꢁM)a
(ꢁM)a (ꢁM)
a
0.012
0.041
(0.15)
0.124
Varesꢀ
pladib
5
0.36/6.6
8
9
7.2
20.7
>30
0.28/5.1
0.29/4.6
H
0.99
0.83
2.7
NAc
ꢀ
NAc
ꢀ
0.37/5.9
0.35/5.3
0.32/4.8
0.38/5.8
0.33/5.2
0.36/6.0
4ꢀMe
5ꢀMe
6ꢀMe
7ꢀMe
6ꢀF
18
19
20
21
22
ꢀ
ꢀ
0.23
1.9
NAc
NAc
NAc
5.7
NAc
NAc
NAc
NAc
10
<0.26/<3.3
0.26
0.09
6ꢀCl
0.4/6.0
23
(1.1)
0.043
(0.48)
0.89
3.7
6ꢀCF3
6ꢀEt
0.37/5.9
0.37/5.5
0.36/5.5
24
25
26
11
4.8
0.25/4.6
0.17
4.4
2.3
NAc
>10
a
0.16
(1.9)
Results are mean of at least two experiments. Experimental
errors within 20% of value [enzyme]. Substrate composition :
50 mg of 1ꢀpalmitoylꢀ2ꢀoleoylꢀsnꢀglyceroꢀ3ꢀphosphocholine
(Avanti Polar Lipids 850457P) in 1ml 4% NonidetP40 (USB)
and 2% deoxycholic acid (Sigma D6750)).
6ꢀcPr
6ꢀOMe
0.62
2.8
NAc
NAc
3.9
NAc
NAc
NAc
0.33/5.9
0.3/5.6
27
28
6ꢀCH2OH
b Ligand efficiency (LE) is expressed in units of kcal·mol−1 per
nonꢀhydrogen atom and calculated as –ꢀRTpIC50(sPLA2ꢀ
0.11
(0.99)
6ꢀCN
0.37/6.7
29
3
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arylation was performed using two different copper based
0.068
(0.37)
3.6
0.31
>10
NAc
6ꢀOCF2H
6ꢀOCF3
0.36/6.2
0.36/6.0
0.33/5.6
30
31
32
methods.20,21 The intermediate acids were then converted to
primary amides before final removal of the tertꢀbutyl ester
protecting group. This synthetic sequence produced only modꢀ
est to good overall yields but proved robust enough for the
rapid generation of arrays of diverse derivatives presented
here.
1
2
3
4
5
6
7
8
0.026
(0.27)
2.23
NAc
0.093
(0.74)
6ꢀOCH2CF3
a
Results are mean of at least two experiments. Experimental
errors within 20% of value [enzyme]. Substrates compositions
i) PC 50 mg of 1ꢀpalmitoylꢀ2ꢀoleoylꢀsnꢀglyceroꢀ3ꢀ
Scheme 1. General synthesis of indoleꢀ2 carboxamides derivaꢀ
tives.a
:
9
phosphocholine (Avanti Polar Lipids 850457P) in 1ml 4%
NonidetP40 (USB) and 2% deoxycholic acid (Sigma D6750))
ii) HDL : HDL isolated from human plasma by ultracentrifuꢀ
gation was used as substrate.
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b Ligand efficiency (LE) is expressed in units of kcal·mol−1 per
nonꢀhydrogen atom and calculated as –ꢀRTpIC50(sPLA2ꢀ
X)/2.303.Heavy Atom Count using R=0.001987 kcal.molꢀ1.Kꢀ1
and T=298K. Ligand Lipophilicity efficiency (LLE) calculated
as ꢀpIC50(sPLA2ꢀX) – measured logD7.4.
c Not active at highest tested concentration (30µM).
While some close derivatives possessed better selectivity
profiles (e.g. 30 and 32), 31 demonstrated improved lipolitic
activity of sPLA2ꢀX on HDL (IC50: 270 nM) and was thereꢀ
fore profiled further. 31 did not display any significant binding
to a large panel of biological targets and no significant inhibiꢀ
tion of ion channels, enzymes and transporters that might be
related to toxicity (Table 3). While the aqueous solubility and
passive permeability of 31 were adequate, its in vitro metabolꢀ
ic stability was subꢀoptimal, and this readily translated in
sufficient oral bioavailability but high unbound clearance.
These properties made 31 inadequate as a tool compound for
in vivo evaluation due to too high doses required to cover IC50
and IC90 but offered clear avenues for further optimisation.
a Reagents and conditions : a) Cu(OAc)2 (1 eq.), DBU (3 eq.),
DMSO, µw 140°Cꢀ150°C. b) CuI (0.2 eq.), piperidineꢀ2ꢀ
carboxylic (0.4 eq.), K2CO3 (3 eq.), DMF, 110°C. c) NH4Cl (3
eq.), TBTU (1.5 eq.), DIEA (9 eq.), DMF, rt. d) 4M HCl in
1,4ꢀdioxane, rt. e) LiOH, THF, water, rt.
In summary, starting from the indole carboxamide hit 1, a
series of structureꢀbased, medicinal chemistry explorations
resulted in the identification of derivative 31, a novel sPLA2ꢀX
inhibitor with favourable properties for further investigation.
The optimisation of its selectivity and in vivo pharmacokinetic
profile towards sPLA2ꢀXꢀcentric, preclinical proof of concept
studies in animals is detailed in the accompanying paper.
Table 3. Profiling of compound 31a
Solubility (pH=7.4) (µM)
Cacoꢀ2 Papp (10ꢀ6 cm/s)
98
18.8
ASSOCIATED CONTENT
Human Hepatocytes Clint
(ꢁL/min/10ꢀ6 cells)
1.7
Supporting Information
The Supporting Information is available free of charge
on the
Experimental details, synthesis, assay protocols
and Xꢀray crystallographic statistics (PDF)
Accession codes
PDB code for the Xꢀray crystal structure described in this
study has been deposited in the Protein Data Bank under
the accession codes 5OW8 and 5OWC.
sPLA2ꢀX IC50 (µM)
sPLA2ꢀX mouse IC50 (µM)
sPLA2ꢀIIa IC50 (µM)
sPLA2ꢀV IC50 (µM)
0.026
0.096
0.31
2.23
Pharmacokinetics
Rat
Dog
Dose i.v./p.o. (µmol/kg)
CL (mL/min/kg)
AUC (µM.h)
Vdss (L/kg)
1/4
9.1
1/ꢀ
0.75
1.84/11 8.78/ꢀ
AUTHOR INFORMATIONS
Correponding authors
2.54
0.44
F (%)
100
aSee supporting information for experimental details
*(LK)
Tel.:
+46317065788.
Email
:
lauꢀ
The indole 2ꢀcarboxamides derivatives were efficiently preꢀ
pared by liquid phase parallel synthesis using the approach
described in scheme 1. Starting from commercially available
or readily accessible19 indoleꢀ2ꢀcarboxylic acids, the Nꢀ
rent.knerr@astrazeneca.com
*(FG) Tel.: +1 (212) 478 0822. Email : fabꢀ
rizio.giordanetto@DEShawResearch.com
4
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The authors would like to acknowledge the support of the
Present adresses :
1
2
3
†F.G: D.E. Shaw Research, 120W 45th Street, New York, New
Structure Analysis and Separation Science group of Astraꢀ
Zeneca Gothenburg.
York 10036, United States
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Figure 3. A) Sequence alignment of mature sPLA2ꢀX (top), ꢀIIa (middle) and –V (bottom). Black arrows mark residues
that interact with the indole core. Blue arrows indicate residues make up the hydrophobic pocket that harbours the trifluoꢀ
romethoxy moiety. Red arrows highlight residues predicted to be determinants of sPLA2 isoform selectivity. B) Superpoꢀ
sition of crystal structures of sPLA2ꢀX in complex with 1 (orange) and 31 (green). The structure shows that the carboxyl
group of 31 forms the second interaction to the calcium ion. Three residues are marked in red (Leu5, Val9 and Ile94), as
they are predicted to be responsible for isoform selectivity. C) Crystal structure of sPLA2ꢀX in complex with 31. Residues
lining the lipophilic pocket that harbours the trifluoromethoxy moiety are labelled.
Abꢀ
breꢀ
#HꢀG.B.: Medivir AB, Huddinge, Sweden
¤H.d.l.M.: RISE Research Institutes of Sweden Division Bioeꢀ
viations used :
conomy, Gothenburg, Sweden.
sPLA2, secreted phospholipase 2; VISTA, Vascular Inflamꢀ
mation Suppression to Treat Acute Coronary Syndrome; HTS,
high throughput screening; ACS, acute coronary syndrome;
PC, phosphatidylcholine; HDL, high density lipoprotein; LE,
‡T.O.: Gothenburg University
ØÅ.M.: Alfa Laval Lund AB, Lund, Sweden
§G.S.: SCA Hygiene products AB, Stockholm, Sweden.
¶F.K.: SciLifeLab, Drug Discovery & Development Platform,
Solna, Sweden.
Ligand Efficiency, LLE, Lipophilicity Ligand Efficiency; Papp
,
apparent permeability ; Clint, intrinsic clearance; i.v., intraveꢀ
nous; p.o., per oral; CL, clearance; AUC, area under curve;
Vdss, steady state volume of distribution; F, oral bioavailabilꢀ
ity; DBU, 2,3,4,6,7,8,9,10ꢀoctahydropyrimido[1,2ꢀa]azepine;
DMSO, dimethyl sulfoxide; DMF, dimethylformamide;
TBTU, 2ꢀ(1Hꢀbenzo[d][1,2,3]triazolꢀ1ꢀyl)ꢀ1,1,3,3ꢀ v tetrameꢀ
thylisouronium tetrafluoroborate; DIEA, diisopropylethylaꢀ
mine.
‡K.H.: SARomics Biostructures, Lund, Sweden.
Notes
The authors declare no competing financial interests
ACKNOWLEDGMENTS
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sPLA2-X IC50 : 6900nM
sPLA2-X IC50 : 26nM
sPLA2-IIa IC50 : 310nM
sPLA2-V IC50 : 2230nM
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